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

Supporting Information

Regional Board 6 - Lahontan Region

Water Body Name:	Cascade Creek
Water Body ID:	CAR6341004020170901038600
Water Body Type:	River & Stream


DECISION ID	162643	Region 6
Cascade Creek

Pollutant:	Alkalinity as CaCO3
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:	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 162643, Alkalinity as CaCO3	Region 6
Cascade Creek

LOE ID:

337812

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:

Water Board staff assessed TRPA Tahoe Ambient Monitoring data for Cascade Creek to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.

Data Reference:

Benthic, Field, Habitat from the Tahoe Regional Planning Authority 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: 634TPA070 (Cascade Creek 634011070 Trend Panel A).

Temporal Representation:

The samples were collected between the dates of 2018-07-09 and 2018-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162643, Alkalinity as CaCO3	Region 6
Cascade Creek

LOE ID:

337982

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:

Water Board staff assessed SWAMP Reference Condition Management Plan data for Cascade Creek to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Alkalinity as CaCO3.

Data Reference:

Benthic, Field, Habitat, 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: 634CAS001 (Cascade Creek, below Snow Lake).

Temporal Representation:

The samples were collected between the dates of 2022-07-25 and 2022-07-25

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	171283	Region 6
Cascade 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:	Do Not List on 303(d) list (TMDL required list)(2018)
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. Two lines of evidence evaluating benthic-macroinvertebrate bioassessment data are available in the administrative record to assess this indicator. Zero of three benthic-macroinvertebrate samples exceed the California Stream Condition Index (CSCI) impairment threshold. These data indicate that the waterbody is likely unimpaired for Benthic Community Effects and therefore no other pollutant LOEs need be associated with this decision at this time. 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. Zero of three benthic-macroinvertebrate bioassessment samples had CSCI scores below 0.79. Therefore, this water body is not exceeding the water quality threshold for the protection of the COLD beneficial use. The available information indicates that the waterbody/pollutant combination should not be placed on the 303(d) List of impaired waters at this time. 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 171283, Benthic Community Effects	Region 6
Cascade Creek

LOE ID:

96795

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 water body had CSCI scores of 1.133346 and 0.96865 and is therefore not exceeding the water quality objective for the aquatic life beneficial use Additionally, this water body passed several screening criteria and was identified as a reference water body for the purposes of developing the CSCI. Reference sites where human disturbance is absent or minimal are used to set benchmark expectations for healthy streams. A large set of nearly 600 reference sites representing the broad diversity of natural stream types found across California was used to develop the CSCI.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for the SWAMP Reference Condition Management Plan (RCMP).

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:

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:

Samples collected at the following stations: 634CAS001, CAT08722-038

Temporal Representation:

Samples Collected on 8/15/2002 and 8/10/2009.

Environmental Conditions:

QAPP Information:

QAPP for SWAMP Reference Condition Management Plan.

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 171283, Benthic Community Effects	Region 6
Cascade Creek

LOE ID:

352863

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 634TPA070 to determine beneficial use support and the results are as follows: 0 of 1 samples exceeded the water quality standard. CSCI scores were from 0.821409 to 0.821409 .

Data Reference:

Benthic, Field, Habitat from the Tahoe Regional Planning Authority 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:

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: 634TPA070 (Cascade Creek 634011070 Trend Panel A).

Temporal Representation:

Samples were collected from 2018-07-09 to 2018-07-09.

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	163809	Region 6
Cascade Creek

Pollutant:	Chloride
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:	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 163809, Chloride	Region 6
Cascade Creek

LOE ID:

342766

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 League to Save Lake Tahoe Truckee Tahoe Snapshot D data to determine beneficial use support and results are as follows:
1 of 3 samples exceeded the water quality threshold for Chloride

Data Reference:

Field, WQ from the Truckee Tahoe Snapshot Day 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 0.4 (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: Cascade Creek at Mouth (SLT-CASC-00)

Temporal Representation:

The samples were collected between the dates of 2015-05-16 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 163809, Chloride	Region 6
Cascade Creek

LOE ID:

342776

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 League to Save Lake Tahoe Truckee Tahoe Snapshot D data to determine beneficial use support and results are as follows:
1 of 2 samples exceeded the water quality threshold for Chloride

Data Reference:

Field, WQ from the Truckee Tahoe Snapshot Day 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 0.4 (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: Cascade Creek above Highway 89 (SLT-CASC-01)

Temporal Representation:

The samples were collected between the dates of 2015-05-16 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634


DECISION ID	168731	Region 6
Cascade Creek

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:	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 168731, Indicator Bacteria	Region 6
Cascade Creek

LOE ID:

336794

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 League to Save Lake Tahoe Truckee Tahoe Snapshot D data for Cascade Creek to determine beneficial use support and the results are as follows: 0 of the 1 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:

Field, WQ from the Truckee Tahoe Snapshot Day for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-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): SLT-CASC-01 (Cascade Creek above Highway 89).

Temporal Representation:

The samples were collected between the days of 2013-05-11 and 2013-05-11 .

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 168731, Indicator Bacteria	Region 6
Cascade Creek

LOE ID:

336805

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 League to Save Lake Tahoe Truckee Tahoe Snapshot D data for Cascade Creek to determine beneficial use support and the results are as follows: 0 of the 3 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:

Field, WQ from the Truckee Tahoe Snapshot Day for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

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): SLT-CASC-00 (Cascade Creek at Mouth).

Temporal Representation:

The samples were collected between the days of 2013-05-11 and 2018-05-19 .

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 168731, Indicator Bacteria	Region 6
Cascade Creek

LOE ID:

129151

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 RWB6_BACT_Monitoring data for Cascade 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 Regional Water Board 6 Bacteria Monitoring.

SWAMP Data:

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): 634CASB10

Temporal Representation:

The samples were collected between the days of 2014-06-09 and 2015-06-01 .

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 168731, Indicator Bacteria	Region 6
Cascade Creek

LOE ID:

129470

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 RWB6_BACT_Monitoring data for Cascade 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 Regional Water Board 6 Bacteria 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), station(s): 634CASB10

Temporal Representation:

The samples were collected between the days of 2014-06-09 and 2015-06-01 .

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 168731, Indicator Bacteria	Region 6
Cascade Creek

LOE ID:

100018

Pollutant:

Escherichia coli (E. coli)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

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 RWB6_BACT_Monitoring data for Cascade Creek to determine beneficial use support and the results are as follows: 0 of the 1 samples 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 Regional Water Board 6 Bacteria Monitoring.

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(s), station(s): 634CASB10

Temporal Representation:

The samples were collected between the days of 2015-06-01 and 2015-06-01 .

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	168964	Region 6
Cascade Creek

Pollutant:	Nitrogen
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:	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 168964, Nitrogen	Region 6
Cascade Creek

LOE ID:

343093

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 League to Save Lake Tahoe Truckee Tahoe Snapshot D data to determine beneficial use support and results are as follows:
0 of 3 samples exceeded the water quality threshold for Nitrogen, Total

Data Reference:

Field, WQ from the Truckee Tahoe Snapshot Day 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 0.21 (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: Cascade Creek at Mouth (SLT-CASC-00)

Temporal Representation:

The samples were collected between the dates of 2016-05-14 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 168964, Nitrogen	Region 6
Cascade Creek

LOE ID:

343113

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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 League to Save Lake Tahoe Truckee Tahoe Snapshot D data to determine beneficial use support and results are as follows:
0 of 2 samples exceeded the water quality threshold for Nitrogen, Total

Data Reference:

Field, WQ from the Truckee Tahoe Snapshot Day 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 0.21 (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: Cascade Creek at Mouth (SLT-CASC-00)

Temporal Representation:

The samples were collected between the dates of 2009-05-16 and 2013-05-11

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 168964, Nitrogen	Region 6
Cascade Creek

LOE ID:

343116

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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 League to Save Lake Tahoe Truckee Tahoe Snapshot D data to determine beneficial use support and results are as follows:
0 of 1 samples exceeded the water quality threshold for Nitrogen, Total

Data Reference:

Field, WQ from the Truckee Tahoe Snapshot Day 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 0.21 (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: Cascade Creek above Highway 89 (SLT-CASC-01)

Temporal Representation:

The samples were collected between the dates of 2013-05-11 and 2013-05-11

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 168964, Nitrogen	Region 6
Cascade Creek

LOE ID:

343103

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:

Field, WQ from the Truckee Tahoe Snapshot Day 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 0.21 (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: Cascade Creek above Highway 89 (SLT-CASC-01)

Temporal Representation:

The samples were collected between the dates of 2016-05-14 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634


DECISION ID	169392	Region 6
Cascade Creek

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:	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 169392, Nitrogen, Nitrate	Region 6
Cascade Creek

LOE ID:

338932

Pollutant:

Nitrate as Nitrate (NO3)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

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 League to Save Lake Tahoe Truckee Tahoe Snapshot D data for Cascade Creek to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Nitrate as NO3.

Data Reference:

Field, WQ from the Truckee Tahoe Snapshot Day for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for Nitrate incorporated by reference in the Water Quality Control Plan, Lahontan Region is 45000 ug/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: SLT-CASC-00 (Cascade Creek at Mouth).

Temporal Representation:

The samples were collected between the dates of 2009-05-16 and 2011-05-14

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634


DECISION ID	162640	Region 6
Cascade Creek

Pollutant:	Oxygen, Dissolved
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. Five lines of evidence are available in the administrative record to assess this parameter: 4 which assess dissolved oxygen concentration data and 1 which assesses dissolved oxygen percent saturation data. Zero of 24 samples are below the objective for minimum dissolved oxygen concentration. One of 1 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. Zero of 24 samples are below the objective for minimum dissolved oxygen concentration. One of 1 samples is below the objective for minimum dissolved oxygen percent saturation. and this does not exceed the allowable number of exceedances 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. 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 162640, Oxygen, Dissolved	Region 6
Cascade Creek

LOE ID:

339045

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 League to Save Lake Tahoe Truckee Tahoe Snapshot D data for Cascade Creek to determine beneficial use support and results are as follows: 0 of 11 samples exceeded the water quality threshold for Oxygen, Dissolved.

Data Reference:

Field, WQ from the Truckee Tahoe Snapshot Day for the 2026 Integrated Report in Region 6

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 1 monitoring site: SLT-CASC-00 (Cascade Creek at Mouth).

Temporal Representation:

The samples were collected between the dates of 2003-05-10 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 162640, Oxygen, Dissolved	Region 6
Cascade Creek

LOE ID:

339303

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 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: 634CAS001 (Cascade Creek, below Snow Lake).

Temporal Representation:

The samples were collected between the dates of 2022-07-25 and 2022-07-25

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162640, Oxygen, Dissolved	Region 6
Cascade Creek

LOE ID:

339109

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:

Field, WQ from the Truckee Tahoe Snapshot Day 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: SLT-CASC-01 (Cascade Creek above Highway 89).

Temporal Representation:

The samples were collected between the dates of 2002-05-04 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 162640, Oxygen, Dissolved	Region 6
Cascade Creek

LOE ID:

339353

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:

Benthic, Field, Habitat from the Tahoe Regional Planning Authority for the 2026 Integrated Report in Region 6

SWAMP Data:

Non-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: 634TPA070 (Cascade Creek 634011070 Trend Panel A).

Temporal Representation:

The samples were collected between the dates of 2018-07-09 and 2018-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162640, Oxygen, Dissolved	Region 6
Cascade Creek

LOE ID:

339025

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 from the Tahoe Regional Planning Authority 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: 634TPA070 (Cascade Creek 634011070 Trend Panel A).

Temporal Representation:

The samples were collected between the dates of 2018-07-09 and 2018-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	168646	Region 6
Cascade 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	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. 0 of the 26 samples exceed the objective (MCL). 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 26 samples exceed the objective (MCL) 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 168646, Specific Conductivity	Region 6
Cascade Creek

LOE ID:

340533

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 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:

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: 634CAS001 (Cascade Creek, below Snow Lake).

Temporal Representation:

The samples were collected between the dates of 2022-07-25 and 2022-07-25

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 168646, Specific Conductivity	Region 6
Cascade Creek

LOE ID:

340471

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:

Field, WQ from the Truckee Tahoe Snapshot Day 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: SLT-CASC-00 (Cascade Creek at Mouth).

Temporal Representation:

The samples were collected between the dates of 2003-05-10 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 168646, Specific Conductivity	Region 6
Cascade Creek

LOE ID:

340571

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 from the Tahoe Regional Planning Authority 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: 634TPA070 (Cascade Creek 634011070 Trend Panel A).

Temporal Representation:

The samples were collected between the dates of 2018-07-09 and 2018-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 168646, Specific Conductivity	Region 6
Cascade Creek

LOE ID:

340370

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:

Field, WQ from the Truckee Tahoe Snapshot Day 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: SLT-CASC-01 (Cascade Creek above Highway 89).

Temporal Representation:

The samples were collected between the dates of 2002-05-04 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634


DECISION ID	162642	Region 6
Cascade Creek

Pollutant:	Turbidity
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:	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 162642, Turbidity	Region 6
Cascade Creek

LOE ID:

340933

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 League to Save Lake Tahoe Truckee Tahoe Snapshot D data for Cascade Creek to determine beneficial use support and results are as follows: 1 of 11 samples exceeded the water quality threshold for Turbidity.

Data Reference:

Field, WQ from the Truckee Tahoe Snapshot Day for the 2026 Integrated Report in Region 6

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 1 monitoring site: SLT-CASC-00 (Cascade Creek at Mouth).

Temporal Representation:

The samples were collected between the dates of 2003-05-10 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 162642, Turbidity	Region 6
Cascade Creek

LOE ID:

340903

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 League to Save Lake Tahoe Truckee Tahoe Snapshot D data for Cascade Creek to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality threshold for Turbidity.

Data Reference:

Field, WQ from the Truckee Tahoe Snapshot Day 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: SLT-CASC-01 (Cascade Creek above Highway 89).

Temporal Representation:

The samples were collected between the dates of 2002-05-04 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 162642, Turbidity	Region 6
Cascade Creek

LOE ID:

340875

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 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: 634CAS001 (Cascade Creek, below Snow Lake).

Temporal Representation:

The samples were collected between the dates of 2022-07-25 and 2022-07-25

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	162641	Region 6
Cascade Creek

Pollutant:	pH
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:	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 162641, pH	Region 6
Cascade Creek

LOE ID:

340014

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 League to Save Lake Tahoe Truckee Tahoe Snapshot D data for Cascade Creek to determine beneficial use support and results are as follows: 0 of 13 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:

Field, WQ from the Truckee Tahoe Snapshot Day 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: SLT-CASC-00 (Cascade Creek at Mouth).

Temporal Representation:

The samples were collected between the dates of 2003-05-10 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 162641, pH	Region 6
Cascade Creek

LOE ID:

339547

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 League to Save Lake Tahoe Truckee Tahoe Snapshot D data for Cascade Creek to determine beneficial use support and results are as follows: 0 of 9 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:

Field, WQ from the Truckee Tahoe Snapshot Day 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: SLT-CASC-01 (Cascade Creek above Highway 89).

Temporal Representation:

The samples were collected between the dates of 2010-05-22 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 162641, pH	Region 6
Cascade Creek

LOE ID:

340126

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 TRPA Tahoe Ambient Monitoring data for Cascade Creek 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 from the Tahoe Regional Planning Authority 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: 634TPA070 (Cascade Creek 634011070 Trend Panel A).

Temporal Representation:

The samples were collected between the dates of 2018-07-09 and 2018-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162641, pH	Region 6
Cascade Creek

LOE ID:

340208

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 Reference Condition Management Plan data for Cascade Creek 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 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: 634CAS001 (Cascade Creek, below Snow Lake).

Temporal Representation:

The samples were collected between the dates of 2022-07-25 and 2022-07-25

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162641, pH	Region 6
Cascade Creek

LOE ID:

339509

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 from the Tahoe Regional Planning Authority 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: 634TPA070 (Cascade Creek 634011070 Trend Panel A).

Temporal Representation:

The samples were collected between the dates of 2018-07-09 and 2018-07-09

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162641, pH	Region 6
Cascade Creek

LOE ID:

340156

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 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: 634CAS001 (Cascade Creek, below Snow Lake).

Temporal Representation:

The samples were collected between the dates of 2022-07-25 and 2022-07-25

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 162641, pH	Region 6
Cascade Creek

LOE ID:

340020

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:

Field, WQ from the Truckee Tahoe Snapshot Day 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: SLT-CASC-01 (Cascade Creek above Highway 89).

Temporal Representation:

The samples were collected between the dates of 2010-05-22 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634

Line of Evidence (LOE) for Decision ID 162641, pH	Region 6
Cascade Creek

LOE ID:

339770

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:

Field, WQ from the Truckee Tahoe Snapshot Day 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: SLT-CASC-00 (Cascade Creek at Mouth).

Temporal Representation:

The samples were collected between the dates of 2003-05-10 and 2018-05-19

Environmental Conditions:

QAPP Information:

Tahoe Truckee Snapshot QAPP

QAPP Information Reference(s):

Lahontan Water Board - TahoeTruckeeSnapshotQAPP - League to Save Lake Tahoe Truckee Tahoe Snapshot D - 402634