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

# Supporting Information

## Regional Board 5 - Central Valley Region

Water Body Name: | Willow Slough Bypass (Yolo County)
Water Body ID: | CAR5112000020080801152942
Water Body Type: | River & Stream

DECISION ID | 11458
Pollutant: | DDD (Dichlorodiphenyldichloroethane)
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. 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. Zero of 2 samples exceeded the water quality 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 11458

LOE ID: | 23272
Pollutant: | DDD (Dichlorodiphenyldichloroethane)
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Total
Beneficial Use: | Commercial or recreational collection of fish, shellfish, or organisms
Number of Samples: | 2
Number of Exceedances: | 0
Data and Information Type: | PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: | Five water samples were collected from Willow Slough between November 2003 and June 2004. None of the Five samples exceed the California Toxic Rule/USEPA (CTR/USEPA) criteria limit of 0.00059 ug/L for DDD based on a human health carcinogenic risk level of 10-6 for consumption of water and aquatic organisms. - Three samples had a high Reporting Limit hence the data could not be used in the analysis for exceedance (Listing Policy, Section 6.5.1.1) (SWRCB, 2004).
Data Reference: | Yolo Bypass Water Quality Management Plan Report. Prepared under CALFED Watershed Grant, Agreement # 4600001691 for the City of Woodland
Water Quality Objective/Criterion: | Sacramento/San Joaquin River Basin Plan (CVRWQCB, 2007)Pesticides: Total identifiable persistent chlorinated hydrocarbon pesticides shall not be present in the water column at concentrations detectable within the accuracy of analytical methods approved by the Environmental Protection Agency or the Executive Officer.- California Toxics Rule Criteria (USEPA, 2000)Inland Surface Waters based on drinking water and aquatic organism consumption. The criteria are based on human health protection for carcinogenicity at 1-in-a-million risk level (30-day average) with a limit of 0.00083 ug/L for DDD.
Objective/Criterion Reference: | Water Quality Standards 2000. Establishment of numeric criteria for priority toxic pollutants for the State of California: Rules and regulations. Federal Register Vol. 65, No. 97. Washington, D.C.: Environmental Protection Agency
| 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 an input channel of Willow Slough Bypass in Yolo County, California.
Temporal Representation: | Samples were collected between November 2003 and September 2004 at irregular intervals.
Environmental Conditions: |
QAPP Information: | Data quality: Good. Monitoring was conducted in accordance with the Quality Assurance Project Plan For Water Quality Monitoring For The Yolo Bypass Watershed Planning Project, 2003-2004
QAPP Information Reference(s):

DECISION ID | 11482
Pollutant: | DDE (Dichlorodiphenyldichloroethylene)
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. 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 5 samples exceeded the California Toxic Rule/USEPA (CTR/USEPA) criteria limit of 0.00059 μg/L for total DDE based on a human health carcinogenic risk level of 10-6 for consumption of water and aquatic organisms 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 11482

LOE ID: | 23273
Pollutant: | DDE (Dichlorodiphenyldichloroethylene)
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Total
Beneficial Use: | Commercial or recreational collection of fish, shellfish, or organisms
Number of Samples: | 5
Number of Exceedances: | 0
Data and Information Type: | PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: | Five samples were collected from Willow Slough between November 2003 and June 2004. None of the Five samples exceed the California Toxic Rule/USEPA (CTR/USEPA) criteria limit of 0.00059 ug/L for DDE based on a human health carcinogenic risk level of 10-6 for consumption of water and aquatic organisms. - All samples had a high Reporting Limit hence the data could not be used in the analysis for exceedance (Listing Policy, Section 6.5.1.1) (SWRCB, 2004).
Data Reference: | Yolo Bypass Water Quality Management Plan Report. Prepared under CALFED Watershed Grant, Agreement # 4600001691 for the City of Woodland
Water Quality Objective/Criterion: | California Toxics Rule Criterion for Inland Surface Waters based on drinking water and aquatic organism consumption. The criterion is based on human health protection for carcinogenicity at 1-in-a-million risk level (30-day average) with a limit of 0.00059 ug/L for DDE (USEPA, 2000).
Objective/Criterion Reference: | Water Quality Standards 2000. Establishment of numeric criteria for priority toxic pollutants for the State of California: Rules and regulations. Federal Register Vol. 65, No. 97. Washington, D.C.: Environmental Protection Agency
| 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 an input channel of Willow Slough Bypass in Yolo County, California.
Temporal Representation: | Samples were collected between November 2003 and September 2004 at irregular intervals.
Environmental Conditions: |
QAPP Information: | Data quality: Good. Monitoring was conducted in accordance with the Quality Assurance Project Plan For Water Quality Monitoring For The Yolo Bypass Watershed Planning Project, 2003-2004
QAPP Information Reference(s):

DECISION ID | 11483
Pollutant: | DDT (Dichlorodiphenyltrichloroethane)
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. 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 exceeded the California Toxic Rule/USEPA (CTR/USEPA) criteria limit of 0.00059 μg/L for total DDT based on a human health carcinogenic risk level of 10-6 for consumption of water 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 11483

LOE ID: | 23274
Pollutant: | DDT (Dichlorodiphenyltrichloroethane)
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Total
Beneficial Use: | Commercial or recreational collection of fish, shellfish, or organisms
Number of Samples: | 6
Number of Exceedances: | 0
Data and Information Type: | PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: | Six water samples were collected from Willow Slough between November 2003 and June 2004. None of the Six samples exceed the California Toxic Rule/USEPA (CTR/USEPA) criteria limit of 0.00059 ug/L for DDT based on a human health carcinogenic risk level of 10-6 for consumption of water and aquatic organisms. - Five water samples had a high Reporting Limit hence the data was not used in the analysis for exceedance (Listing Policy, Section 6.5.1.1) (SWRCB, 2004).
Data Reference: | Yolo Bypass Water Quality Management Plan Report. Prepared under CALFED Watershed Grant, Agreement # 4600001691 for the City of Woodland
Water Quality Objective/Criterion: | California Toxics Rule Criterion for Inland Surface Waters based on drinking water and aquatic organism consumption. The criterion is based on human health protection for carcinogenicity at 1-in-a-million risk level (30-day average) with a limit of 0.00059 ug/L for DDT (USEPA, 2000).
Objective/Criterion Reference: | Water Quality Standards 2000. Establishment of numeric criteria for priority toxic pollutants for the State of California: Rules and regulations. Federal Register Vol. 65, No. 97. Washington, D.C.: Environmental Protection Agency
| 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 an input channel of Willow Slough Bypass in Yolo County, California.
Temporal Representation: | Samples were collected between November 2003 and September 2004 at irregular intervals.
Environmental Conditions: |
QAPP Information: | Data quality: Good. Monitoring was conducted in accordance with the Quality Assurance Project Plan For Water Quality Monitoring For The Yolo Bypass Watershed Planning Project, 2003-2004
QAPP Information Reference(s):

DECISION ID | 11484
Pollutant: | Dieldrin
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. 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 exceeded the California Toxic Rule /USEPA (CTR/USEPA) criteria of 0.00014 μg/L for dieldrin based on continuous concentration (30-day average) for freshwater for aquatic life protection 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 11484

LOE ID: | 23275
Pollutant: | Dieldrin
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Total
Beneficial Use: | Commercial or recreational collection of fish, shellfish, or organisms
Number of Samples: | 6
Number of Exceedances: | 0
Data and Information Type: | PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: | - Six samples were collected from Willow Slough between November 2003 and September 2004. None of the Six samples exceeded the CTR criteria limit of 0.00014 ug/L for dieldrin (inland surface waters) based on continuous concentration (30-day average) for freshwater for aquatic life protection.- Three of the Six samples had a high Reporting Limit hence the data could not be used in the analysis for exceedance (Listing Policy, Section 6.5.1.1) (SWRCB, 2004).
Data Reference: | Yolo Bypass Water Quality Management Plan Report. Prepared under CALFED Watershed Grant, Agreement # 4600001691 for the City of Woodland
Water Quality Objective/Criterion: | California Toxics Rule criterion of 0.00014 ug/L for dieldrin (inland surface waters) based on continuous concentration (30-day average) for freshwater for aquatic life protection (USEPA, 2000).
Objective/Criterion Reference: | Water Quality Standards 2000. Establishment of numeric criteria for priority toxic pollutants for the State of California: Rules and regulations. Federal Register Vol. 65, No. 97. Washington, D.C.: Environmental Protection Agency
| 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 an input channel of Willow Slough Bypass in Yolo County, California.
Temporal Representation: | Samples were collected between November 2003 and September 2004 at irregular intervals.
Environmental Conditions: |
QAPP Information: | Data quality: Good. Monitoring was conducted in accordance with the Quality Assurance Project Plan For Water Quality Monitoring For The Yolo Bypass Watershed Planning Project, 2003-2004
QAPP Information Reference(s):

DECISION ID | 11487
Pollutant: | Selenium
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. 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 exceeded the California Toxics Rule (CTR) 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 11487

LOE ID: | 23283
Pollutant: | Selenium
LOE Subgroup: | Pollutant-Water
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: | PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: | Water samples were collected on 6 occasions and analyzed for total recoverable and dissolved Se. The range of concentrations in total recoverable samples was 2-5 ?g/L. The concentrations in the April total recoverable sample equaled the CTR criterion. The range of concentrations in dissolved samples was 2-4??g/L.
Data Reference: | Yolo Bypass Water Quality Management Plan Report. Prepared under CALFED Watershed Grant, Agreement # 4600001691 for the City of Woodland
Water Quality Objective/Criterion: | CTR criterion of 5 ug/L, total recoverable Se, for the protection of freshwater aquatic life (4-day average concentration to protect from extended period of exposure).
Objective/Criterion Reference: | Water Quality Standards 2000. Establishment of numeric criteria for priority toxic pollutants for the State of California: Rules and regulations. Federal Register Vol. 65, No. 97. Washington, D.C.: Environmental Protection Agency
| 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: | The CTR criterion is expressed as total recoverable Se (USEPA, 2000). Because this dataset reported that most of the selenium in the samples was dissolved (i.e., was detected in the filtered fraction), the data for dissolved samples were also compared with the criterion.
Guideline Reference: | Water Quality Standards 2000. Establishment of numeric criteria for priority toxic pollutants for the State of California: Rules and regulations. Federal Register Vol. 65, No. 97. Washington, D.C.: Environmental Protection Agency
Spatial Representation: | Samples were collected from an input channel of Willow Slough Bypass in Yolo County, California.
Temporal Representation: | Samples were collected on: 11/22/03, 1/23/04, 4/23/04, 6/26/04, 8/20/04, and 9/22/04.
Environmental Conditions: |
QAPP Information: | Data quality: Good. Monitoring was conducted in accordance with the Quality Assurance Project Plan For Water Quality Monitoring For The Yolo Bypass Watershed Planning Project, 2003-2004
QAPP Information Reference(s):

DECISION ID | 11457
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 | Natural Sources
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. Two line(s) of evidence is available in the administrative record to assess this pollutant. Six 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. Six of 6 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 11457

LOE ID: | 23285
Pollutant: | Boron
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Dissolved
Beneficial Use: | Agricultural Supply
Number of Samples: | 6
Number of Exceedances: | 6
Data and Information Type: | PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: | The Quality Assurance Project Plan for Water Quality Monitoring for the Yolo Bypass Watershed Planning Project (QAPP; LWA, 2003) indicates that water samples were planned to be collected from Willow Slough Bypass approximately bimonthly between November 22 2003 and September 22 2004. According to the QAPP, three separate water samples were to be collected at Willow Slough Bypass on 1/23/2004 - one each primary, field duplicate (FD), and field blank (FB). However, the data provided indicates that only a primary and a -FB- sample were collected. The primary and -FB- sample results are identical, both for total and dissolved boron. The results for the samples collected on 1/23/2004 are similar in magnitude to the primary sample results for samples collected in Willow Slough Bypass on the other sample dates. It appears reasonable that the data reported for samples collected from Willow Slough Bypass on 1/23/2004 are for the primary and duplicate samples and 6 of 6 dissolved Boron concentrations exceeded the evaluation guideline for Boron.
Data Reference: | Yolo Bypass Water Quality Management Plan Report. Prepared under CALFED Watershed Grant, Agreement # 4600001691 for the City of Woodland
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 at the lower end of Willow Slough Bypass.
Temporal Representation: | Samples were collected approximately bimonthly from November 22 2003 to September 22 2004. Willow Slough Bypass extends from Willow Slough near the Southern Pacific Railroad bridge, eastward to the Yolo Bypass.
Environmental Conditions: |
QAPP Information: | Data quality: Good. Monitoring was conducted in accordance with the Quality Assurance Project Plan For Water Quality Monitoring For The Yolo Bypass Watershed Planning Project, 2003-2004
QAPP Information Reference(s):
LOE ID: | 23284
Pollutant: | Boron
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Total
Beneficial Use: | Agricultural Supply
Number of Samples: | 6
Number of Exceedances: | 6
Data and Information Type: | PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: | The Quality Assurance Project Plan for Water Quality Monitoring for the Yolo Bypass Watershed Planning Project (QAPP; LWA, 2003) indicates that water samples were planned to be collected from Willow Slough Bypass approximately bimonthly between November 22 2003 and September 22 2004. According to the QAPP, three separate water samples were to be collected at Willow Slough Bypass on 1/23/2004 - one each primary, field duplicate (FD), and field blank (FB). However, the data provided indicates that only a primary and a -FB- sample were collected. The primary and -FB- sample results are identical, both for total and dissolved boron. The results for the samples collected on 1/23/2004 are similar in magnitude to the primary sample results for samples collected in Willow Slough Bypass on the other sample dates. It appears reasonable that the data reported for samples collected from Willow Slough Bypass on 1/23/2004 are for the primary and duplicate samples and 6 of 6 total Boron concentrations exceeded the evaluation guideline for Boron.
Data Reference: | Yolo Bypass Water Quality Management Plan Report. Prepared under CALFED Watershed Grant, Agreement # 4600001691 for the City of Woodland
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 at the lower end of Willow Slough Bypass.
Temporal Representation: | Samples were collected approximately bimonthly from November 22 2003 to September 22 2004. Willow Slough Bypass extends from Willow Slough near the Southern Pacific Railroad bridge, eastward to the Yolo Bypass.
Environmental Conditions: |
QAPP Information: | Data quality: Questionable. Monitoring was conducted in accordance with the Quality Assurance Project Plan For Water Quality Monitoring For The Yolo Bypass Watershed Planning Project, 2003-2004
QAPP Information Reference(s):

DECISION ID | 11485
Pollutant: | Escherichia coli (E. Coli)
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 | Source Unknown
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 3.2 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. Eleven 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. Eleven of 13 samples exceeded the E. Coli objective and this exceeds the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
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 11485

LOE ID: | 23279
Pollutant: | Escherichia coli (E. Coli)
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | None
Beneficial Use: | Water Contact Recreation
Number of Samples: | 13
Number of Exceedances: | 11
Data and Information Type: | PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: | The Yolo Bypass Watershed Planning Program collected 13 samples from November 2003 to October 2004. Eleven of the 13 samples exceeded the evaluation objective.
Data Reference: | Yolo Bypass Water Quality Management Plan Report. Prepared under CALFED Watershed Grant, Agreement # 4600001691 for the City of Woodland
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. The objective applies regardless of whether the toxicity is caused by a single substance or the interactive effect of multiple substances.
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: | In waters designated for contact recreation (REC-1), the E. coli concentration, based on a minimum of not less than five samples equally spaced over a 30-day period, shall not exceed a geometric mean of 126 MPN/100 mL and shall not exceed 235 MPN /100 mL in any single sample.
Guideline Reference: | Ambient Water Quality Criteria for Bacteria - 1986. EPA440/5-84-002
Spatial Representation: | Samples were collected from Willow Slough.
Temporal Representation: | Sampling occurred from November 2003 to October 2004.
Environmental Conditions: |
QAPP Information: | Data quality: Good. Monitoring was conducted in accordance with the Quality Assurance Project Plan For Water Quality Monitoring For The Yolo Bypass Watershed Planning Project, 2003-2004
QAPP Information Reference(s):

DECISION ID | 11486
Pollutant: | Fecal Coliform
Final Listing Decision: | List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision: | New Decision
Revision Status | Revised
Sources: | Source Unknown
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 3.2 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. Ten 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. Ten of 12 calculated geometric means exceeded the fecal coliform objective and this exceeds the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
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 11486

LOE ID: | 23265
Pollutant: | Fecal Coliform
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | None
Beneficial Use: | Water Contact Recreation
Number of Samples: | 12
Number of Exceedances: | 10
Data and Information Type: | PATHOGEN MONITORING
Data Used to Assess Water Quality: | The Yolo Bypass Watershed Planning Program collected 10 samples from November 2003 to October 2004. The geometric mean per month per site was calculated from the samples and 10 out of the 12 calculated geometric means exceeded the evaluation objective.
Data Reference: | Yolo Bypass Water Quality Management Plan Report. Prepared under CALFED Watershed Grant, Agreement # 4600001691 for the City of Woodland
Water Quality Objective/Criterion: | In waters designated for contact recreation (REC-1), the fecal coliform concentration based on a minimum of not less than five samples for any 30-day period shall not exceed a geometric mean of 200/100 ml, nor shall more than ten percent of the total number of samples taken during any 30-day period exceed 400/100 ml.
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 Bypass.
Temporal Representation: | Sampling occurred from November 2003 to October 2004
Environmental Conditions: |
QAPP Information: | Data quality: Good. Monitoring was conducted in accordance with the Quality Assurance Project Plan For Water Quality Monitoring For The Yolo Bypass Watershed Planning Project, 2003-2004
QAPP Information Reference(s):