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

Supporting Information

Regional Board 6 - Lahontan Region

Water Body Name:	Prosser Creek
Water Body ID:	CAR6352003020170823028547
Water Body Type:	River & Stream


DECISION ID	170258	Region 6
Prosser Creek

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 170258, Ammonia	Region 6
Prosser Creek

LOE ID:

338187

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 Truckee River Watershed Council data for Prosser Creek to determine beneficial use support and results are as follows: 0 of 5 samples exceeded the water quality threshold for Ammonia as N, Unionized.

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-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: MTRPROS01 (Prosser Creek below dam).

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 170258, Ammonia	Region 6
Prosser Creek

LOE ID:

97386

Pollutant:

Nitrogen, ammonia (Total Ammonia)

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 Truckee River Watershed Council data for Prosser Creek to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality standard for Ammonia as N.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the Truckee River Watershed Council.

SWAMP Data:

Non-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) (MTRPROS01)

Temporal Representation:

The samples were collected between the dates of 2015-05-16 and 2016-09-24

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.


DECISION ID	170932	Region 6
Prosser Creek

Pollutant:	Benthic Community Effects
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:	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. One line of evidence evaluating benthic-macroinvertebrate bioassessment data is available in the administrative record to assess this indicator. Two of two benthic-macroinvertebrate samples exceed the California Stream Condition Index (CSCI) impairment threshold. However, there are no LOEs associating the Benthic Community Effects decision with a water or sediment concentration indicating non-attainment of an aquatic life beneficial use. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against 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. Two of two benthic-macroinvertebrate bioassessment samples had CSCI scores below 0.79. The available information is insufficient to determine whether the waterbody/pollutant combination should be placed on the 303(d) List of impaired waters at this time. A minimum of 2 samples is needed to determine impairment 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:

Line of Evidence (LOE) for Decision ID 170932, Benthic Community Effects	Region 6
Prosser Creek

LOE ID:

352929

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 MTRPRBD to determine beneficial use support and the results are as follows: 2 of 2 samples exceeded the water quality standard. CSCI scores were from 0.61541179837 to 0.67801033413 .

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council 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. (Lahontan Basin Plan)

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: MTRPRBD (Prosser Creek half mile below Prosser Dam).

Temporal Representation:

Samples were collected from 2014-07-09 to 2018-06-20.

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.


DECISION ID	103264	Region 6
Prosser Creek

Pollutant:	Indicator Bacteria
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 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Two lines of evidence, one evaluating fecal coliform log-mean data and one evaluating fecal coliform Statistical Threshold Value (STV) data are available in the administrative record to assess this pollutant. 0 of 2 samples in either evaluation 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 2 samples in either the log-mean or STV evaluation 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 per pollutant fraction assessed 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 103264, Indicator Bacteria	Region 6
Prosser Creek

LOE ID:

129244

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Truckee River Watershed Council data for Prosser Creek to determine beneficial use support and the results are as follows: 0 of the 2 samples exceeded the logmean water quality standard for Coliform, Fecal. This is a 30-day rolling logmean that is calculated daily.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the Truckee River Watershed Council.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Waters shall not contain concentrations of coliform organisms attributable to anthropogenic sources, including human and livestock wastes. The fecal coliform concentration during any 30-day period shall not exceed a log mean of 20/100 ml. (Lahontan Region Basin Plan)

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), station(s): MTRPROS01

Temporal Representation:

The samples were collected between the days of 2015-05-16 and 2016-05-14 .

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 103264, Indicator Bacteria	Region 6
Prosser Creek

LOE ID:

129176

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Truckee River Watershed Council data for Prosser Creek to determine beneficial use support and the results are as follows: 0 of the 2 samples exceeded the water quality standard for Coliform, Fecal. The water quality standard 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 Truckee River Watershed Council.

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(s), station(s): MTRPROS01

Temporal Representation:

The samples were collected between the days of 2015-05-16 and 2016-05-14 .

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.


DECISION ID	162610	Region 6
Prosser Creek

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)(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 162610, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
Prosser Creek

LOE ID:

97425

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:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Truckee River Watershed Council data for Prosser Creek to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality standard for Nitrate + Nitrite as N.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the Truckee River Watershed Council.

SWAMP Data:

Non-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) (MTRPROS01)

Temporal Representation:

The samples were collected between the dates of 2015-05-16 and 2016-09-24

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 162610, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
Prosser Creek

LOE ID:

97613

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:

Water Board staff assessed SWAMP Monitoring data for Prosser Creek to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality standard for Nitrate + Nitrite as N.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Monitoring.

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) (635340500)

Temporal Representation:

The samples were collected between the dates of 2012-09-15 and 2012-09-15

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 162610, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
Prosser Creek

LOE ID:

338812

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:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Truckee River Watershed Council data for Prosser Creek to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Nitrate + Nitrite as N.

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council 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: MTRPROS02 (Prosser at Highway 89).

Temporal Representation:

The samples were collected between the dates of 2017-09-22 and 2017-09-22

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 162610, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 6
Prosser Creek

LOE ID:

338803

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:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Truckee River Watershed Council data for Prosser Creek to determine beneficial use support and results are as follows: 0 of 7 samples exceeded the water quality threshold for Nitrate + Nitrite as N.

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council 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: MTRPROS01 (Prosser Creek below dam).

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.


DECISION ID	163793	Region 6
Prosser Creek

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. Five lines of evidence are available in the administrative record to assess this parameter: 3which assess dissolved oxygen concentration data and 2 which assess dissolved oxygen percent saturation data. Two of 92 samples are below the objective for minimum dissolved oxygen concentration. Zero of 20 samples are 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. Two of 92 samples are below the objective for minimum dissolved oxygen concentration. Zero of 20 samples are 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 163793, Oxygen, Dissolved	Region 6
Prosser Creek

LOE ID:

130006

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 Truckee River Watershed Council data for Prosser Creek to determine beneficial use support and results are as follows: 0 of 48 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 Truckee River Watershed Council.

SWAMP Data:

Non-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 2 monitoring site(s) (MTRPROS01, MTRPROS02)

Temporal Representation:

The samples were collected between the dates of 2010-09-24 and 2016-09-24

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 163793, Oxygen, Dissolved	Region 6
Prosser Creek

LOE ID:

351225

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 Truckee River Watershed Council data to determine beneficial use support and results are as follows:
0 of 9 samples fell below the minimum water quality threshold for Oxygen, Dissolved

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Oxygen, Dissolved in this water body is 80 (%), (as a Min).

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: Prosser at Highway 89 (MTRPROS02)

Temporal Representation:

The samples were collected between the dates of 2018-06-23 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 163793, Oxygen, Dissolved	Region 6
Prosser Creek

LOE ID:

351200

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 Truckee River Watershed Council data to determine beneficial use support and results are as follows:
0 of 11 samples fell below the minimum water quality threshold for Oxygen, Dissolved

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Oxygen, Dissolved in this water body is 80 (%), (as a Min).

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: Prosser Creek below dam (MTRPROS01)

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 163793, Oxygen, Dissolved	Region 6
Prosser Creek

LOE ID:

351321

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 Truckee River Watershed Council data to determine beneficial use support and results are as follows:
1 of 22 samples fell below the minimum water quality threshold for Oxygen, Dissolved

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Oxygen, Dissolved in this water body is 7 (mg/L), (as a Min).

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: Prosser at Highway 89 (MTRPROS02)

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 163793, Oxygen, Dissolved	Region 6
Prosser Creek

LOE ID:

351314

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 Truckee River Watershed Council for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Oxygen, Dissolved in this water body is 7 (mg/L), (as a Min).

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: Prosser Creek below dam (MTRPROS01)

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.


DECISION ID	169004	Region 6
Prosser Creek

Pollutant:	Phosphorus
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 169004, Phosphorus	Region 6
Prosser Creek

LOE ID:

96924

Pollutant:

Phosphorus

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:

The water quality data for Phosphorus were collected by the Truckee River Watershed Council and consist of data collected during three separate sampling events, twice in 2015 and once in 2016. This resulted in two mean of monthly mean values (0.033 and 0.047 mg/L), none of which exceeded the objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the Truckee River Watershed Council.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The site specific objective for Phosphorus can be found in the Water Quality Control Plan for the Lahontan Basin in Table 3-11 and is 0.05 mg/L for the Truckee River below Prosser Creek. The objective is applied as the mean of monthly means calculated on an annual basis. Prosser Creek is a tributary to the Truckee River.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The data were collected at one sampling location at Prosser Creek below the dam.

Temporal Representation:

The data were collected on three separate occasions, twice in 2015 and once in 2016.

Environmental Conditions:

QAPP Information:

The data were collected in accordance with the Quality Assurance Project Plan for Truckee River Monitoring Plan.

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 169004, Phosphorus	Region 6
Prosser Creek

LOE ID:

347929

Pollutant:

Phosphorus

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 Truckee River Watershed Council data to determine beneficial use support and results are as follows:
0 of 1 samples exceeded the water quality threshold for Phosphorus as P

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council 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 0.05 (mg/L), (as a MOMMPR).

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: Prosser at Highway 89 (MTRPROS02)

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 169004, Phosphorus	Region 6
Prosser Creek

LOE ID:

347917

Pollutant:

Phosphorus

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 Truckee River Watershed Council data to determine beneficial use support and results are as follows:
1 of 4 samples exceeded the water quality threshold for Phosphorus as P

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council 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 0.05 (mg/L), (as a MOMMPR).

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: Prosser Creek below dam (MTRPROS01)

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.


DECISION ID	170134	Region 6
Prosser Creek

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)(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 170134, Total Kjeldahl Nitrogen (TKN)	Region 6
Prosser Creek

LOE ID:

348021

Pollutant:

Total Kjeldahl Nitrogen (TKN)

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 Truckee River Watershed Council data to determine beneficial use support and results are as follows:
0 of 4 samples exceeded the water quality threshold for Nitrogen, Total Kjeldahl

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Nitrogen, Total Kjeldahl in this water body is 0.26 (mg/L), (as a MOMMPR).

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: Prosser Creek below dam (MTRPROS01)

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 170134, Total Kjeldahl Nitrogen (TKN)	Region 6
Prosser Creek

LOE ID:

96923

Pollutant:

Total Kjeldahl Nitrogen (TKN)

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:

The water quality data for Total Kjeldahl Nitrogen were collected by the Truckee River Watershed Council and consist of data collected during three separate sampling events, twice in 2015 and once in 2016. This resulted in two mean of monthly mean values (0.24 and 0.38 mg/L), one of which exceeded the objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the Truckee River Watershed Council.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The site specific objective for Total Kjeldahl Nitrogen can be found in the Water Quality Control Plan for the Lahontan Basin in Table 3-11 and is 0.26 mg/L for the Truckee River below Prosser Creek. This objective is applied as the mean of monthly means calculated on an annual basis. Prosser Creek is a tributary to the Truckee River.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The data were collected at one sampling location at Prosser Creek below the dam.

Temporal Representation:

The data were collected on three separate occasions, twice in 2015 and once in 2016.

Environmental Conditions:

QAPP Information:

The data were collected in accordance with the Quality Assurance Project Plan for Truckee River Monitoring Plan.

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 170134, Total Kjeldahl Nitrogen (TKN)	Region 6
Prosser Creek

LOE ID:

348026

Pollutant:

Total Kjeldahl Nitrogen (TKN)

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 Truckee River Watershed Council data to determine beneficial use support and results are as follows:
0 of 1 samples exceeded the water quality threshold for Nitrogen, Total Kjeldahl

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Nitrogen, Total Kjeldahl in this water body is 0.26 (mg/L), (as a MOMMPR).

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: Prosser at Highway 89 (MTRPROS02)

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.


DECISION ID	163794	Region 6
Prosser Creek

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. Three lines of evidence, two which assess the available data for the COLD beneficial use and one which assesses the available data for the MUN beneficial use are available in the administrative record to assess this pollutant. Zero of eight samples exceed the applicable water quality objective for the COLD beneficial use assessment; three of 49 samples exceed the objective for the MUN beneficial use assessment. 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 eight samples exceed the applicable water quality objective for the COLD beneficial use assessment; three of 49 samples exceed the objective for the MUN beneficial use assessment, 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 163794, Turbidity	Region 6
Prosser Creek

LOE ID:

343455

Pollutant:

Turbidity

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 Truckee River Watershed Council data to determine beneficial use support and results are as follows:
0 of 4 samples exceeded the water quality threshold for Turbidity

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Turbidity in this water body is 3 (NTU), (as a MOMM).

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: Prosser Creek below dam (MTRPROS01)

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 163794, Turbidity	Region 6
Prosser Creek

LOE ID:

97400

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 Truckee River Watershed Council data for Prosser Creek to determine beneficial use support and results are as follows: 3 of 49 samples exceeded the water quality standard for Turbidity.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the Truckee River Watershed Council.

SWAMP Data:

Non-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 2 monitoring site(s) (MTRPROS01, MTRPROS02)

Temporal Representation:

The samples were collected between the dates of 2010-09-24 and 2016-09-24

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 163794, Turbidity	Region 6
Prosser Creek

LOE ID:

343429

Pollutant:

Turbidity

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 Truckee River Watershed Council data to determine beneficial use support and results are as follows:
0 of 4 samples exceeded the water quality threshold for Turbidity

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan objective for Turbidity in this water body is 3 (NTU), (as a MOMM).

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: Prosser at Highway 89 (MTRPROS02)

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.


DECISION ID	162611	Region 6
Prosser Creek

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:

Line of Evidence (LOE) for Decision ID 162611, pH	Region 6
Prosser Creek

LOE ID:

129554

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:

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 Truckee River Watershed Council.

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 2 monitoring site(s) (MTRPROS01, MTRPROS02)

Temporal Representation:

The samples were collected between the dates of 2010-09-24 and 2016-09-24

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 162611, pH	Region 6
Prosser Creek

LOE ID:

129835

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 the Truckee River Watershed Council.

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 2 monitoring site(s) (MTRPROS01, MTRPROS02)

Temporal Representation:

The samples were collected between the dates of 2010-09-24 and 2016-09-24

Environmental Conditions:

QAPP Information:

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 162611, pH	Region 6
Prosser Creek

LOE ID:

339907

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 Truckee River Watershed Council data for Prosser Creek to determine beneficial use support and results are as follows: 0 of 15 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 Truckee River Watershed Council 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: MTRPROS02 (Prosser at Highway 89).

Temporal Representation:

The samples were collected between the dates of 2017-06-23 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 162611, pH	Region 6
Prosser Creek

LOE ID:

340144

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 Truckee River Watershed Council 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: MTRPROS01 (Prosser Creek below dam).

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 162611, pH	Region 6
Prosser Creek

LOE ID:

340024

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, WQ from the Truckee River Watershed Council 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: MTRPROS01 (Prosser Creek below dam).

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 162611, pH	Region 6
Prosser Creek

LOE ID:

339784

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 Truckee River Watershed Council 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: MTRPROS02 (Prosser at Highway 89).

Temporal Representation:

The samples were collected between the dates of 2017-06-23 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.


DECISION ID	170133	Region 6
Prosser Creek

Pollutant:	Specific Conductivity
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Original
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 170133, Specific Conductivity	Region 6
Prosser Creek

LOE ID:

340405

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:

Water Board staff assessed Truckee River Watershed Council data for Prosser Creek to determine beneficial use support and results are as follows: 0 of 12 samples exceeded the water quality threshold for SpecificConductivity.

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council 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: MTRPROS02 (Prosser at Highway 89).

Temporal Representation:

The samples were collected between the dates of 2017-05-20 and 2020-10-03

Environmental Conditions:

QAPP Information:

QAPP for Truckee River Monitoring Plan

QAPP Information Reference(s):

Quality Assurance Project Plan (QAPP) for Truckee River Monitoring Plan.

Line of Evidence (LOE) for Decision ID 170133, Specific Conductivity	Region 6
Prosser Creek

LOE ID:

340624

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:

Water Board staff assessed Truckee River Watershed Council data for Prosser Creek to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality threshold for SpecificConductivity.

Data Reference:

Benthic, Field, Habitat, WQ from the Truckee River Watershed Council 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: MTRPROS01 (Prosser Creek below dam).