Draft California 2026 Integrated Report (303(d) List/305(b) Report)

Supporting Information

Regional Board 6 - Lahontan Region

Water Body Name:	Susan River (Headwaters to Willard Crk)
Water Body ID:	CAR6372001020080815005311
Water Body Type:	River & Stream


DECISION ID	75228	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Mercury
Final Listing Decision:	Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)(2016)
Revision Status	Revised
Reason for Delisting:	Delisting due to spatial change or other CalWQA administrative reason
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the CWA section 303(d) List under section 4.11 of the Listing Policy. Under this section when all other delisting factors do not result in the delisting of a water segment but information indicates attainment of standards, a water segment shall be evaluated to determine whether the weight of evidence demonstrates that water quality standard is attained. If the weight of evidence indicates attainment, the water segment shall be removed from the CWA section 303(d) List. The State Water Board listed the entire Susan River for mercury during the 2006 assessment cycle on the basis of trout tissue samples that exceeded OEHHA fish consumption criteria. The trout were collected at stations above and below Susanville. The river was later divided into three segments for the 2008 assessment cycle, and the original mercury listing was applied to all three of the resulting segments at that time. The Susan River was re-segmented during the 2018 cycle. As a result of the change in the segmentation together with the adoption of a statewide mercury objective in 2017, mercury tissue data were reassessed, and where necessary, data collected in different segments of the river was separated to allow an accurate depiction of where mercury impairments may exist. LOE# 6686 contains the original data used to list the river but it is replaced by LOE 133373 and 13374 which are based on only the data collected in this segment assessed against the new mercury objective. LOE 6686 is not included in the final use support rating. Two lines of evidence are available in the administrative record to assess this pollutant for COMM and WILD. One of two samples exceed the mercury tissue objective for COMM and one of two samples exceed the mercury tissue objective for WILD. Based on this result, there is evidence to suggest that impairment due to mercury may be occurring however there is insufficient data to place the waterbody into category 5. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for removing this water segment-pollutant combination from the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The following information indicates that the water quality standard is attained. One of two samples exceed the mercury tissue objective for COMM and one of two samples exceed the mercury tissue objective for WILD. 3. Due to the re-segmentation of the Susan River and reassessment of the available data for mercury, there is no longer sufficient justification to place this waterbody on the CWA section 303(d) list. 4. This process is scientifically defensible and reproducible.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be removed from the section 303(d) list because the original basis for listing was flawed. This is because the data used to list the Susan River was collected in two different segments of the river and when reassessed against the current mercury tissue objective, the resulting exceedance count does not result in listing this segment.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 75228, Mercury	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

133373

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fish tissue analysis

Data Used to Assess Water Quality:

Water Board staff assessed data from the Toxic Substances Monitoring Program for the Susan River to determine beneficial use support and the results are as follows: 1 of 2 samples exceed the water quality objective for Mercury. This line of evidence contains data only for trophic level 3 fish. The concentration of mercury in fish collected with the same calendar year, for the same trophic level were averaged into a single sample for comparison with the objective. A total of six fish were aggregated into each annual average, which consisted of 1 fish species (Two composites of Rainbow trout each composed of six fish per composite for two annual average values).

Data Reference:

Toxic Substances Monitoring Program data for years 1992-2002 and Coastal Fish Contamination Program for years 1 and 2. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Lahontan RWQCB Basin Plan: All waters shall be maintained free of toxic substances in concentrations that are toxic to, or produce detrimental physiological responses in human, plant, animal, or aquatic life.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The Statewide Sport Fish Water Quality Objective for the protection of Wildlife Habitat comes from the Statewide Water Quality Control Plan for Inland Surface Waters, Enclosed Bays, and Estuaries of California, and is 0.2 mg/Kg wet weight skinless fillet samples of trophic level 3, or trophic level 4 fish (whichever is highest in the water body) over a one year averaging period. If trophic level 3 fish are used in the assessment then the Prey Fish Water Quality Objective must also be used to determine that the Sport Fish Objective is being met. Trophic levels of applicable fish are defined in, but not limited to those in Attachment C of the Final Regulatory Language document (Appendix A) of State Water Resources Control Board Resolution No. 2017-0027.

Guideline Reference:

Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy

Spatial Representation:

One station was sampled: upstream of Susanville, station code 637ST1736.

Temporal Representation:

Samples were collected on 10/16/1999 and 10/22/1999.

Environmental Conditions:

QAPP Information:

Environmental Chemistry Quality Assurance and Data Report for the Toxic Substances Monitoring Program, 1996-2000. Department of Fish and Game.

QAPP Information Reference(s):

This is a placeholder for previously assessed data that does not have quality assurance information but would require it under newly developed policies. These LOEs were previously assessed and approved at the Regional, State and Federal level in past cycles. The LOEs needed to be moved and/or reassessed but required this reference code for movement within the decision making database.

Line of Evidence (LOE) for Decision ID 75228, Mercury	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

6686

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fish tissue analysis

Data Used to Assess Water Quality:

Two out of 4 samples exceeded. Four filet composite samples, two each, of rainbow trout and brook trout were collected. Rainbow trout were collected in 1998-99. Brook trout were collected in 1999 and 2001. The 1999 rainbow and brook trout samples exceeded the guideline. Both sampled stations exceeded the guideline in 1999 (TSMP, 2002).

Data Reference:

Placeholder reference 2006 303(d)

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Placeholder reference 2006 303(d)

Evaluation Guideline:

OEHHA Screening Value 0.3 μg/g (Brodberg & Pollock, 1999).

Guideline Reference:

Placeholder reference 2006 303(d)

Spatial Representation:

Two stations were sampled: just upstream of HWY 36 bridge on the Susan River (Susanville) and downstream of Piute Creek mouth at Alexander Street bridge (Piute Creek).

Temporal Representation:

Samples were collected annually in 1998-99 and 2001.

Environmental Conditions:

QAPP Information:

Environmental Chemistry Quality Assurance and Data Report for the Toxic Substances Monitoring Program, 1996-2000. Department of Fish and Game.
Environmental Chemistry Quality Assurance and Data Report for the Toxic Substances Monitoring Program, 2001-2002. Department of Fish and Game.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 75228, Mercury	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

133374

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Total

Beneficial Use:

Wildlife Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fish tissue analysis

Data Used to Assess Water Quality:

Data Reference:

Toxic Substances Monitoring Program data for years 1992-2002 and Coastal Fish Contamination Program for years 1 and 2. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy

Spatial Representation:

One station was sampled: upstream of Susanville, station code 637ST1736.

Temporal Representation:

Samples were collected on 10/16/1999 and 10/22/1999.

Environmental Conditions:

QAPP Information:

Environmental Chemistry Quality Assurance and Data Report for the Toxic Substances Monitoring Program, 1996-2000. Department of Fish and Game.

QAPP Information Reference(s):


DECISION ID	162258	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Toxicity
Final Listing Decision:	Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Delist from 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Reason for Delisting:	Delisting due to spatial change or other CalWQA administrative reason
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	(The decision is called "delist" due to database rules, since this pollutant was listed in the past. The action the Board is taking in this cycle is actually "do not list") The Susan River as a whole was listed for "Unknown Toxicity" in the 1990s based on data from a US EPA study. The river was divided into segments for the 2008 cycle and the original decision was copied to all three segments. For the 2018 assessment cycle the waterbody was again remapped to better reflect the known land uses in the watershed. A 2004 University of California Davis study confirmed that toxicity was still present in portions of the river but that data was not collected in this segment of the river, rather the sample sites were located in the Willard Creek to Susanville segment. Two lines of evidence are now available in the administrative record to assess this pollutant. One LOE assesses the available data against the COLD beneficial use, and one LOE assesses the available data against the WARM beneficial use. Zero of 3 samples exceed the water quality criteria for both beneficial use assessments. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 3 samples exceed the water quality criteria for both the COLD and WARM beneficial use assessments and these sample sizes are insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. A minimum of 26 samples per beneficial use assessed are needed to determine if a beneficial use is fully supported using table 3.1. 4. Pursuant to SECTION 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met."

Regional Board Decision Recommendation:	This waterbody was remapped for the 2018 assessment cycle. Consequently, the LOEs that formed the basis for the original decision are now located in the downstream segment. Newly available data in the 2026 cycle do not support a listing for toxicity in this segment of the river.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 162258, Toxicity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

336888

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

0 of the 3 samples collected by SWAMP RWB6 Monitoring for Susan River (Headwaters to Willard Crk) exhibited toxicity. A sample may have multiple toxicity test results, but will only be counted once. A sample is defined as being collected on the same day and the same location. The following organisms and parameters were utilized for the toxicity tests: Pimephales promelas for Biomass (wt/orig indiv), Ceriodaphnia dubia for Survival, Pimephales promelas for Survival, Ceriodaphnia dubia for Young/female, Selenastrum capricornutum for Total Cell Count.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in, human, plant, animal, or aquatic life. (Lahontan Basin Plan)

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The sample is toxic when the response of the organisms exposed to the sample is significantly different (worse) than the response of the organisms exposed to the laboratory control based on statistical hypothesis testing. An exceedance is counted when the significant effect code is "Significant; Less Similarity," which means that the sample result is significantly different than the control result, and the percent effect is greater than the evaluation threshold. The default evaluation threshold is 20% unless otherwise stated."

Guideline Reference:

Short-term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater Organisms. Fourth Edition. Office of Water, U.S. Environmental Protection Agency. Washington, D.C. EPA-821-R-02-013

Spatial Representation:

The samples were collected at monitoring site: 637SUS003 ( Susan River, above confluence w/ Willard Cr ).

Temporal Representation:

The samples were collected between the dates of 2016-04-06 and 2016-06-15.

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162258, Toxicity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

336889

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at monitoring site: 637SUS003 ( Susan River, above confluence w/ Willard Cr ).

Temporal Representation:

The samples were collected between the dates of 2016-04-06 and 2016-06-15.

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162258, Toxicity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

6683

Pollutant:

Unknown Toxicity

LOE Subgroup:

Toxicity

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.

For 2008 assessment purposes, the Susan River has been split into segments. The 2006 303d placeholder LOEs apply to all new segments.

Data Reference:

Placeholder reference pre-2006 303(d)

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

QAPP Information:

Unspecified

QAPP Information Reference(s):


DECISION ID	163725	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Chloride
Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the CWA section 303(d) List under section 4.2 of the Listing Policy. Under this section a single line of evidence is necessary to assess listing status. Six lines of evidence are available in the administrative record to assess this pollutant, one that assess available data for MUN and five that assess data for COLD. 0 of the 16 samples exceed the objective for MUN, and 12 of 18 samples exceed the objective for COLD. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 12 of 18 samples exceed the objective for COLD. and this exceeds the allowable frequency listed in Table 4.2 of the Listing Policy. 4. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 163725, Chloride	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

342740

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
3 of 5 samples exceeded the water quality threshold for Chloride

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Chloride in this water body is 0.7 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2021-06-24

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163725, Chloride	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

342752

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed USFS Management Indicator Species - Streams data to determine beneficial use support and results are as follows:
0 of 1 samples exceeded the water quality threshold for Chloride

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Chloride in this water body is 0.7 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River (USFS) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163725, Chloride	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

6915

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2001 and 2005. Chloride concentrations in 16 quarterly samples ranged from below the detection level to 2.08 mg/L. The MCL was not exceeded.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for chloride is 250 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Sixteen quarterly samples (3 to 4 per year) were collected between 2001 and 2005.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The Susan River is designated for both the Warm Freshwater Habitat and Cold Freshwater Habitat beneficial uses, and for the Spawning, Reproduction and Development and Migration of Aquatic Organisms uses.

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163725, Chloride	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96628

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan field staff performing routine monitoring for the Surface Water Ambient Monitoring Program (SWAMP). Data were collected between September 2010 and November 2015. Concentrations in the raw data ranged from 0.54 to 1.4 mg/L. Six annual averages were computed, five of which exceeded the site specific objective in 2011, 2012, 2013, 2014 and 2015. Of note is the computed average in 2010 which is based on one data point only. This is of interest as 2010 reflected the only monitoring year that did not exceed the annual average.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for chloride in Susan River above Willard Creek segment, as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 0.7 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637SUS003, which is located upstream of the confluence of the Susan River with Willard Creek slightly north of Korver Road and upstream of the Highway 36 bridge.

Temporal Representation:

Data were collected beginning in September 2010 when one field visit was made. The site was again visited in June and December 2011, after which the site was visited predominantly four times per calendar year between 2012 and 2015 between early Spring and late Fall.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 163725, Chloride	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

6914

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2001 and 2005. Chloride concentrations in 16 quarterly samples (3-4 per year) ranged from below the detection level to 2.08 mg/L. One of the annual averages was an estimate; the other average values ranged from 0.71 to 1.19 mg/L. The annual average objective was exceeded in four of 5 years.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site-specific objective from Lahontan Basin Plan Table 3-9 includes an annual average chloride concentration of 0.7 mg/L and a 90th percentile value of 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Sixteen quarterly samples (3 to 4 per year) were collected between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163725, Chloride	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96659

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan field staff performing monitoring for the Surface Water Ambient Monitoring Program (SWAMP) Perennial Stream Survey. Data were collected on one occasion in August 2014. The concentration of the sample was 0.36 mg/L which did not exceed the site specific objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for chloride in the Susan River above Willard Creek segment, as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 0.7 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637PS0130, which is located 0.7 miles upstream of the confluence of the Susan River with Crazy Harry Gulch downstream of the Goumaz Campground.

Temporal Representation:

Data were collected on one occasion in August 2014.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	170409	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Nitrogen
Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the CWA section 303(d) List under section 4.2 of the Listing Policy. Under this section a single line of evidence is necessary to assess listing status. Six lines of evidence are available in the administrative record to assess this pollutant. Seventeen of 22 samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Seventeen of 22 samples exceed the water quality objective, and this exceeds the allowable frequency listed in Table 4.2 of the Listing Policy. 4. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 170409, Nitrogen	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96629

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan staff for the Surface Water Ambient Monitoring Program (SWAMP) RWB6 Monitoring program, and for a supplemental TMDL Integrated Report Special Study. The TMDL Special Study was developed by Lahontan Planning and SWAMP staff to provide additional data to the quarterly SWAMP monitoring. The purpose was to gain a better temporal understanding of levels of specific pollutants in the waterbody. To ensure the two datasets could be viably analyzed as one, the TMDL Special Study followed the same sampling protocol as SWAMP. Accordingly, the two datasets have been combined for this assessment to reflect the intended design and to best characterize conditions in the watershed. Data were collected between June 2011 and February 2017. Concentrations in the raw data ranged from 0.113 to 1.9 mg/L. Seven annual averages were computed, six of which exceeded the site specific objective (years 2012 - 2017). One sample was collected in 2011 (6/22/2011), and the resulting annual average was the only one not to exceed the water quality objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the TMDL Intergrated Report Special Study.

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for total nitrogen in the headwaters of the Susan River, as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 0.2 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637SUS003, which is located upstream of the confluence of the Susan River with Willard Creek slightly north of Korver Road and upstream of the Highway 36 bridge.

Temporal Representation:

Data were collected beginning in June 2011 when one field visit was made. Between April 2012 and December 2014 the site was visited predominantly four times per calendar year between early Spring and late Fall. In 2015 and 2016 the site was visited on a once-per-month basis. In 2017 the site was visited in January and February.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 170409, Nitrogen	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96658

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan field staff performing monitoring for the Surface Water Ambient Monitoring Program (SWAMP) Perennial Stream Survey. Data were collected on one occasion in August 2014. The concentration in the sample was 0.111 mg/L which did not exceed the site specific objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for nitrogen in the Susan River (Headwaters to Willard Creek), as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 0.2 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637PS0130, which is located 0.7 miles upstream of the confluence of the Susan River with Crazy Harry Gulch downstream of the Goumaz Campground.

Temporal Representation:

Data were collected on one occasion in August 2014.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 170409, Nitrogen	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23459

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2001 and 2005. Total nitrogen was calculated from 16 quarterly samples each for total Kjeldahl nitrogen and nitrite plus nitrate. Concentrations of total nitrogen in 16 quarterly samples included three estimated values; the remainder of the samples ranged from 0.23 and 0.66 mg/L. Two of 5 annual averages (based on 3 to 4 calcuated concentrations per year) were estimates; the remainder were 0.33, 0.30 and 0.40 mg/L. The site-specific objective was exceeded in 3 of 5 years

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The applicable site-specific objective, from Lahontan Basin Plan Table 3-9, includes an annual average total nitrogen concentration of 0.20 mg/L and a 90th percentile value of 0.30 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Sixteen quarterly samples each (3 to 4 per year) were taken for total Kjeldahl nitrogen and nitrite plus nitrate between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170409, Nitrogen	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343084

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Nitrogen, Total in this water body is 0.2 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River (USFS) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 170409, Nitrogen	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343056

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
4 of 4 samples exceeded the water quality threshold for Nitrogen, Total

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Nitrogen, Total in this water body is 0.2 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2019-12-18

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 170409, Nitrogen	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343058

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed TMDL Intergrated Report Special Study data to determine beneficial use support and results are as follows:
4 of 4 samples exceeded the water quality threshold for Nitrogen, Total

Data Reference:

WQ from the Total Maximum Daily Load for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Nitrogen, Total in this water body is 0.2 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2014-11-18 and 2017-06-14

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	163726	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Phosphorus
Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the CWA section 303(d) List under section 4.1 of the Listing Policy. Under this section a single line of evidence is necessary to assess listing status. Five lines of evidence are available in the administrative record to assess pollutant. 8 of the 18 samples exceed the objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 8 of 18 samples exceeded the objective and this exceeds the allowable frequency listed in Table 4.1 of the Listing Policy. 4. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 163726, Phosphorus	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343196

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
3 of 5 samples exceeded the water quality threshold for Phosphorus as P

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Phosphorus as P in this water body is 0.06 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163726, Phosphorus	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96653

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan field staff performing routine monitoring for the Surface Water Ambient Monitoring Program (SWAMP). Data were collected between September 2010 and November 2015. Concentrations in the raw data ranged from 0.029 to 0.123 mg/L. Six annual averages were computed, three of which exceeded the site specific objective in 2010, 2013 and 2015. Of note are the computed averages in 2010 and 2011 which are based on replicate data from one field visit in each instance.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for phosphorous in the Susan River above Willard Creek segment, as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 0.06 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637SUS003, which is located upstream of the confluence of the Susan River with Willard Creek slightly north of Korver Road and upstream of the Highway 36 bridge.

Temporal Representation:

Data were collected beginning in September 2010 when one field visit was made. One field visit was also made in June 2011. Between April 2012 and November 2015 the site was visited predominantly four times per calendar year between early Spring and late Fall.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 163726, Phosphorus	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23456

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2001 and1005. Concentrations of total phosphorus in 16 quarterly samples included three estimated values. Concentrations in the remainder of the samples ranged from 0.028 to 0.087 mg/L. Because of the estimated values in individual samples, the annual averages for 2001 and 2002 are estimates. Annual averages in the remaining 3 years (based on 3 to 4 samples per year) are j0.050, 0.054 and 0.066 mg/L. One of these averages exceeds the objective.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The applicable site-specific objective, from Lahontan Basin Plan Table 3-9, is an annual average total phosphorus concentration of 0.06 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Sixteen quarterly samples (3 to 4 per year) were taken between 2001 and 2005.

Environmental Conditions:

QAPP Information:

Sampling and analysis were done according to the SWAMP QAPP. However, in July 2009 an error was discovered in the QAPP related to holding times for total phosphorus samples that affects the validity of data for the Lahontan Region The holding time for samples that are not acid-preserved.should be 48 hours rather than 28 days as indicated in the QAPP. "Low level" phosphorus analyses, without acid preservation, are used in the Lahontan Region's SWAMP program. .

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163726, Phosphorus	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96657

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan field staff performing monitoring for the Surface Water Ambient Monitoring Program (SWAMP) Perennial Stream Survey. Data were collected on one occasion in August 2014. There was no detectable concentration in the sample and therefore did not exceed the site specific objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637PS0130, which is located 0.7 miles upstream of the confluence of the Susan River with Crazy Harry Gulch downstream of the Goumaz Campground.

Temporal Representation:

Data were collected on one occasion in August 2014.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 163726, Phosphorus	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343216

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed USFS Management Indicator Species - Streams data to determine beneficial use support and results are as follows:
1 of 1 samples exceeded the water quality threshold for Phosphorus as P

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Phosphorus as P in this water body is 0.06 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River (USFS) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	163728	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Total Dissolved Solids
Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the CWA section 303(d) List under section 4.2 of the Listing Policy. Under this section a single line of evidence is necessary to assess listing status. Six lines of evidence, five which evaluate data for the COLD beneficial use and one which evaluates data for the MUN beneficial use, are available in the administrative record to assess this pollutant. 0 of 16 samples exceed the water quality objective for the MUN beneficial use; 18 of 20 samples exceed the objective for the COLD beneficial use. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 18 of 20 samples evaluated for the COLD beneficial use exceeded the objective and this exceeds the allowable frequency listed in Table 4.2 of the Listing Policy. 4. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 163728, Total Dissolved Solids	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23457

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2001 and 2005. Concentrations in 16 quarterly samples (3-4 per year) ranged from 46 to 132 mg/L. Annual averages ranged from 77 to 125 mg/L. The site-specific objective was exceeded in 5 of 5 years.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site-specific objective from Lahontan Basin Plan Table 3-9 includes an annual average Total Dissolved Solids (TDS) concentration of 60 mg/L and a 90th percentile value of 75 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Sixteen quarterly samples (3 to 4 per year) were collected between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163728, Total Dissolved Solids	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96654

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan staff for the Surface Water Ambient Monitoring Program (SWAMP) RWB6 Monitoring program, and for a supplemental TMDL Integrated Report Special Study. The TMDL Special Study was developed by Lahontan Planning and SWAMP staff to provide additional data to the quarterly SWAMP monitoring. The purpose was to gain a better temporal understanding of levels of specific pollutants in the waterbody. To ensure the two datasets could be viably analyzed as one, the TMDL Special Study followed the same sampling protocol as SWAMP. Accordingly, the two datasets have been combined for this assessment to reflect the intended design and to best characterize conditions in the watershed. Data for the projects were collected between September 2010 and January 2017. Concentrations in the raw data ranged from 55 to 160 mg/L. Eight annual averages were computed, seven of which exceed the site specific objective. Only the annual average computed for 2011 did not exceed the water quality standard, but this averaged is based on one data point only. Also of note is the computed averages for 2010 and 2017 which are similarly based on one data point but which exceed the standard.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the TMDL Intergrated Report Special Study.

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for Total Dissolved Solids (TDS) in the Susan River (headwaters to Willard Creek), as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 60 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637SUS003, which is located upstream of the confluence of the Susan River with Willard Creek slightly north of Korver Road and upstream of the Highway 36 bridge.

Temporal Representation:

Data were collected beginning in September 2010. The site was again visited in June 2011. Between 2012 and 2016 the site was visited predominantly four times per calendar year. One site visit was made in January 2017.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 163728, Total Dissolved Solids	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23458

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The recommended MCL for total dissolved solids (TDS) is 500 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Sixteen quarterly samples (3 to 4 per year) were collected between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 163728, Total Dissolved Solids	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343376

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
2 of 3 samples exceeded the water quality threshold for Total Dissolved Solids

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Total Dissolved Solids in this water body is 60 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163728, Total Dissolved Solids	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343379

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed TMDL Intergrated Report Special Study data to determine beneficial use support and results are as follows:
1 of 1 samples exceeded the water quality threshold for Total Dissolved Solids

Data Reference:

WQ from the Total Maximum Daily Load for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Total Dissolved Solids in this water body is 60 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2017-02-15 and 2017-10-18

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163728, Total Dissolved Solids	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343388

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
3 of 3 samples exceeded the water quality threshold for Total Dissolved Solids

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Total Dissolved Solids in this water body is 60 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2017-11-07 and 2019-12-18

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	162260	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Alkalinity as CaCO3
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Seven lines of evidence are available in the administrative record to assess this pollutant, 5 that assess for COLD and 2 that assess for the WARM beneficial use. 0 of the 42 samples exceed the guideline for COLD and 0 of 20 samples exceed the guideline for WARM. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of the 42 samples exceed the guideline for COLD and 0 of 20 samples exceed the guideline for WARM and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 162260, Alkalinity as CaCO3	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98333

Pollutant:

Alkalinity as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Perennial Stream Surveys data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality standard for Alkalinity as CaCO3.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The National Recommended Water Quality Criteria for Alkalinity as CaCO3 for the protection of freshwater aquatic life is not less than 20000 ug/L. (National Recommended Water Quality Criteria 2016)

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637PS0130)

Temporal Representation:

The samples were collected between the dates of 2014-08-27 and 2014-08-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162260, Alkalinity as CaCO3	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98366

Pollutant:

Alkalinity as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for USFS Management Indicator Species - Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The National Recommended Water Quality Criteria for Alkalinity as CaCO3 for the protection of freshwater aquatic life is not less than 20000 ug/L. (National Recommended Water Quality Criteria 2016)

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2012-06-27 and 2012-06-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162260, Alkalinity as CaCO3	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

97101

Pollutant:

Alkalinity as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The National Recommended Water Quality Criteria for Alkalinity as CaCO3 for the protection of freshwater aquatic life is not less than 20000 ug/L. (National Recommended Water Quality Criteria 2016)

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2010-09-15 and 2015-11-17

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162260, Alkalinity as CaCO3	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

338003

Pollutant:

Alkalinity as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SSN077 (Susan River (USFS)).

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162260, Alkalinity as CaCO3	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

337877

Pollutant:

Alkalinity as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 19 samples exceeded the water quality threshold for Alkalinity as CaCO3.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162260, Alkalinity as CaCO3	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

338028

Pollutant:

Alkalinity as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SSN077 (Susan River (USFS)).

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162260, Alkalinity as CaCO3	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

337985

Pollutant:

Alkalinity as CaCO3

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The USEPA recommended alkalinity criterion continuous concentration (CCC) for the protection of aquatic life in freshwater is a minimum value of 20,000 ug/L (4-day average).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	170406	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Ammonia
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 170406, Ammonia	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98358

Pollutant:

Nitrogen, ammonia (Total Ammonia)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.

Objective/Criterion Reference:

Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637PS0130)

Temporal Representation:

The samples were collected between the dates of 2014-08-27 and 2014-08-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 170406, Ammonia	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

338298

Pollutant:

Ammonia (Unionized)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N, Unionized.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The un-ionized ammonia water quality objective to protect aquatic life in freshwater is temperature and pH dependent and is calculated according to the equation for the four-day criterion defined in Chapter 3 of The Water Quality Control Plan for the Lahontan Region.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2018-08-28 and 2018-08-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 170406, Ammonia	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

338257

Pollutant:

Ammonia (Unionized)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2018-08-28 and 2018-08-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 170406, Ammonia	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98288

Pollutant:

Nitrogen, ammonia (Total Ammonia)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637PS0130)

Temporal Representation:

The samples were collected between the dates of 2014-08-27 and 2014-08-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	162254	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Fluoride
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Five lines of evidence are available in the administrative record to assess this pollutant, two that assess data for the AG use, and three that assess for the MUN use. Zero of 11 samples exceed the guideline for AG and 0 of 31 samples exceed the objective for MUN. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Zero of 11 samples exceed the guideline for AG and 0 of 31 samples exceed the objective for MUN and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 162254, Fluoride	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

338598

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 8 samples exceeded the water quality threshold for Fluoride.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Waters designated as AGR shall not contain concentrations of chemical constituents in amounts that adversely affect the water for beneficial uses (i.e., agricultural purposes). (Water Quality Control Plan, Lahontan Region)

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water. These criteria were used to translate narrative water quality objectives for chemical constituents that prohibit chemicals in concentrations that would impair agricultural uses of water. A 1 mg/L criteria is the recommended maximum concentration of Fluoride in irrigation water.

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2016-07-12 and 2019-09-11

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162254, Fluoride	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

338584

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Fluoride.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Fluoride incorporated by reference in the Water Quality Control Plan, Lahontan Region is 2 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2017-11-07 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162254, Fluoride	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98708

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Fluoride incorporated by reference in the Water Quality Control Plan, Lahontan Region is 2 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2010-09-15 and 2015-11-17

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162254, Fluoride	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

338570

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2017-11-07 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162254, Fluoride	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

338600

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Fluoride incorporated by reference in the Water Quality Control Plan, Lahontan Region is 2 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2016-07-12 and 2019-09-11

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	170407	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Indicator Bacteria
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. Zero of the 33 samples exceed the objective. (Fecal coliform lines of evidence used in previous indicator bacteria decisions in the Lahontan Region have been removed from decisions, starting in the 2026 Integrated Report, because the Lahontan Region's fecal coliform objective was removed from the Basin Plan in 2024). Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Zero of the 33 samples exceed the objective, and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 170407, Indicator Bacteria	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

336864

Pollutant:

Escherichia coli (E. coli)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

STV

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and the results are as follows: 0 of the 10 samples exceeded the Statistical Threshold Value (STV) water quality threshold for E. coli. The STV is based on a 10% exceedance rate that is calculated monthly.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The bacteria water quality objective to protect the REC-1 beneficial use in waters other than Lake Thaoe, where the salinity is less than 1 parts per thousand 95 percent or more of the time applies a statistical threshold value to E. coli of 320 cfu/100 mL, not to be exceeded by more than 10 percent of samples within a calendar month (ISWEBE 2018).

Objective/Criterion Reference:

Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the days of 2016-01-26 and 2019-12-18 .

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 170407, Indicator Bacteria	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96936

Pollutant:

Escherichia coli (E. coli)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

STV

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan staff for the Surface Water Ambient Monitoring Program (SWAMP) RWB6 Monitoring program, and for a supplemental TMDL Integrated Report Special Study. The TMDL Special Study was developed by Lahontan Planning and SWAMP staff to provide additional data to the quarterly SWAMP monitoring. The purpose was to gain a better temporal understanding of levels of specific pollutants in the waterbody. To ensure the two datasets could be viably analyzed as one, the TMDL Special Study followed the same sampling protocol as SWAMP. Accordingly, the two datasets have been combined for this assessment to reflect the intended design and to best characterize conditions in the watershed. Water Board staff determined beneficial use support, and the results are as follows: 0 of 23 samples exceeded exceeded the Statistical Threshold Value (STV) water quality standard for E. coli. The STV is based on a 10% exceedance rate that is calculated monthly.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The bacteria water quality objective applicable to all waters, except Lake Tahoe, where the salinity is less than 10 parts per thousand (ppth) 95 percent or more of the time is a STATISTICAL THRESHOLD VALUE (STV) of 320 cfu/100 mL not to be exceeded more than 10 percent of the time (calculated monthly).

Objective/Criterion Reference:

Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site, station: 637SUS003

Temporal Representation:

The samples were collected between the days of 2011-22-6 and 2016-12-12 .

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	100878	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Iron
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Three lines of evidence which evaluate data for each of the COLD, WARM and MUN beneficial uses are available in the administrative record to assess this pollutant. 0 of 2 samples in each beneficial use assessment exceed the water quality criteria. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 2 samples in each of the beneficial use assessments exceeded the water quality criteria and this sample size is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. A minimum of 16 samples are needed to determine if a beneficial use is fully supported using table 3.1. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 100878, Iron	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98224

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality standard for Iron.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Lahontan Region?s Objective for Municipal and Domestic Supply uses of inland surface waters states that waters designated as MUN shall not contain concentrations of chemical constituents in excess of the maximum contaminant level (MCL) or secondary maximum contaminant level (SMCL). This is based upon drinking water standards specified in the following provisions of Title 22 of the California Code of Regulations which are incorporated by reference into the Water Quality Control Plan: Table 64431-A of Section 64431 (Inorganic Chemicals), Table 64431-B of Section 64431 (Fluoride), Table 64444-A of Section 64444 (Organic Chemicals), Table 64449-A of Section 64449 (Secondary Maximum Contaminant Levels-Ranges). The maximum contaminant level listed in Table 64449-A for Iron is 0.3 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2010-09-15 and 2011-06-22

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 100878, Iron	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98225

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations which are toxic to, or which produce detrimental physiological responses in, human, plant, animal, or aquatic life (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The Red Book states that based on field observations principally, a criterion of 1.0 mg/L iron for freshwater aquatic life is believed to be adequately protective.

Guideline Reference:

Quality Criteria for Water. USEPA Office of Water and Hazardous Materials. Washington, D.C

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2010-09-15 and 2011-06-22

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 100878, Iron	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98173

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The Red Book states that based on field observations principally, a criterion of 1.0 mg/L iron for freshwater aquatic life is believed to be adequately protective.

Guideline Reference:

Quality Criteria for Water. USEPA Office of Water and Hazardous Materials. Washington, D.C

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2010-09-15 and 2011-06-22

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	75828	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Nitrate/Nitrite (Nitrite + Nitrate as N)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. 3 lines of evidence are available in the administrative record to assess this pollutant. None of the 38 samples exceed the water quality criteria. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. None of the 38 samples exceeded the water quality criteria and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 75828, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98255

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for nitrate + nitrite (as N) that is incorporated by reference in the Water Quality Control Plan, Lahontan Region is 10.0 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637PS0130)

Temporal Representation:

The samples were collected between the dates of 2014-08-27 and 2014-08-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 75828, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23453

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2001 and 2005. Sixteen quarterly samples for nitrite plus nitrate included two estimated values and one sample below the detection level. Concentrations in the remainder of the samples ranged from 0.009 to 0.23 mg/L. The MCL was not exceeded.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for nitrite plus nitrate is 10 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Sixteen quarterly samples (3 to 4 per year) were collected between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 75828, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96873

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan staff for the Surface Water Ambient Monitoring Program (SWAMP) RWB6 Monitoring program, and for a supplemental TMDL Integrated Report Special Study. The TMDL Special Study was developed by Lahontan Planning and SWAMP staff to provide additional data to the quarterly SWAMP monitoring. The purpose was to gain a better temporal understanding of levels of specific pollutants in the waterbody. To ensure the two datasets could be viably analyzed as one, the TMDL Special Study followed the same sampling protocol as SWAMP. Accordingly, the two datasets have been combined for this assessment to reflect the intended design and to best characterize conditions in the watershed. Data for the projects were collected between September 2010 and November 2015 from the same monitoring station by Lahontan field personnel. Concentrations in the raw data ranged from 0.0187 to 0.359 mg/L. All data collected attained the water quality standard.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the TMDL Intergrated Report Special Study.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637SUS003, which is located upstream of the confluence of the Susan River with Willard Creek.

Temporal Representation:

Data were collected between September 2010 and November 2015 predominately once-per-quarter.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	100879	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Nitrogen, Nitrate
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. 0 of the 20 samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 20 samples exceeded the objective and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 100879, Nitrogen, Nitrate	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

26252

Pollutant:

Nitrate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Bureau of Land Management sampled the Susan River in June, July and August 2002. Concentrations of NO3-N in 5 samples ranged from 0.15 to 1.32 mg/L. The MCL was not exceeded.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for nitrate is 45 mg/L expressed "as nitrate," equivalent to 10 mg/L expressed "as N."

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Objective/Criterion Reference:

Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The USBLM sampled three stations, Susan River at Hobo Camp, Susan River at Devils Corral, and Susan River above Cheney Creek.

Temporal Representation:

Samples were collected on June 5, July 16, and August 19, 2002.

Environmental Conditions:

QAPP Information:

No quality assurance information was submitted with the USBLM data.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 100879, Nitrogen, Nitrate	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

97308

Pollutant:

Nitrogen, Nitrate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed TMDL Intergrated Report Special Study data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 15 samples exceeded the water quality standard for Nitrate as N.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the TMDL Intergrated Report Special Study.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for nitrate (NO3 as N) incorporated by reference in the Water Quality Control Plan, Lahontan Region is 10.0 mg/L (Water Quality Control Plan, Lahontan Region).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2014-11-18 and 2016-11-09

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	100880	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Nitrogen, Nitrite
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. 0 of the 19 samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 19 samples exceeded the objective and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 100880, Nitrogen, Nitrite	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

97301

Pollutant:

Nitrogen, Nitrite

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed TMDL Intergrated Report Special Study data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 19 samples exceeded the water quality standard for Nitrite as N.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the TMDL Intergrated Report Special Study.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan, Lahontan Basin, Objective for Municipal and Domestic Supply uses of inland surface waters states the following: waters shall not contain concentrations of inorganic chemicals in excess of the limits specified in California Code of Regulations, Title 22, Table 64431-A of section 64431 (Inorganic Chemicals). The maximum contaminant level listed in Table 64431-A for Nitrite as N is 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2014-11-18 and 2017-01-17

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program


DECISION ID	162255	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Oxygen, Dissolved
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Ten lines of evidence are available in the administrative record to assess this parameter: 6 which assess dissolved oxygen concentration data and 4 which assess dissolved oxygen percent saturation data. Three of 46 samples are below the objective for minimum dissolved oxygen concentration. One of 32 samples is below the objective for minimum dissolved oxygen percent saturation. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Three of 46 samples are below the objective for minimum dissolved oxygen concentration. One of 32 samples is below the objective for minimum dissolved oxygen percent saturation. This does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 162255, Oxygen, Dissolved	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

6918

Pollutant:

Dissolved oxygen saturation

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program. Percent saturation of dissolved oxygen was measured on 10/20/2004, 1/25/ 2005 and 7/20/2005. Percent saturation ranged from 104 to 105 percent. The objective was not violated.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The narrative objective in the Lahontan Basin Plan states that percent saturation shall not be depressed by more than 10 percent and minimum dissolved oxygen concentration shall not be less than 80 percent saturation.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Three measurements of percent saturation of dissolved oxygen were taken between October 2004 and July 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162255, Oxygen, Dissolved	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

6917

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2002 and 2005. Concentrations of dissolved oxygen in 12 quarterly samples ranged from 7.2 to 12.3 mg/L. Three samples were below the 8 mg/L minimum concentration.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The water quality objective, from Lahontan Basin Plan Table 3-6, is a one day minimum dissolved oxygen concentration of 8 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Twelve quarterly samples (3 to 4 per year) were taken between 2002 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162255, Oxygen, Dissolved	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

130156

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for USFS Management Indicator Species - Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Lahontan Region's water quality objective states that the dissolved oxygen concentration shall not be less than 80 percent of saturation.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2012-06-27 and 2012-06-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162255, Oxygen, Dissolved	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

130096

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 1 of 10 samples exceeded the water quality standard for Oxygen, Saturation.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Lahontan Region's water quality objective states that the dissolved oxygen concentration shall not be less than 80 percent of saturation.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2010-09-15 and 2013-07-09

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162255, Oxygen, Dissolved	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

130172

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality standard for Oxygen, Dissolved.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

For waters with the beneficial uses of COLD, COLD with SPWN, WARM, and WARM with SPWN, the minimum dissolved oxygen concentration shall not be less than that specified in Table 3-6. (Water Quality Control Plan, Lahontan Region)

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2010-09-15 and 2013-07-09

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162255, Oxygen, Dissolved	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

130060

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637PS0130)

Temporal Representation:

The samples were collected between the dates of 2014-08-27 and 2014-08-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162255, Oxygen, Dissolved	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

129991

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for USFS Management Indicator Species - Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2012-06-27 and 2012-06-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162255, Oxygen, Dissolved	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

339157

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 21 samples exceeded the water quality threshold for Oxygen, Dissolved.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2016-04-05 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162255, Oxygen, Dissolved	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

339317

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SSN077 (Susan River (USFS)).

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162255, Oxygen, Dissolved	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

339446

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 18 samples exceeded the water quality threshold for Oxygen, Saturation.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Lahontan Region's water quality objective states that the dissolved oxygen concentration shall not be less than 80 percent of saturation.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2016-04-06 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	78322	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Phosphate
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. No biological data are available for assessment of compliance with the water quality objective for biostimulatory substances and no numeric standard is available. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The dataset used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. The dataset consists of a single sample. 3. 0 of 1 samples exceed the water quality objective and this sample size is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. A minimum of 16 samples are needed to determine if a beneficial use is fully supported using table 3.1. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 78322, Phosphate	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23455

Pollutant:

Phosphate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program. A single sample for dissolved phosphate was collected on March 23, 2004. The concentration was 0.011 mg/L.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Lahontan Basin Plan does not include a site-specific objective (SSO) for phosphate in the Susan River. The narrative objective for biostimulatory substances states: "Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect the water for beneficial uses."

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

One sample was collected on March 23, 2004.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	162257	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Sodium
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Four lines of evidence are available in the administrative record to assess this pollutant, two that assess available data for the MUN use and two that the assess for the AG beneficial use. 0 of the 33 samples exceed the objective for MUN and 0 of 33 samples exceed the objective for AG. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of the 33 samples exceed the objective for MUN and 0 of 33 samples exceed the objective for AG and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 162257, Sodium	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

97129

Pollutant:

Sodium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 17 samples exceeded the water quality standard for Sodium.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water, including irrigation of various types of crops and stock watering. At or below the sodium threshold of 69 mg/L, agricultural uses of water should not be limited.

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2011-06-22 and 2015-11-17

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162257, Sodium	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

340239

Pollutant:

Sodium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 16 samples exceeded the water quality threshold for Sodium.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Per the Drinking Water Standards and Health Advisories (USEPA 2012), the health advisory for sodium for individuals on a sodium-restricted diet is 20 mg/l.

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162257, Sodium	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

97247

Pollutant:

Sodium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Per the Drinking Water Standards and Health Advisories (USEPA 2012), the health advisory for sodium for individuals on a sodium-restricted diet is 20 mg/l.

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2011-06-22 and 2015-11-17

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162257, Sodium	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

340254

Pollutant:

Sodium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Water Quality for Agriculture, published by the Food and Agriculture Organization of the United Nations in 1985, contains criteria protective of various agricultural uses of water, including irrigation of various types of crops and stock watering. At or below the sodium threshold of 69 mg/L, agricultural uses of water should not be limited.

Guideline Reference:

Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	170408	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Specific Conductivity
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Five lines of evidence are available in the administrative record to assess this pollutant. Zero of the 64 samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. ero of the 64 samples exceed the water quality objective, and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 170408, Specific Conductivity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

97438

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for USFS Management Indicator Species - Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's \Chemical Constituents\" objective. The California Secondary MCL for specific conductivity is 900 uS/cm."

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2012-06-27 and 2012-06-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 170408, Specific Conductivity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

340604

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's 'Chemical Constituents' objective. The California Secondary MCL for specific conductivity is 900 uS/cm.

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

The samples were collected at 1 monitoring site: 637SSN077 (Susan River (USFS)).

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 170408, Specific Conductivity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

97265

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2010-09-15 and 2015-11-17

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 170408, Specific Conductivity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

6919

Pollutant:

Specific Conductance

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2001 and 2005. Specific conductance in 16 quarterly field measurements ranged from 56 to 166 uS/cm. Specific conductance in one additional laboratory measurement was 158 uS/cm. The MCL was not exceeded.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for specific conductance is 900 microsiemens per centimeter (uS/cm).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Sixteen quarterly field measurements of specific conductance (3 to 4 per year) were taken between 2001 and 2005. One laboratory measurement was taken on September 9, 2003.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170408, Specific Conductivity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

26000

Pollutant:

Specific Conductance

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Bureau of Land Management sampled the Susan River in June, July and August 2002. Specific conductance in 5 samples ranged from 109 to 169 uS/cm. The MCL was not violated.

Data Reference:

Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Objective/Criterion Reference:

Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The USBLM sampled three stations, Susan River at Hobo Camp, Susan River at Devils Corral, and susan River above Cheney Creek.

Temporal Representation:

Samples were collected on June 5, July 16, and August 19, 2002.

Environmental Conditions:

QAPP Information:

No quality assurance information was submitted with the USBLM data.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170408, Specific Conductivity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98783

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637PS0130)

Temporal Representation:

The samples were collected between the dates of 2014-08-27 and 2014-08-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 170408, Specific Conductivity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

340644

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	162259	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Turbidity
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Seven lines of evidence are available in the administrative record to assess this pollutant, one that assesses available data for COLD, and six that assess data for MUN. Zero of 16 samples exceed the objective for COLD. and 5 of the 75 samples exceed the objective for MUN. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Zero of 16 samples exceed the objective for COLD. and 5 of the 75 samples exceed the objective for MUN and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 162259, Turbidity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

340878

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 1 of 16 samples exceeded the water quality threshold for Turbidity.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Water designated as MUN shall not contain concentrations of chemical constituents in excess of the maximum contaminant level (MCL) or secondary maximum contaminant level (SMCL) based upon drinking water standards specified in Title 22 of the California Code of Regulations. The Lahontan Basin Plan also has regionwide turbidity objective for other beneficial uses that states: Waters shall be free of changes in turbidity that cause nuisance or adversely affect the water for beneficial uses. Increases in turbidity shall not exceed natural levels by more than 10%.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

California Maximum Contaminant Levels (MCLs) apply to ambient surface waters under the Lahontan Basin Plan's 'Chemical Constituents' objective. The Secondary MCL for turbidity is 5 NTU. Calculation of a numeric objective for other beneficial uses requires comparison with upstream or other background data which may not be available as part of the data used for water quality assessment.

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2016-07-12 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162259, Turbidity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

340948

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

The samples were collected at 1 monitoring site: 637SSN077 (Susan River (USFS)).

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162259, Turbidity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96874

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan staff for the Surface Water Ambient Monitoring Program (SWAMP) RWB6 Monitoring program, and for a supplemental TMDL Integrated Report Special Study. The TMDL Special Study was developed by Lahontan Planning and SWAMP staff to provide additional data to the quarterly SWAMP monitoring. The purpose was to gain a better temporal understanding of levels of specific pollutants in the waterbody. To ensure the two datasets could be viably analyzed as one, the TMDL Special Study followed the same sampling protocol as SWAMP. Accordingly, the two datasets have been combined for this assessment to reflect the intended design and to best characterize conditions in the watershed. Data for the projects were collected between September 2010 and April 2017. Concentrations in the raw data ranged from 0.44 to 5.52 NTU. 42 data points were collected, 3 of which exceed the water quality objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the TMDL Intergrated Report Special Study.

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for turbidity is 5 NTU.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637SUS003, which is located upstream of the confluence of the Susan River with Willard Creek slightly north of Korver Road and upstream of the Highway 36 bridge.

Temporal Representation:

Data were collected beginning in September 2010. The site was again visited in June and December 2011. Between 2012 and 2016 the site was visited predominantly once every two months. The site was visited once per month between January and April 2017.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162259, Turbidity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23462

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2001 and 2004. One of 12 quarterly measurements of turbidity as NTU was below the detection level; the remainder ranged from 0.7 to 12 NTU. One sample exceeded the MCL.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for turbidity is 5 NTU.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Twelve quarterly turbidity measurements expressed as NTU (3 to 4 per year) were taken between 2001 and 2004.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162259, Turbidity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23469

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2004 and 2005. Two of four quarterly samples were below the detection level. Turbidity values in the other samples were 2.5 and 37 NTRU.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There are no state or federal standards or criteria for turbidity expressed as NTRU for the protection of human health.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Four quarterly turbidity measurements expressed as NTRU were taken in 2004 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162259, Turbidity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23461

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Lahontan Basin Plan's regionwide turbidity objective states:

"Waters shall be free of changes in turbidity that cause nuisance or adversely affect the water for beneficial uses. Increases in turbidity shall not exceed natural levels by more than 10 percent."

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Twelve quarterly turbidity measurements expressed as NTU (3 to 4 per year) were taken between 2001 and 2004.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162259, Turbidity	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23468

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Four quarterly turbidity measurements expressed as NTRU were taken in 2004 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	162256	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	pH
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

340063

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed USFS Management Indicator Species - Streams data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for pH. The objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality thresholds could not be made.

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Lahontan Basin Plan's regionwide objective for pH states: 'In fresh waters with designated beneficial uses of COLD or WARM, changes in normal ambient pH levels shall not exceed 0.5 pH units. For all other waters of the region, the pH shall not be depressed below 6.5 nor raised above 8.5 units. The Regional Board recognizes that some waters of the Region may have natural pH levels outside of the 6.5 to 8.5 range. Compliance with the pH objective for these waters will be determined on a case-by-case basis.'

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SSN077 (Susan River (USFS)).

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

97630

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed DFW_ABL_Monitoring data for Little Walker River to determine beneficial use support and results are as follows: 0 of 0 samples exceeded the water quality standard for pH. Although pH data does exist for this waterbody, the objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality standards could not be made

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Lahontan Basin Plan's regionwide objective for pH states: \In fresh waters with designated beneficial uses of COLD or WARM, changes in normal ambient pH levels shall not exceed 0.5 pH units. For all other waters of the region, the pH shall not be depressed below 6.5 nor raised above 8.5 units. The Regional Board recognizes that some waters of the Region may have natural pH levels outside of the 6.5 to 8.5 range. Compliance with the pH objective for these waters will be determined on a case-by-case basis.\""

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637PS0130)

Temporal Representation:

The samples were collected between the dates of 2014-08-27 and 2014-08-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

340108

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data for Susan River (Headwaters to Willard Crk) to determine beneficial use support and results are as follows: 0 of 20 samples exceeded the water quality threshold for pH. The objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality thresholds could not be made.

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

339940

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SSN077 (Susan River (USFS)).

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98188

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed RWB6 TMDL data for Lee Vining Creek to determine beneficial use support, and the results are as follows: 0 of 0 samples exceeded the water quality standard for pH. Although pH data does exist for this waterbody, the objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality standards could not be made

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2010-09-15 and 2015-11-17

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

26002

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Bureau of Land Management sampled the Susan River in June, July and August 2002. Five sampes had pH ranging from 7.6 to 8.9 units.

Data Reference:

Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The objective in the Lahontan Basin Plan states: "In fresh waters with designated beneficial uses of COLD or WARM, changes in normal ambient pH levels shall not exceed 0.5 pH units. For all other waters of the region, the pH shall not be depressed below 6.5 nor raised above 8.5 units.

The Regional Board recognizes that some waters of the Region may have natural pH levels outside of the 6.5 to 8.5 range. Compliance with the pH objective for these waters will be determined on a case-by-case basis."

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The USBLM sampled three stations, Susan River at Hobo Camp, Susan River at Devils Corral, and susan River above Cheney Creek.

Temporal Representation:

Samples were collected on June 5, July 16, and August 19, 2002.

Environmental Conditions:

QAPP Information:

No quality assurance information was submitted with the USBLM data.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

97643

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed DFW_ABL_Monitoring data for Little Walker River to determine beneficial use support and results are as follows:0 of 0 samples exceeded the water quality standard for pH. Although pH data does exist for this waterbody, the objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality standards could not be made

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637PS0130)

Temporal Representation:

The samples were collected between the dates of 2014-08-27 and 2014-08-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98373

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed RWB6_BACT_Monitoring data for West Fork Mojave River above Silverwood Lake to determine beneficial use support and results are as follows: 0 of 0 samples exceeded the water quality standard for pH. Although pH data does exist for this waterbody, the objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality standards could not be made

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for USFS Management Indicator Species - Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2012-06-27 and 2012-06-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98507

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed RWB6 TMDL data for Lee Vining Creek to determine beneficial use support and results are as follows: 0 of 0 samples exceeded the water quality standard for pH. Although pH data does exist for this waterbody, the objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality standards could not be made

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2010-09-15 and 2015-11-17

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

6920

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2001 and 2005. The range of pH in 15 quarterly field measurements was 7.5 to 8.8 units. One measurement was above 8.5. An additional laboratory measurement was 8.1 units.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Fifteen quarterly field measurements of pH (3 to 4 per year) were taken between 2001 and 2005. One laboratory measurement was taken on September 9, 2003.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

339950

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

340064

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SSN077 (Susan River (USFS)).

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98400

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed RWB6_BACT_Monitoring data for Deep Creek (below Lake) (San Bernardino County) to determine beneficial use support, and the results are as follows:0 of 0 samples exceeded the water quality standard for pH. Although pH data does exist for this waterbody, the objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality standards could not be made.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for USFS Management Indicator Species - Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2012-06-27 and 2012-06-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

97167

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed RWB6 TMDL data for Lee Vining Creek to determine beneficial use support and results are as follows:0 of 0 samples exceeded the water quality standard for pH. Although pH data does exist for this waterbody, the objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality standards could not be made

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2010-09-15 and 2015-11-17

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

97693

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed DFW_ABL_Monitoring data for By-Day Creek to determine beneficial use support and results are as follows: 0 of 0 samples exceeded the water quality standard for pH. Although pH data does exist for this waterbody, the objective for this pollutant requires background information that is currently unavailable, and therefore an assessment of water quality standards could not be made

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637PS0130)

Temporal Representation:

The samples were collected between the dates of 2014-08-27 and 2014-08-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

98397

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for USFS Management Indicator Species - Streams.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2012-06-27 and 2012-06-27

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 162256, pH	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

339623

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	171777	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Benthic Community Effects
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Benthic Community Effects are being considered for placement on the CWA section 303(d) List under sections 3.9 of the Listing Policy. Under section 3.9, additional lines of evidence (LOEs) associating the Benthic Community Effects decision with a water or sediment concentration of pollutants other than benthic-macroinvertebrate bioassessment or habitat assessment LOEs are necessary to place a water body on the 303(d) List for Benthic Community Effects. Four lines of evidence evaluating benthic-macroinvertebrate bioassessment data are available in the administrative record to assess this indicator. Three of five benthic-macroinvertebrate samples exceed the California Stream Condition Index (CSCI) impairment threshold. Additionally, there are associated pollutant impairments on the waterbody (including but not necessarily limited to boron, chloride, phosphorus, sulfates, and total nitrogen). Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for placing Benthic Community Effects in this waterbody segment on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 3 of 5 benthic-macroinvertebrate bioassessment samples had CSCI scores below 0.79. Therefore, this water body is exceeding the water quality threshold for the protection of the COLD beneficial use. 4. Pursuant to section 3.9 of the Listing Policy, the water segment has associated pollutant(s) samples that exceed water quality objectives. 5. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

352908

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 637SUS003 to determine beneficial use support and the results are as follows: 0 of 1 samples exceeded the water quality standard. CSCI scores were from 1.0656272447 to 1.0656272447 .

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rhen, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.)

Guideline Reference:

Bioassessment in complex environments: designing an index for consistent meaning in different settings

Spatial Representation:

The samples were collected at 1 monitoring site: 637SUS003 (Susan River, above confluence w/ Willard Cr).

Temporal Representation:

Samples were collected from 2018-08-28 to 2018-08-28.

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

352906

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 637SSN077 to determine beneficial use support and the results are as follows: 2 of 2 samples exceeded the water quality standard. CSCI scores were from 0.470519677 to 0.60345364 .

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Bioassessment in complex environments: designing an index for consistent meaning in different settings

Spatial Representation:

The samples were collected at 1 monitoring site: 637SSN077 (Susan River (USFS)).

Temporal Representation:

Samples were collected from 2012-06-27 to 2019-07-09.

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23459

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The applicable site-specific objective, from Lahontan Basin Plan Table 3-9, includes an annual average total nitrogen concentration of 0.20 mg/L and a 90th percentile value of 0.30 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Sixteen quarterly samples each (3 to 4 per year) were taken for total Kjeldahl nitrogen and nitrite plus nitrate between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96379

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

The site had a CSCI score of 1.113983365. Therefore, this site is not exceeding the water quality objective for the aquatic life beneficial use.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Bioassessment in complex environments: designing an index for consistent meaning in different settings

Spatial Representation:

Collected at site 637PS0130

Temporal Representation:

Collected on 8/27/2014

Environmental Conditions:

QAPP Information:

QAPP for SWAMP Perennial Stream Surveys

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96508

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

The CSCI score from this water body was 0.426151688, which does not meet the water quality objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for USFS Management Indicator Species - Streams.

SWAMP Data:

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Bioassessment in complex environments: designing an index for consistent meaning in different settings

Spatial Representation:

Sample collected from station 637SSN077

Temporal Representation:

Sample collected on 6/27/2012

Environmental Conditions:

QAPP Information:

QAPP for USFS Management Indicator Species

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

342710

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
3 of 4 samples exceeded the water quality threshold for Boron

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Boron in this water body is 0.01 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2016-04-05 and 2019-12-18

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96627

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan field staff performing routine monitoring for the Surface Water Ambient Monitoring Program (SWAMP). Data were collected between September 2010 and November 2015. Concentrations in the raw data ranged from 0.0013 to 0.461. Six annual averages were computed, two of which exceeded the site specific objective in 2014 and 2015. Of note are the computed averages in 2010 and 2011 which are based on one data point only, in comparison to the other years which all used a minimum of three raw data points in their calculations.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for boron in the Susan River above Willard Creek segment, as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 0.01 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637SUS003, which is located upstream of the confluence of the Susan River with Willard Creek slightly north of Korver Road and upstream of the Highway 36 bridge.

Temporal Representation:

Data were collected beginning in September 2010 when one field visit was made. The site was again visited in June 2011. The site was visited predominantly four times per calendar year between 2012 and 2015 between early Spring and late Fall.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

6914

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site-specific objective from Lahontan Basin Plan Table 3-9 includes an annual average chloride concentration of 0.7 mg/L and a 90th percentile value of 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Sixteen quarterly samples (3 to 4 per year) were collected between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

342740

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
3 of 5 samples exceeded the water quality threshold for Chloride

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Chloride in this water body is 0.7 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2021-06-24

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96628

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for chloride in Susan River above Willard Creek segment, as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 0.7 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637SUS003, which is located upstream of the confluence of the Susan River with Willard Creek slightly north of Korver Road and upstream of the Highway 36 bridge.

Temporal Representation:

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96659

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for chloride in the Susan River above Willard Creek segment, as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 0.7 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637PS0130, which is located 0.7 miles upstream of the confluence of the Susan River with Crazy Harry Gulch downstream of the Goumaz Campground.

Temporal Representation:

Data were collected on one occasion in August 2014.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

342752

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Chloride in this water body is 0.7 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River (USFS) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96657

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan field staff performing monitoring for the Surface Water Ambient Monitoring Program (SWAMP) Perennial Stream Survey. Data were collected on one occasion in August 2014. There was no detectable concentration in the sample and therefore did not exceed the site specific objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637PS0130, which is located 0.7 miles upstream of the confluence of the Susan River with Crazy Harry Gulch downstream of the Goumaz Campground.

Temporal Representation:

Data were collected on one occasion in August 2014.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343216

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Phosphorus as P in this water body is 0.06 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River (USFS) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96653

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan field staff performing routine monitoring for the Surface Water Ambient Monitoring Program (SWAMP). Data were collected between September 2010 and November 2015. Concentrations in the raw data ranged from 0.029 to 0.123 mg/L. Six annual averages were computed, three of which exceeded the site specific objective in 2010, 2013 and 2015. Of note are the computed averages in 2010 and 2011 which are based on replicate data from one field visit in each instance.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637SUS003, which is located upstream of the confluence of the Susan River with Willard Creek slightly north of Korver Road and upstream of the Highway 36 bridge.

Temporal Representation:

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23456

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The applicable site-specific objective, from Lahontan Basin Plan Table 3-9, is an annual average total phosphorus concentration of 0.06 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Sixteen quarterly samples (3 to 4 per year) were taken between 2001 and 2005.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343196

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
3 of 5 samples exceeded the water quality threshold for Phosphorus as P

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Phosphorus as P in this water body is 0.06 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343332

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Sulfate in this water body is 1 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River (USFS) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343302

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
2 of 4 samples exceeded the water quality threshold for Sulfate

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Sulfate in this water body is 1 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2019-12-18

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96656

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan field staff performing monitoring for the Surface Water Ambient Monitoring Program (SWAMP) Perennial Stream Survey. Data were collected on one occasion in August 2014. The reported concentration was 0.71 mg/L, which does not exceed the site specific objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for sulfates in the Susan River above Willard Creek segment, as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637PS0130, which is located 0.7 miles upstream of the confluence of the Susan River with Crazy Harry Gulch downstream of the Goumaz Campground.

Temporal Representation:

Data were collected on one occasion in August 2014.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96630

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan field staff performing routine monitoring for the Surface Water Ambient Monitoring Program (SWAMP). Data were collected between September 2010 and November 2015. Concentrations in the raw data ranged from non-detect to 2.73 mg/L. Six annual averages were computed, two of which exceeded the site specific objective in 2013 and 2015. Of note is the computed average in 2010 which is based on replicate data from one field visit. Furthermore, averages computed for 2013 and 2015 may have been skewed by high results of 2.75 and 2.73 mg/L, both of which were collected in February of the corresponding year.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for sulfates in the Susan River above Willard Creek segment, as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637SUS003, which is located upstream of the confluence of the Susan River with Willard Creek slightly north of Korver Road and upstream of the Highway 36 bridge.

Temporal Representation:

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 171777, Benthic Community Effects	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

26253

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Bureau of Land Management sampled the Susan River in June, July and August 2002. Samples were not collected for total nitrogen. Concentrations of NO3-N in 5 samples ranged from 0.15 to 1.32 mg/L. The "annual average" calculated from these samples was 0.22 mg/L, slightly exceeding the objective.

Data Reference:

Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The site-specific water quality objective for total nitrogen is an annual average of 0.2 mg/L and a 90th percentile value of 0.3 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Objective/Criterion Reference:

Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The USBLM sampled three stations, Susan River at Hobo Camp, Susan River at Devils Corral, and Susan River above Cheney Creek.

Temporal Representation:

Samples were collected on June 5, July 16, and August 19, 2002.

Environmental Conditions:

QAPP Information:

No quality assurance information was submitted with the USBLM data.

QAPP Information Reference(s):


DECISION ID	163724	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Boron
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. Five of the 10 samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Five of the 10 samples exceed the water quality objective and this exceeds the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 163724, Boron	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96627

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan field staff performing routine monitoring for the Surface Water Ambient Monitoring Program (SWAMP). Data were collected between September 2010 and November 2015. Concentrations in the raw data ranged from 0.0013 to 0.461. Six annual averages were computed, two of which exceeded the site specific objective in 2014 and 2015. Of note are the computed averages in 2010 and 2011 which are based on one data point only, in comparison to the other years which all used a minimum of three raw data points in their calculations.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for boron in the Susan River above Willard Creek segment, as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 0.01 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637SUS003, which is located upstream of the confluence of the Susan River with Willard Creek slightly north of Korver Road and upstream of the Highway 36 bridge.

Temporal Representation:

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 163724, Boron	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

342710

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
3 of 4 samples exceeded the water quality threshold for Boron

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Boron in this water body is 0.01 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2016-04-05 and 2019-12-18

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	163727	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Sulfates
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Five lines of evidence are available in the administrative record to assess this pollutant. 5 of the 14 samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 5 of 14 samples exceed the water quality objective and this exceeds the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 163727, Sulfates	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343311

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
0 of 2 samples exceeded the water quality threshold for Sulfate

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Sulfate in this water body is 1 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2017-11-07 and 2021-09-28

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163727, Sulfates	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343332

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Benthic, Field, Habitat, WQ from the USFS Management Indicator Species for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Sulfate in this water body is 1 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River (USFS) (637SSN077)

Temporal Representation:

The samples were collected between the dates of 2019-07-09 and 2019-07-09

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163727, Sulfates	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96630

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan field staff performing routine monitoring for the Surface Water Ambient Monitoring Program (SWAMP). Data were collected between September 2010 and November 2015. Concentrations in the raw data ranged from non-detect to 2.73 mg/L. Six annual averages were computed, two of which exceeded the site specific objective in 2013 and 2015. Of note is the computed average in 2010 which is based on replicate data from one field visit. Furthermore, averages computed for 2013 and 2015 may have been skewed by high results of 2.75 and 2.73 mg/L, both of which were collected in February of the corresponding year.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP RWB6 Monitoring (tissue and water).

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for sulfates in the Susan River above Willard Creek segment, as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637SUS003, which is located upstream of the confluence of the Susan River with Willard Creek slightly north of Korver Road and upstream of the Highway 36 bridge.

Temporal Representation:

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 163727, Sulfates	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

96656

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data were collected by Lahontan field staff performing monitoring for the Surface Water Ambient Monitoring Program (SWAMP) Perennial Stream Survey. Data were collected on one occasion in August 2014. The reported concentration was 0.71 mg/L, which does not exceed the site specific objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Perennial Stream Surveys.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The site specific objective for sulfates in the Susan River above Willard Creek segment, as referenced in the Lahontan Basin Plan table 3-9, is an annual average concentration not to exceed 1.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data were collected from one site, 637PS0130, which is located 0.7 miles upstream of the confluence of the Susan River with Crazy Harry Gulch downstream of the Goumaz Campground.

Temporal Representation:

Data were collected on one occasion in August 2014.

Environmental Conditions:

The Susan River is an internally drained river in eastern Lassen County with its headwaters near Lassen Volcanic National Park and its terminus in Honey Lake in the Great Basin. The headwaters reach is characterized by predominantly forested lands, and Lassen Co. is historically known for its industrial timber harvest.

QAPP Information:

Data were collected in accordance with the SWAMP QAPP.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 163727, Sulfates	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

343302

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP RWB6 Monitoring data to determine beneficial use support and results are as follows:
2 of 4 samples exceeded the water quality threshold for Sulfate

Data Reference:

Benthic, Field, Habitat, Tissue, Toxicity, WQ from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 6

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Sulfate in this water body is 1 (mg/L), (as a Mean).

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: Susan River, above confluence w/ Willard Cr (637SUS003)

Temporal Representation:

The samples were collected between the dates of 2016-02-11 and 2019-12-18

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	75988	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Sediment
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. 0 of 17 samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used does not satisfy the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 17 samples exceeded the objective and this sample size is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. A minimum of 26 samples are needed to determine if a beneficial use is fully supported using table 3.2. 4. Pursuant to SECTION 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 75988, Sediment	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

26009

Pollutant:

Sediment

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Bureau of Land Management sampled the Susan River in June, July and August 2002. Suspended sediment concentrations in 5 samples ranged from 5.4 to 24.3 mg/L.

Data Reference:

Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The objective from the Lahontan Basin Plan states: "The suspended sediment load and suspended sediment discharge rate of surface waters shall not be altered in such a manner as to cause nuisance or adversely affect the water for beneficial uses."

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The USBLM sampled three stations, Susan River at Hobo Camp, Susan River at Devils Corral, and Susan River above Cheney Creek.

Temporal Representation:

Samples were collected on June 5, July 16, and August 19, 2002.

Environmental Conditions:

QAPP Information:

No quality assurance information was submitted with the USBLM data.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 75988, Sediment	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23460

Pollutant:

Sediment

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2002 and 2005. One of twelve suspended sediment samples was below the detection level. Concentrations in the rest of the samples ranged from 2 to 46 mg/L. Instantaneous discharge flows for the suspended sediment sampling dates ranged from 5.8 to 103 cubic feet per second. Eight suspended sediment load calculations were done; one of these was below detection level. The remainder ranged from 0.14 to 9.8 tons per day.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Twelve quarterly samples (2 to 4 per year) were taken between 2002 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):


DECISION ID	75935	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Temperature, water
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollution

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. 0 of 21 samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used does not satisfy the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 21 samples exceeded the objective and this sample size is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. A minimum of 26 samples are needed to determine if a beneficial use is fully supported using table 3.2. 4. Pursuant to SECTION 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 75935, Temperature, water	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

6916

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2001 and 2005. Temperatures in 16 quarterly field measurements ranged from 2 to 21 degrees Celsius.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The applicable language from the Lahontan Basin Plan's water quality objective for temperature states: "The natural receiving water temperature of all waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such an alteration in temperature does not adversely affect the water for beneficial uses.

For waters designated WARM, water temperature shall not be altered by more than five degrees Fahrenheit ... above or below the natural temperature. For waters designated COLD, the temperature shall not be altered."

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Sixteen quarterly temperature measurements (3 to 4 per year) were taken between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 75935, Temperature, water	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

26003

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Bureau of Land Management sampled the Susan River in June, July and August 2002. Water temperatures in 5 samples ranged from 13.2 to 22 degrees Celsius.

Data Reference:

Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The USBLM sampled three stations, Susan River at Hobo Camp, Susan River at Devils Corral, and Susan River above Cheney Creek.

Temporal Representation:

Samples were collected on June 5, July 16, and August 19, 2002.

Environmental Conditions:

QAPP Information:

No quality assurance information was submitted with the USBLM data.

QAPP Information Reference(s):


DECISION ID	75466	Region 6
Susan River (Headwaters to Willard Crk)

Pollutant:	Total Kjeldahl Nitrogen (TKN)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. 0 of 16 samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 16 samples exceeded the objective and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 75466, Total Kjeldahl Nitrogen (TKN)	Region 6
Susan River (Headwaters to Willard Crk)

LOE ID:

23452

Pollutant:

Total Kjeldahl Nitrogen (TKN)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

The U.S. Geological Survey sampled the Susan River under the Region 6 SWAMP program between 2001 and1005. Concentrations of TKN in 16 quarterly samples ranged from
0.1 to 0.64 mg/L.

Data Reference:

2007. SWAMP Data for the Susan River

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

The Lahontan Basin Plan does not include a site-specific objective (SSO) for total Kjeldahl nitrogen (TKN) in the Susan River. The narrative objective for biostimulatory substances states: "Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect the water for beneficial uses."

Objective/Criterion Reference:

Water Quality Control Plan for the Lahontan Region (as amended)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One station (Susan River above confluence with Willard Creek) was sampled.

Temporal Representation:

Sixteen quarterly samples (3 to 4 per year) were taken between 2001 and 2005.

Environmental Conditions:

QAPP Information:

The data meet the quality assurance requirements of the SWAMP QAPP.

QAPP Information Reference(s):