# Draft 2008 California 303(d)/305(b) Integrated Report

# Supporting Information

## Regional Board 5 - Central Valley Region

Water Body Name: | Willow Slough (Yolo County)
Water Body ID: | CAR5112000020080801153727
Water Body Type: | River & Stream

DECISION ID | 11489
Pollutant: | Chlorpyrifos
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
Weight of Evidence: | This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line(s) of evidence is available in the administrative record to assess this pollutant. One of the samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. One of 5 samples exceeded the 4-day average maximum concentration criterion and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. In addition, 1 of 5 available 1-hour average concentrations exceeded the 1-day average concentration criterion and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation: |
USEPA Decision: |

Lines of Evidence (LOEs) for Decision ID 11489

LOE ID: | 23289
Pollutant: | Chlorpyrifos
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Total
Beneficial Use: | Warm Freshwater Habitat
Aquatic Life Use: | Warm Freshwater Habitat
Number of Samples: | 5
Number of Exceedances: | 1
Data and Information Type: | PHYSICAL/CHEMICAL MONITORING
Data Used to Asses Water Quality: | Five water samples were collected from Willow Slough in 2004, representing 5 4-day average concentrations and 5 1-hour average concentrations.1 of 5 four-day average concentrations exceeded the four day maximum concentration guideline of 0.015 µg/L.1 of 5 one-hour average concentrations exceeded the maximum 1-hour chlorpyrifos concentration of 0.025 µg/L.
Data Reference: | Revised Draft of the 2007 Review of the Monitoring Data for the Irrigated Lands Regulatory Conditional Waiver Program
| Monitoring and Reporting Program, Order Nos. R5-2003-0826, R5-2005-0833, and R5-2008-0005 for Coalition Groups Under Resolution No. R5-2003-0105, Conditional Waiver of Waste Discharge Requirements for Discharges From Irrigated Lands Within the Central Valley Region
Water Quality Objective/Criterion: | No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses (CVRWQCB, 2007). All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life (CVRWQCB, 2007).
Objective/Criterion Reference: | Water quality criteria for diazinon and chlorpyrifos. Administrative Report 00-3. Rancho Cordova, CA: Pesticide Investigations Unit, Office of Spills and Response. CA Department of Fish and Game
| Central Valley Regional Water Quality Control Board. Water Quality Control Plan (Basin Plan) for the California Regional Water Quality Control Board - Central Valley Region
Evaluation Guideline: | California Department of Fish and Game Hazard Assessment Criteria - 0.015 µg/L 4-day average and 0.025 µg/L 1-hour average (Siepmann and Finlayson, 2000, with minor corrections to significant figures as described in Beaulaurier et al., 2005).
Guideline Reference: | Water quality criteria for diazinon and chlorpyrifos. Administrative Report 00-3. Rancho Cordova, CA: Pesticide Investigations Unit, Office of Spills and Response. CA Department of Fish and Game
Spatial Representation: | Samples were collected from Willow Slough at Road 99.
Temporal Representation: | Samples were collected from July through September 2004.
Environmental Conditions: |
QAPP Information: | Data quality: Good. Monitoring was conducted in accordance with Central Valley Water Board Monitoring and Reporting Program (order number R5-2003-0826) requirements (CVRWQCB, 2003)
QAPP Information Reference(s):

DECISION ID | 11496
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
Weight of Evidence: | This pollutant is being considered for placement on the 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. One line(s) of evidence is available in the administrative record to assess this pollutant. One of the samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. One of 6 samples exceeded the minimum criterion (5 mg/L) and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. In addition, 2 of 6 available data exceeded the minimum criterion (7 mg/L) 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation: |
USEPA Decision: |

Lines of Evidence (LOEs) for Decision ID 11496

LOE ID: | 23264
Pollutant: | Oxygen, Dissolved
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Total
Beneficial Use: | Cold Freshwater Habitat
Aquatic Life Use: | Cold Freshwater Habitat
Number of Samples: | 6
Number of Exceedances: | 1
Data and Information Type: | PHYSICAL/CHEMICAL MONITORING
Data Used to Asses Water Quality: | 6 samples were taken from Willow Slough from April 2003 to September 2004. 2 samples were below the minimum dissolved oxygen concentration (7 mg/L) and 1 sample was below 5 mg/L.
Data Reference: | Revised Draft of the 2007 Review of the Monitoring Data for the Irrigated Lands Regulatory Conditional Waiver Program
| Monitoring and Reporting Program, Order Nos. R5-2003-0826, R5-2005-0833, and R5-2008-0005 for Coalition Groups Under Resolution No. R5-2003-0105, Conditional Waiver of Waste Discharge Requirements for Discharges From Irrigated Lands Within the Central Valley Region
Water Quality Objective/Criterion: | Sacramento/San Joaquin River Basin Plan (CVRWQCB. 2007a)(COLD), Minimum Dissolved Oxygen concentration of 7mg/L(SPWN), Minimum Dissolved Oxygen concentration of 7 mg/L(WARM), Minimum Dissolved Oxygen concentration of 5 mg/L
Objective/Criterion Reference: | Central Valley Regional Water Quality Control Board. Water Quality Control Plan (Basin Plan) for the California Regional Water Quality Control Board - Central Valley Region
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | Samples were collected from Willow Slough at Road 99 and Road 27.
Temporal Representation: | Samples were collected between April 2003 and September 2004 at variable intervals (biweekly, monthly).
Environmental Conditions: |
QAPP Information: | Data quality: Good. Monitoring was conducted in accordance with Central Valley Water Board Monitoring and Reporting Program (order number R5-2003-0826) requirements (CVRWQCB, 2003)
QAPP Information Reference(s):

DECISION ID | 11497
Pollutant: | Salinity
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
Weight of Evidence: | This pollutant is being considered for placement on the section 303(d) list under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. One of the samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. One of 11 samples exceeded the the water quality objectives for electrical conductivity and total dissolved solids (collectively salinity) 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation: |
USEPA Decision: |

Lines of Evidence (LOEs) for Decision ID 11497

LOE ID: | 23288
Pollutant: | Salinity
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Total
Beneficial Use: | Municipal & Domestic Supply
Number of Samples: | 5
Number of Exceedances: | 0
Data and Information Type: | PHYSICAL/CHEMICAL MONITORING
Data Used to Asses Water Quality: | Five measurements of Total Dissolved Solids (TDS) were taken from Willow Slough between July and September 2004. Zero of the 5 measurements exceed the California Secondary MCL for TDS in surface water.
Data Reference: | Revised Draft of the 2007 Review of the Monitoring Data for the Irrigated Lands Regulatory Conditional Waiver Program
| Monitoring and Reporting Program, Order Nos. R5-2003-0826, R5-2005-0833, and R5-2008-0005 for Coalition Groups Under Resolution No. R5-2003-0105, Conditional Waiver of Waste Discharge Requirements for Discharges From Irrigated Lands Within the Central Valley Region
Water Quality Objective/Criterion: | The water quality objective used was the California Secondary MCL of 500 mg/L. The Basin Plan includes chemical constituent water quality objectives that include (by reference) secondary maximum contaminant levels (MCLs) protective of MUN (CVRWQCB, 2007a). The secondary MCLs for TDS provide a range of values including a recommended level (500 mg/L), upper level (1000 mg/L) and a short-term level (1500 mg/L). The ¿recommended¿ concentration was used as it is intended to be protective of all drinking water uses. Though individual listing evaluations did not look at the water supply source serving the given geographic area, there are certain areas that receive supply waters (such as the Delta Mendota Canal) that at times may be elevated above the recommended level of the secondary MCL. Where future information is made available to document this to be the case, these water bodies may be re-evaluated in future listing cycles. TDS levels should not exceed 500 mg/L (CVRWQCB, 2007a).
Objective/Criterion Reference: | Central Valley Regional Water Quality Control Board. Water Quality Control Plan (Basin Plan) for the California Regional Water Quality Control Board - Central Valley Region
| California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring. http://www.cdph.ca.gov/certlic/drinkingwater/Pages/Lawbook.aspx
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | TDS was measured in Willow Slough at Road 99 and Road 27, in Yolo County.
Temporal Representation: | TDS was measured between July 2004 and September 2004. Measurements were made at approximately biweekly.Willow Slough is a tributary to the Yolo Bypass.
Environmental Conditions: |
QAPP Information: | Data quality: Good. Monitoring was conducted in accordance with Central Valley Water Board Monitoring and Reporting Program (order number R5-2003-0826) requirements (CVRWQCB, 2003)
QAPP Information Reference(s):
LOE ID: | 23287
Pollutant: | Salinity
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Total
Beneficial Use: | Municipal & Domestic Supply
Number of Samples: | 6
Number of Exceedances: | 1
Data and Information Type: | PHYSICAL/CHEMICAL MONITORING
Data Used to Asses Water Quality: | Six measurements of Specific Conductivity were taken from Willow Slough between April 2003 and September 2004. One of the 6 measurements exceeds the California Secondary MCL for Electrical Conductivity in surface water.
Data Reference: | Revised Draft of the 2007 Review of the Monitoring Data for the Irrigated Lands Regulatory Conditional Waiver Program
| Monitoring and Reporting Program, Order Nos. R5-2003-0826, R5-2005-0833, and R5-2008-0005 for Coalition Groups Under Resolution No. R5-2003-0105, Conditional Waiver of Waste Discharge Requirements for Discharges From Irrigated Lands Within the Central Valley Region
Water Quality Objective/Criterion: | The water quality objective used was the California Secondary MCL recommended level of 900 uS/cm. The Basin Plan includes chemical constituent water quality objectives that include (by reference) secondary maximum contaminant levels (MCLs) protective of MUN (CVRWQCB, 2007a). The secondary MCLs for electrical conductivity provide a range of values including a recommended level (900 uS/cm), an upper level (1600 uS/cm), and a short-term level (2200 uS/cm). The ¿recommended¿ concentration was used as it is intended to be protective of all drinking water uses. Though individual listing evaluations did not look at the water supply source serving the given geographic area, there are certain areas that receive supply waters (such as the Delta Mendota Canal) that at times may be elevated above the recommended level of the Secondary MCL. Where future information is made available to document this to be the case, these water bodies may be re-evaluated in future listing cycles. Specific (Electrical) Conductivity levels should not exceed 900 uS/cm (CVRWQCB, 2007a).
Objective/Criterion Reference: | Central Valley Regional Water Quality Control Board. Water Quality Control Plan (Basin Plan) for the California Regional Water Quality Control Board - Central Valley Region
| California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring. http://www.cdph.ca.gov/certlic/drinkingwater/Pages/Lawbook.aspx
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | Specific Conductivity was measured in Willow Slough at Road 99 and Road 27, in Yolo County.
Temporal Representation: | Specific Conductivity was measured between April 2003 and September 2004. Measurements were made at intervals ranging from biweekly to quarterly.Willow Slough is a tributary to the Yolo Bypass.
Environmental Conditions: |
QAPP Information: | Data quality: Good. Monitoring was conducted in accordance with Central Valley Water Board Monitoring and Reporting Program (order number R5-2003-0826) requirements (CVRWQCB, 2003)
QAPP Information Reference(s):

DECISION ID | 11498
Pollutant: | Sediment Toxicity
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
Weight of Evidence: | This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a one line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. The single sample did not exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used does not satisfy the data quantity requirements of section 6.1.5 of the Policy. 3. Zero of one sample tested with Hyalella azteca (an invertebrate species) exceeded the narrative toxicity objective; however, this sample size is insufficient to determine with the power and confidence of the Listing Policy if standards are not met. A minimum of two samples is needed for application of 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.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation: |
USEPA Decision: |

Lines of Evidence (LOEs) for Decision ID 11498

LOE ID: | 23280
Pollutant: | Toxicity
LOE Subgroup: | Toxicity
Matrix: | Sediment
Fraction: | Total
Beneficial Use: | Warm Freshwater Habitat
Aquatic Life Use: | Warm Freshwater Habitat
Number of Samples: | 1
Number of Exceedances: | 0
Data and Information Type: | TOXICITY TESTING
Data Used to Asses Water Quality: | Data is available for a single sample collected on 19 August 2004. The sample, tested with Hyalella azteca, was not toxic and did not violate the narrative toxicity objective.
Data Reference: | Revised Draft of the 2007 Review of the Monitoring Data for the Irrigated Lands Regulatory Conditional Waiver Program
| Monitoring and Reporting Program, Order Nos. R5-2003-0826, R5-2005-0833, and R5-2008-0005 for Coalition Groups Under Resolution No. R5-2003-0105, Conditional Waiver of Waste Discharge Requirements for Discharges From Irrigated Lands Within the Central Valley Region
Water Quality Objective/Criterion: | All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life. This objective applies regardless of whether the toxicity is caused by a single substance or the interactive effect of multiple substances (CVRWQCB, 2007).
Objective/Criterion Reference: | Central Valley Regional Water Quality Control Board. Water Quality Control Plan (Basin Plan) for the California Regional Water Quality Control Board - Central Valley Region
Evaluation Guideline: | Statistically significant difference from control sediment using Dunnett's test in 10-day Hyalella azteca sediment toxicity tests. Arcsin squareroot transformation was used when necessary to meet the assumptions of normality and homogeneity of variance. Steel's Many-One Rank Test was used for comparison to control if these assumptions were not met after transformation.
Guideline Reference: | Methods for Measuring the Toxicity and Bioaccumulation of Sediment-associated Contaminants with Freshwater Invertebrates, Second Edition. U.S. Environmental Protection Agency Office of Research and Development, Duluth, MI , U.S. Environmental Protection Agency Office of Water, Washington, DC EPA-600/R-99/064
Spatial Representation: | The sample was collected from Willow Slough at Road 99.
Temporal Representation: | The sample was collected on 19 August 2004.
Environmental Conditions: |
QAPP Information: | Data quality: Excellent. Monitoring was conducted in accordance with Central Valley Water Board Monitoring and Reporting Program (order number R5-2003-0826) requirements (CVRWQCB, 2003)
QAPP Information Reference(s):

DECISION ID | 11499
Pollutant: | Unknown Toxicity
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
Weight of Evidence: | This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Three lines of evidence are available in the administrative record to assess this pollutant. None of the samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. None of 6 samples tested with Ceriodaphnia dubia (an invertebrate species) exceeded the narrative toxicity objective and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. In addition, none of 6 samples tested with Pimephales promelas (Fathead Minnow, a vertebrate species) exceeded the narrative toxicity objective and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. Lastly, none of 5 samples tested with Selenastrum capricornutum (an algal species) exceeded the narrative toxicity objective and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff 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.
SWRCB Board Decision / Staff Recommendation: |
USEPA Decision: |

Lines of Evidence (LOEs) for Decision ID 11499

LOE ID: | 23271
Pollutant: | Toxicity
LOE Subgroup: | Toxicity
Matrix: | Water
Fraction: | Total
Beneficial Use: | Warm Freshwater Habitat
Aquatic Life Use: | Warm Freshwater Habitat
Number of Samples: | 6
Number of Exceedances: | 0
Data and Information Type: | TOXICITY TESTING
Data Used to Asses Water Quality: | None of the 6 samples tested with Ceriodaphnia dubia were toxic and violated the narrative toxicity objective. The following is a summary of test results by site. Willow Slough at Road 99 - None of the 5 samples were toxic and violated the narrative toxicity objective. Willow Slough at Road 27 - The site was sampled once on 8 April 2003. This single sample was not toxic and did not violate the narrative toxicity objective.
Data Reference: | Revised Draft of the 2007 Review of the Monitoring Data for the Irrigated Lands Regulatory Conditional Waiver Program
| Monitoring and Reporting Program, Order Nos. R5-2003-0826, R5-2005-0833, and R5-2008-0005 for Coalition Groups Under Resolution No. R5-2003-0105, Conditional Waiver of Waste Discharge Requirements for Discharges From Irrigated Lands Within the Central Valley Region
Water Quality Objective/Criterion: | All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life. This objective applies regardless of whether the toxicity is caused by a single substance or the interactive effect of multiple substances (CVRWQCB, 2007).
Objective/Criterion Reference: | Central Valley Regional Water Quality Control Board. Water Quality Control Plan (Basin Plan) for the California Regional Water Quality Control Board - Central Valley Region
Evaluation Guideline: | Statistically significant difference from control using a t-test with 4-day acute-style toxicity tests (USEPA 2002).
Guideline Reference: | Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, Fifth Edition. U.S. Environmental Protection Agency Office of Water, Washington, DC EPA-821-R-02-012
Spatial Representation: | Samples were collected from Willow Slough at Road 99 and Road 27.
Temporal Representation: | Samples were collected from Willow Slough at Road 99 on the following dates: 8 July 2004, 22 July 2004, 5 August 2004, 19 August 2004, and 2 September 2004. Willow Slough at Road 27 was sampled once on 8 April 2003.
Environmental Conditions: |
QAPP Information: | Data quality: Excellent. Monitoring was conducted in accordance with Central Valley Water Board Monitoring and Reporting Program (order number R5-2003-0826) requirements (CVRWQCB, 2003)
QAPP Information Reference(s): | Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, Fifth Edition. EPA-821-R-02-012
LOE ID: | 23282
Pollutant: | Toxicity
LOE Subgroup: | Toxicity
Matrix: | Water
Fraction: | Total
Beneficial Use: | Warm Freshwater Habitat
Aquatic Life Use: | Warm Freshwater Habitat
Number of Samples: | 5
Number of Exceedances: | 0
Data and Information Type: | TOXICITY TESTING
Data Used to Asses Water Quality: | None of the 5 samples tested with Selenastrum capricornutum were toxic and violated the narrative toxicity objective.
Data Reference: | Revised Draft of the 2007 Review of the Monitoring Data for the Irrigated Lands Regulatory Conditional Waiver Program
| Monitoring and Reporting Program, Order Nos. R5-2003-0826, R5-2005-0833, and R5-2008-0005 for Coalition Groups Under Resolution No. R5-2003-0105, Conditional Waiver of Waste Discharge Requirements for Discharges From Irrigated Lands Within the Central Valley Region
Water Quality Objective/Criterion: | All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life. This objective applies regardless of whether the toxicity is caused by a single substance or the interactive effect of multiple substances (CVRWQCB, 2007).
Objective/Criterion Reference: | Central Valley Regional Water Quality Control Board. Water Quality Control Plan (Basin Plan) for the California Regional Water Quality Control Board - Central Valley Region
Evaluation Guideline: | Statistically significant difference from control using a t-test with 4-day chronic-style toxicity tests.
Guideline Reference: | Short-term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, Fourth Edition. U.S. Environmental Protection Agency Office of Water, Washington, DC EPA-821-R-02-013
Spatial Representation: | Samples were collected from Willow Slough at Road 99.
Temporal Representation: | Samples were collected on the following dates: 8 July 2004, 22 July 2004, 5 August 2004, 19 August 2004, and 2 September 2004.
Environmental Conditions: |
QAPP Information: | Data quality: Excellent. Monitoring was conducted in accordance with Central Valley Water Board Monitoring and Reporting Program (order number R5-2003-0826) requirements (CVRWQCB, 2003)
QAPP Information Reference(s): | Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, Fifth Edition. EPA-821-R-02-012
LOE ID: | 23281
Pollutant: | Toxicity
LOE Subgroup: | Toxicity
Matrix: | Water
Fraction: | Total
Beneficial Use: | Warm Freshwater Habitat
Aquatic Life Use: | Warm Freshwater Habitat
Number of Samples: | 6
Number of Exceedances: | 0
Data and Information Type: | TOXICITY TESTING
Data Used to Asses Water Quality: | None of the 6 samples tested with Pimephales promelas were toxic and violated the narrative toxicity objective. The following is a summary of test results by site. Willow Slough at Road 99 - None of the 5 samples were toxic and violated the narrative toxicity objective. Willow Slough at Road 27 - The site was sampled once on 8 April 2003. This single sample was not toxic and did not violate the narrative toxicity objective.
Data Reference: | Revised Draft of the 2007 Review of the Monitoring Data for the Irrigated Lands Regulatory Conditional Waiver Program
| Monitoring and Reporting Program, Order Nos. R5-2003-0826, R5-2005-0833, and R5-2008-0005 for Coalition Groups Under Resolution No. R5-2003-0105, Conditional Waiver of Waste Discharge Requirements for Discharges From Irrigated Lands Within the Central Valley Region
Water Quality Objective/Criterion: | All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life. This objective applies regardless of whether the toxicity is caused by a single substance or the interactive effect of multiple substances (CVRWQCB, 2007).
Objective/Criterion Reference: | Central Valley Regional Water Quality Control Board. Water Quality Control Plan (Basin Plan) for the California Regional Water Quality Control Board - Central Valley Region
Evaluation Guideline: | Statistically significant difference from control using a t-test with 4-day acute-style toxicity tests (USEPA 2002).
Guideline Reference: | Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, Fifth Edition. U.S. Environmental Protection Agency Office of Water, Washington, DC EPA-821-R-02-012
Spatial Representation: | Samples were collected from Willow Slough at Road 99 and Road 27.
Temporal Representation: | Samples were collected from Willow Slough at Road 99 on the following dates: 8 July 2004, 22 July 2004, 5 August 2004, 19 August 2004, and 2 September 2004. Willow Slough at Road 27 was sampled once on 8 April 2003.
Environmental Conditions: |
QAPP Information: | Data quality: Excellent. Monitoring was conducted in accordance with Central Valley Water Board Monitoring and Reporting Program (order number R5-2003-0826) requirements (CVRWQCB, 2003)
QAPP Information Reference(s): | Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, Fifth Edition. EPA-821-R-02-012

DECISION ID | 11488
Pollutant: | Boron
Final Listing Decision: | List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision: | New Decision
Revision Status | Revised
Sources: | Agriculture
Expected TMDL Completion Date: | 2021
Impairment from Pollutant or Pollution: | Pollutant
Weight of Evidence: | This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line(s) of evidence is available in the administrative record to assess this pollutant. Five of the samples exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Five of 5 samples exceeded the water quality objective and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
RWQCB Board Decision / Staff Recommendation: | After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.
SWRCB Board Decision / Staff Recommendation: |
USEPA Decision: |

Lines of Evidence (LOEs) for Decision ID 11488

LOE ID: | 23286
Pollutant: | Boron
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Total
Beneficial Use: | Agricultural Supply
Number of Samples: | 5
Number of Exceedances: | 5
Data and Information Type: | PHYSICAL/CHEMICAL MONITORING
Data Used to Asses Water Quality: | Five water samples were collected biweekly from Willow Slough between July 8 2004 and September 2 2004. Five of 5 concentrations exceeded the evaluation guideline for Boron.
Data Reference: | Revised Draft of the 2007 Review of the Monitoring Data for the Irrigated Lands Regulatory Conditional Waiver Program
| Monitoring and Reporting Program, Order Nos. R5-2003-0826, R5-2005-0833, and R5-2008-0005 for Coalition Groups Under Resolution No. R5-2003-0105, Conditional Waiver of Waste Discharge Requirements for Discharges From Irrigated Lands Within the Central Valley Region
Water Quality Objective/Criterion: | All waters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life (CVRWQCB, 2007).
Objective/Criterion Reference: | Central Valley Regional Water Quality Control Board. Water Quality Control Plan (Basin Plan) for the California Regional Water Quality Control Board - Central Valley Region
Evaluation Guideline: | Boron levels should not exceed the Agricultural Water Quality Goal for Boron of 700 ug/L (Ayers and Westcott, 1985).
Guideline Reference: | Water Quality for Agriculture, Food and Agriculture Organization of the United Nations - Irrigation and Drainage Paper No. 29, Rev 1, Rome (1985)
Spatial Representation: | Samples were collected from Willow Slough at Road 99.
Temporal Representation: | Samples were collected at approximately biweekly intervals from July 8 2004 to September 2 2004.Willow Slough is a tributary to the Yolo Bypass.
Environmental Conditions: |
QAPP Information: | Data quality: Good. Monitoring was conducted in accordance with Central Valley Water Board Monitoring and Reporting Program (order number R5-2003-0826) requirements (CVRWQCB, 2003)
QAPP Information Reference(s):