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

Supporting Information

Regional Board 2 - San Francisco Bay Region

Water Body Name: San Mateo Creek, Lower
Water Body ID: CAR2044003320090202015405
Water Body Type: River & Stream
 
DECISION ID
17662
 
Pollutant: Arsenic | Chromium (total) | Copper | Lead | Nickel | Silver | Zinc
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 lines 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 three samples exceeded the water quality guidelines 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, Water Board 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 17662
 
LOE ID: 28854
 
Pollutant: Arsenic | Chromium (total) | Copper | Lead | Nickel | Silver | Zinc
LOE Subgroup: Pollutant-Water
Matrix: Water
Fraction: Dissolved
 
Beneficial Use: Cold Freshwater Habitat
 
Number of Samples: 3
Number of Exceedances: 0
 
Data and Information Type: PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: The San Mateo Creek watershed was monitored as part of SWAMP assessment. None of the three samples exceeded the water quality objectives for arsenic, chromium VI, copper, lead, nickel, silver and zinc.
Concentrations of total dissolved chromium were well below the objective for chromium VI.
Data Reference: Water Quality Monitoring and Bioassessment in Four San Francisco Bay Region Watersheds in 2003-2004: Kirker Creek, Mt. Diablo Creek, Petaluma River, and San Mateo Creek. Surface Water Monitoring Program, San Francisco Bay Regional Water Quality Control Board, Oakland. CA
 
Water Quality Objective/Criterion: All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: arsenic- 150 ug/L, chromium VI- 11 ug/L, copper - 9.0 ug/L, lead - 2.5 ug/L; nickel - 52 ug/L, silver-3.4 ug/L and zinc - 120 ug/L.
Objective/Criterion Reference: San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan)
 
Evaluation Guideline:
Guideline Reference:
 
Spatial Representation: Data were collected at one most downstream sampling location in San Mateo Creek - SMA020 (Gateway Park).
Temporal Representation: Samples were collected locations during wet, spring and dry seasons of the 2003-2004 sampling season.
Environmental Conditions:
QAPP Information: All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
QAPP Information Reference(s): Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)
 
DECISION ID
17663
 
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 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 three samples exceeded the water quality guidelines and 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, Water Boards 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.
 
SWRCB Board Decision / Staff Recommendation:
 
USEPA Decision:
 
 
Lines of Evidence (LOEs) for Decision ID 17663
 
LOE ID: 29025
 
Pollutant: Chlorpyrifos
LOE Subgroup: Pollutant-Water
Matrix: Water
Fraction: None
 
Beneficial Use: Warm Freshwater Habitat
 
Number of Samples: 3
Number of Exceedances: 1
 
Data and Information Type: PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: The San Mateo Creek watershed was monitored as part of SWAMP assessment. One of the three samples exceeded the water quality objective for chlorpyrifos with a sample concentration of 0.0751 ug/L.
Data Reference: Water Quality Monitoring and Bioassessment in Four San Francisco Bay Region Watersheds in 2003-2004: Kirker Creek, Mt. Diablo Creek, Petaluma River, and San Mateo Creek. Surface Water Monitoring Program, San Francisco Bay Regional Water Quality Control Board, Oakland. CA
 
Water Quality Objective/Criterion: All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
Table 3-4 in the Basin Plan (2007) lists freshwater water quality objectives for toxic pollutants: Chlorpyrifos - 0.015 ug/L (chronic).
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
  San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan)
  Central Valley Regional Water Quality Control Board. Water Quality Control Plan (Basin Plan) for the California Regional Water Quality Control Board - Central Valley Region
  Hazard Assessment of the Insecticide Methyl Parathion to Aquatic Organisms in the Sacramento River System. California Department of Fish and Game. Environmental Services Division. Administrative Report 92-1
  Hazard Assessment of the Rice Herbicides Molinate and Thiobencarb to Aquatic Organisms in the Sacramento River System. Administrative Report 90-1. California Department of Fish and Game, Environmental Services Division
 
Evaluation Guideline:
Guideline Reference:
 
Spatial Representation: Data were collected at one sampling location: SMA020 (Gateway Park).
Temporal Representation: Samples were collected during winter (January), spring (April), and dry (June) seasons of 2003.
Environmental Conditions:
QAPP Information: All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
QAPP Information Reference(s): Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)
 
DECISION ID
17664
 
Pollutant: Chromium (total)
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 3.1of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status.

One line of evidence is available in the administrative record to assess this pollutant. 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 one sample exceeded the water quality guidelines and 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, Water Boards 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.
 
SWRCB Board Decision / Staff Recommendation:
 
USEPA Decision:
 
 
Lines of Evidence (LOEs) for Decision ID 17664
 
LOE ID: 28767
 
Pollutant: Chromium (total)
LOE Subgroup: Pollutant-Sediment
Matrix: Sediment
Fraction: Total
 
Beneficial Use: Cold Freshwater Habitat
 
Number of Samples: 1
Number of Exceedances: 1
 
Data and Information Type: PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: Chromium exceeded the PEC level with a sample concentration of 183 mg/kg dw in one sediment sample collected in spring 2003 (sediment quality guidelines).
Data Reference: Water Quality Monitoring and Bioassessment in Four San Francisco Bay Region Watersheds in 2003-2004: Kirker Creek, Mt. Diablo Creek, Petaluma River, and San Mateo Creek. Surface Water Monitoring Program, San Francisco Bay Regional Water Quality Control Board, Oakland. CA
 
Water Quality Objective/Criterion: All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
Objective/Criterion Reference: San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan)
 
Evaluation Guideline: Sediment Quality Guidelines (MacDonald et al., 2000): PEC (probable effect concentration) chromium - 111 mg/kg dw.
Guideline Reference: Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Environmental Contamination and Toxicology. 39: 20-31
 
Spatial Representation: One sediment sample was collected at a "watershed integrator" site located close to the mouth of San Mateo Creek.
Temporal Representation: Sediment sample was collected in April of 2003.
Environmental Conditions:
QAPP Information: All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
QAPP Information Reference(s):
 
DECISION ID
17665
 
Pollutant: Dacthal | Disulfoton | Endosulfan | Lindane/gamma Hexachlorocyclohexane (gamma-HCH) | Methyl Parathion | PCBs (Polychlorinated biphenyls) | Thiobencarb/Bolero
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 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 three samples exceeded the water quality guidelines 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, Water Boards 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 17665
 
LOE ID: 29024
 
Pollutant: Dacthal | Disulfoton | Endosulfan | Lindane/gamma Hexachlorocyclohexane (gamma-HCH) | Methyl Parathion | PCBs (Polychlorinated biphenyls) | Thiobencarb/Bolero
LOE Subgroup: Pollutant-Water
Matrix: Water
Fraction: None
 
Beneficial Use: Warm Freshwater Habitat
 
Number of Samples: 3
Number of Exceedances: 0
 
Data and Information Type: PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: The San Mateo Creek watershed was monitored as part of SWAMP assessment. None of the three samples exceeded the water quality objectives for PCBs, Dacthal, disulfoton, endosulfan, Lindane/gamma Hexachlorocyclohexane (gamma-HCH), methyl parathion, thiobencarb.
Data Reference: Water Quality Monitoring and Bioassessment in Four San Francisco Bay Region Watersheds in 2003-2004: Kirker Creek, Mt. Diablo Creek, Petaluma River, and San Mateo Creek. Surface Water Monitoring Program, San Francisco Bay Regional Water Quality Control Board, Oakland. CA
 
Water Quality Objective/Criterion: All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.
Objective/Criterion Reference: San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan)
 
Evaluation Guideline: PCBs - 0.014 ug/L freshwater continuous Concentration; Chlorpyrifos - 0.015 ug/L (chronic); Dacthal (DCPA) - 14300 ug/L (acute); Disulfoton (Disyston) - 0.05 ug/L (acute); Endosulfan - 0.056 ug/L (chronic)/0.22 ug/L (acute); HCH, gamma-(gamma BHC, Lindane) - 0.95 ug/L (acute); methyl parathion - 0.08 ug/L (acute); Thiobencarb - 3.1 ug/L (acute).
Guideline Reference: National recommended water quality criteria: 2002. EPA-822-R-02-047 Washington, D.C. USEPA
 
Spatial Representation: Data were collected at one sampling location: SMA020 (Gateway Park).
Temporal Representation: Samples were collected during winter (January), spring (April), and one dry (June) seasons of 2003.
Environmental Conditions:
QAPP Information: All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
QAPP Information Reference(s): Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)
 
DECISION ID
17470
 
Pollutant: Escherichia coli (E. Coli)
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 3.3 of the Listing Policy. Under section 3.3 a single line of evidence is necessary to assess listing status.

One line of evidence is available in the administrative record to assess this pollutant. Three out of three 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. Three of three samples exceeded the number of Escherichia coli (E. Coli) counts 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, Water Board 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 being exceeded.
 
SWRCB Board Decision / Staff Recommendation:
 
USEPA Decision:
 
 
Lines of Evidence (LOEs) for Decision ID 17470
 
LOE ID: 29018
 
Pollutant: Escherichia coli (E. Coli)
LOE Subgroup: Pollutant-Water
Matrix: Water
Fraction: None
 
Beneficial Use: Non-Contact Recreation
 
Number of Samples: 3
Number of Exceedances: 3
 
Data and Information Type: PATHOGEN MONITORING
Data Used to Assess Water Quality: Samples were collected as part of SWAMP sampling in the summer of 2003 at 7-day intervals and the geometric mean of the samples calculated over a five week interval. Samples were collected at three locations: SMA020, SMA060, and SMA080. The geometric mean for SMA020 was 403 MPN/100 mL, for SMA060 was 1234 MPN/100 mL, and for SMA080 was 1668 MPN/100 mL, all exceed the 126 MPN/100ml criteria.
Data Reference: Water Quality Monitoring and Bioassessment in Four San Francisco Bay Region Watersheds in 2003-2004: Kirker Creek, Mt. Diablo Creek, Petaluma River, and San Mateo Creek. Surface Water Monitoring Program, San Francisco Bay Regional Water Quality Control Board, Oakland. CA
 
Water Quality Objective/Criterion: Uses of water for recreational activities involving body contact with water where ingestion of water is reasonably possible. These uses include, but are not limited to, swimming, wading, water-skiing, skin and scuba diving, surfing, whitewater activities, fishing, and uses of natural hot springs.

Water contact implies a risk of waterborne disease transmission and involves human health; accordingly, criteria required to protect this use are more stringent than those for more casual water-oriented recreation.
U.S. EPA water quality criteria for water contact recreation based on the frequency of use a particular area receives - 1986: the E. coli criterion is not to exceed 126 organisms/100 mL. The value is expressed as a 7-day geometric mean based on five or more samples per 30–day period; designated beach (max) 235 MPN/100 mL.
Objective/Criterion Reference: San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan)
  Ambient Water Quality Criteria for Bacteria - 1986. EPA440/5-84-002
 
Evaluation Guideline:
Guideline Reference:
 
Spatial Representation: Samples were collected at SMA020 (Gateway Park), SMA060 (Arroyo Court Park), and SMA080 (Sierra Drive).
Temporal Representation: Samples were collected weekly from 7/21/2003 through 8/18/2003.
Environmental Conditions:
QAPP Information: All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
QAPP Information Reference(s): Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)
 
DECISION ID
17666
 
Pollutant: Nickel
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 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 one sample exceeded the water quality guidelines and 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, Water Boards 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.
 
SWRCB Board Decision / Staff Recommendation:
 
USEPA Decision:
 
 
Lines of Evidence (LOEs) for Decision ID 17666
 
LOE ID: 28766
 
Pollutant: Nickel
LOE Subgroup: Pollutant-Sediment
Matrix: Sediment
Fraction: Total
 
Beneficial Use: Cold Freshwater Habitat
 
Number of Samples: 1
Number of Exceedances: 1
 
Data and Information Type: PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: Nickel exceeded the PEC level with a sample concentration of 188 mg/kg dw in one sediment sample collected in spring 2003 (sediment quality guidelines).
Data Reference: Water Quality Monitoring and Bioassessment in Four San Francisco Bay Region Watersheds in 2003-2004: Kirker Creek, Mt. Diablo Creek, Petaluma River, and San Mateo Creek. Surface Water Monitoring Program, San Francisco Bay Regional Water Quality Control Board, Oakland. CA
 
Water Quality Objective/Criterion: All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
Objective/Criterion Reference: San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan)
 
Evaluation Guideline: Sediment Quality Guidelines (MacDonald et al., 2000): PEC (threshold effect concentration) nickel - 48.6 mg/kg dw.
Guideline Reference: Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Environmental Contamination and Toxicology. 39: 20-31
 
Spatial Representation: One sediment sample was collected at a "watershed integrator" site located close to the mouth of San Mateo Creek.
Temporal Representation: Sediment sample was collected in April of 2003.
Environmental Conditions:
QAPP Information: All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
QAPP Information Reference(s):
 
DECISION ID
17675
 
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.

Two lines of evidence are available in the administrative record to assess this pollutant. Four 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. Four of fourteen samples exceeded the water quality guidelines and this sample size is insufficient to determine with the power and confidence of the Listing Policy if standards are not met. A minimum of five samples is needed for application of table 3.2.
4. Pursuant to SECTION 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
 
RWQCB Board Decision / Staff Recommendation: After review of the available data and information, Water Board staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because there is insufficient information to determine that the standards are not met.
 
SWRCB Board Decision / Staff Recommendation:
 
USEPA Decision:
 
 
Lines of Evidence (LOEs) for Decision ID 17675
 
LOE ID: 28623
 
Pollutant: Oxygen, Dissolved
LOE Subgroup: Pollutant-Water
Matrix: Water
Fraction: None
 
Beneficial Use: Cold Freshwater Habitat
 
Number of Samples: 14
Number of Exceedances: 4
 
Data and Information Type: PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: Comprehensive water quality assessment was conducted at San Mateo Creek watershed as part of SWAMP assessment in 2003 and 2004. Continuous field monitoring of temperature, dissolved oxygen, pH, and specific conductance to determine temporal variability in basic water quality at one or two locations. The 7 day average minimum concentration of dissolved oxygen ranged from 0.86 to 12.09 mg/L and varied with season. Minimum dissolved oxygen levels fell below the objective of 7 mg/L at one location in spring (March 2003), two in the summer (August 2003) and one in the fall (October 2003) sampling events. The 7 day average concentration levels were 1.0, 0.86, 6.10, and 2.69 mg/L DO, respectively, at the lower monitoring sites.
Data Reference: Water Quality Monitoring and Bioassessment in Four San Francisco Bay Region Watersheds in 2003-2004: Kirker Creek, Mt. Diablo Creek, Petaluma River, and San Mateo Creek. Surface Water Monitoring Program, San Francisco Bay Regional Water Quality Control Board, Oakland. CA
 
Water Quality Objective/Criterion: The numeric water quality objective for dissolved oxygen is 7.0 mg/L minimum for waters designated as cold water habitat. The median dissolved oxygen concentration for any three consecutive months shall not be less than 80 percent of the dissolved oxygen content at saturation.
Objective/Criterion Reference: San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan)
 
Evaluation Guideline:
Guideline Reference:
 
Spatial Representation: Dissolved oxygen was measured at three sites ( SMA020, SMA060, and SMA120) located on the mainstem of San Mateo Creek Lower and one site (SMA110) located at the confluence of Polhemus Creek and San Mateo Creek.
Temporal Representation: At all locations the SWAMP performed continuous monitoring of dissolved oxygen at 15 minute intervals lasting 7-20 days during spring (March 2003), summer and fall dry season (July and October 2003), and winter wet season (February 2004).
Environmental Conditions:
QAPP Information: All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
QAPP Information Reference(s):
 
LOE ID: 28621
 
Pollutant: Oxygen, Dissolved
LOE Subgroup: Pollutant-Water
Matrix: Water
Fraction: None
 
Beneficial Use: Warm Freshwater Habitat
 
Number of Samples: 14
Number of Exceedances: 3
 
Data and Information Type: PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: Comprehensive water quality assessment was conducted at San Mateo Creek watershed as part of SWAMP assessment in 2003 and 2004. Continuous field monitoring of temperature, dissolved oxygen, pH, and specific conductance to determine temporal variability in basic water quality at one or two locations. The 7 day average minimum concentration of dissolved oxygen ranged from 0.86 to 12.09 mg/L and varied with season. Minimum dissolved oxygen levels fell below the objective of 5 mg/L at one location each in spring (March 2003), the summer (August 2003) and the fall (October 2003) sampling events. The 7 day average concentration levels were 1.0, 0.86, and 2.69 mg/L DO, respectively, at the lower monitoring sites.
Data Reference: Water Quality Monitoring and Bioassessment in Four San Francisco Bay Region Watersheds in 2003-2004: Kirker Creek, Mt. Diablo Creek, Petaluma River, and San Mateo Creek. Surface Water Monitoring Program, San Francisco Bay Regional Water Quality Control Board, Oakland. CA
 
Water Quality Objective/Criterion: The numeric water quality objective for dissolved oxygen is 5.0 mg/L minimum for waters designated as warm water habitat. The median dissolved oxygen concentration for any three consecutive months shall not be less than 80 percent of the dissolved oxygen content at saturation.
Objective/Criterion Reference: San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan)
 
Evaluation Guideline:
Guideline Reference:
 
Spatial Representation: Dissolved oxygen was measured at three sites (SMA020, SMA060, and SMA120) located on the mainstem of San Mateo Creek Lower and one site (SMA110) located at the confluence of Polhemus Creek and San Mateo Creek.
Temporal Representation: At all locations the SWAMP performed continuous monitoring of dissolved oxygen at 15 minute intervals lasting 7-20 days during spring (March 2003), summer and fall dry seasons (July, October 2003), and winter wet season (February 2004).
Environmental Conditions:
QAPP Information: All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
QAPP Information Reference(s):
 
DECISION ID
17667
 
Pollutant: Temperature, water
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 lines of evidence are available in the administrative record to assess this pollutant. Three 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. Three of fifteen samples exceeded the water quality guidelines and this sample size is insufficient to determine with the power and confidence of the Listing Policy if standards are not met. A minimum of five samples is needed for application of table 3.2.
4. Pursuant to SECTION 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
 
RWQCB Board Decision / Staff Recommendation: After review of the available data and information, Water Boards 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.
 
SWRCB Board Decision / Staff Recommendation:
 
USEPA Decision:
 
 
Lines of Evidence (LOEs) for Decision ID 17667
 
LOE ID: 29030
 
Pollutant: Temperature, water
LOE Subgroup: Pollutant-Water
Matrix: Water
Fraction: None
 
Beneficial Use: Cold Freshwater Habitat
 
Number of Samples: 15
Number of Exceedances: 3
 
Data and Information Type: PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: Water quality assessment was conducted at the San Mateo Creek watershed as part of SWAMP study in 2003-2004. Continuous field monitoring at 15 minute increments of temperature, dissolved oxygen, pH and specific conductance was conducted to determine temporal variability in basic water quality at three to four locations. Continuous monitoring sondes were deployed 15 times at monitoring locations during wet, spring and two dry seasons. The measured temperatures ranged from 6.76°C to 24.86°C and varied with season. During the three of the four summer season deployments, the 7-day mean temperature threshold for steelhead was exceeded. In total, the 17 °C criterion was exceeded in 3 out of 15 deployments.
Data Reference: Water Quality Monitoring and Bioassessment in Four San Francisco Bay Region Watersheds in 2003-2004: Kirker Creek, Mt. Diablo Creek, Petaluma River, and San Mateo Creek. Surface Water Monitoring Program, San Francisco Bay Regional Water Quality Control Board, Oakland. CA
 
Water Quality Objective/Criterion: Temperature objectives for enclosed bays and estuaries are specified in the "Water Quality Control Plan for Control of Temperature in the Coastal and Interstate Waters and Enclosed Bays of California" including any revisions to the plan. In addition, the following temperature objectives apply to surface waters: The natural receiving water temperature of intrastate waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such an alteration does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.
Objective/Criterion Reference: San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan)
 
Evaluation Guideline: Sullivan et al. (2000) reviewed a wide range of studies incorporating information from laboratory-based research, field observations, and risk assessment approaches and developed criteria for assessing temperature risk to aquatic life. The 7-day mean temperature (maximum value of a 7-day moving average of the daily mean temperature) of 14.8°C was established as the upper threshold criterion for coho salmon and 17.0°C for steelhead trout. The risk assessment approach used by Sullivan et al. (2000) suggests that temperatures exceeding the above thresholds will cause a 10% reduction in average growth compared to optimal conditions.
Guideline Reference: An Analysis of the Effects of Temperature on Salmonids of the Pacific Northwest with Implications for Selecting Temperature Criteria
 
Spatial Representation: Continuous field monitoring at 15 minute increments of temperature was performed at three sites ( SMA020, SMA060, and SMA120) located on the mainstem of San Mateo Creek Lower and one site (SMA110) located at the confluence of Polhemus Creek and San Mateo Creek.
Temporal Representation: At all locations the SWAMP performed continuous monitoring of temperature at 15 minute intervals lasting 1-2 weeks during spring (April 2003), summer and fall dry seasons (August and October 2003), and winter wet season (February 2004).
Environmental Conditions:
QAPP Information: All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
QAPP Information Reference(s): Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)
 
DECISION ID
17668
 
Pollutant: 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 one line of evidence is necessary to assess listing status.

One line 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 three samples exceeded the water quality guidelines and 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, Water Boards 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.
 
SWRCB Board Decision / Staff Recommendation:
 
USEPA Decision:
 
 
Lines of Evidence (LOEs) for Decision ID 17668
 
LOE ID: 29029
 
Pollutant: Toxicity
LOE Subgroup: Pollutant-Water
Matrix: Water
Fraction: None
 
Beneficial Use: Cold Freshwater Habitat
 
Number of Samples: 3
Number of Exceedances: 1
 
Data and Information Type: TOXICITY TESTING
Data Used to Assess Water Quality: Three samples were collected in 2003 to evaluate water toxicity at one monitoring location in San Mateo Creek Lower. The toxicity tests included survival and reproduction of Ceriodaphnia, survival and growth of fathead minnow, and growth of Selenastrum.
Statistically significant chronic effects on Pimephales survival was observed in 1 out of 3 samples collected during spring season.
Data Reference: Water Quality Monitoring and Bioassessment in Four San Francisco Bay Region Watersheds in 2003-2004: Kirker Creek, Mt. Diablo Creek, Petaluma River, and San Mateo Creek. Surface Water Monitoring Program, San Francisco Bay Regional Water Quality Control Board, Oakland. CA
 
Water Quality Objective/Criterion: All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.
Objective/Criterion Reference: San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan)
 
Evaluation Guideline: Water toxicity was evaluated according to the SWAMP methodology. The U.S.EPA whole effluent toxicity protocol (U.S.EPA 1994) was used to test the effect of water samples on three freshwater test organisms. Statistical evaluation (alpha = 0.05) and a default threshold of 80% of the control value were used to establish whether water exhibited significant toxicity adversely impacting aquatic organisms.
Guideline Reference: Revised approach to toxicity test acceptability criteria using a statistical performance assessment. Environmental Toxicology and Chemistry, vol. 16, No. 6, pp 1322–1329
  Short-Term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater Organisms. EPA/600/4-91/002. Third Edition. July 1994
 
Spatial Representation: Data were collected at one sampling location, SMA020, on three (3) occasions, representative of the lower reach of the creek.
Temporal Representation: SWAMP samples were collected during winter wet season (January), spring season (April), and dry season (June) of 2003.
Environmental Conditions:
QAPP Information: All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002).
QAPP Information Reference(s): Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)
 
DECISION ID
17674
 
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
 
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 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 fifteen samples exceeded the water quality objectives 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, Water Boards 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 17674
 
LOE ID: 29039
 
Pollutant: pH
LOE Subgroup: Pollutant-Water
Matrix: Water
Fraction: None
 
Beneficial Use: Cold Freshwater Habitat
 
Number of Samples: 15
Number of Exceedances: 1
 
Data and Information Type: PHYSICAL/CHEMICAL MONITORING
Data Used to Assess Water Quality: Comprehensive water quality assessment was conducted at San Mateo Creek watershed as part of SWAMP assessment in 2003 and 2004. Continuous field monitoring of temperature, dissolved oxygen, pH, and specific conductance to determine temporal variability in basic water quality at three to four locations, throughout San Mateo Creek, ranging from 1-15 days. The pH ranged from 7.01 to 8.51 and varied with season. There was one exceedence.
Data Reference: Water Quality Monitoring and Bioassessment in Four San Francisco Bay Region Watersheds in 2003-2004: Kirker Creek, Mt. Diablo Creek, Petaluma River, and San Mateo Creek. Surface Water Monitoring Program, San Francisco Bay Regional Water Quality Control Board, Oakland. CA
 
Water Quality Objective/Criterion: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels.
Objective/Criterion Reference: San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan)
 
Evaluation Guideline:
Guideline Reference:
 
Spatial Representation: pH was measured at three sites ( SMA020, SMA060, and SMA120) located on the mainstem of San Mateo Creek Lower and one site (SMA110) located at the confluence of Polhemus Creek and San Mateo Creek.
Temporal Representation: At all locations the SWAMP performed continuous monitoring of pH at 15 minute intervals lasting 1-15 days during spring (March 2003), summer and fall dry seasons (August and October 2003), and winter wet season (February 2004).
Environmental Conditions:
QAPP Information: All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002)..
QAPP Information Reference(s): Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)
 
DECISION ID
16181
 
Pollutant: Sediment Toxicity
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 listing under section 3.6 of the Listing Policy. Under section 3.6 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. Amphipod toxicity samples exhibit significant toxicity with Hyalella mean survival below 19%.
Based on the readily available data for this water body, the weight of evidence indicates that there is sufficient justification available in favor of adding this water segment-pollutant combination to the section 303(d) list in the Water Quality Limited Segments category.
This conclusion is based on the staff findings that:

1. The data concerning current conditions and supporting the listing decision satisfy the data quality requirements of section 6.1.4 of the Policy.
2. The data used satisfy the data quantity requirements of section 6.1.5 of the Policy.
3. All five sediment samples exhibited significant amphipod toxicity and the benthic community is considered to be degraded. The number of samples with detected significant toxicity 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, Water Board staff concludes that the water body-pollutant combination should be added to 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 16181
 
LOE ID: 26765
 
Pollutant: Sediment Toxicity
LOE Subgroup: Toxicity
Matrix: Sediment
Fraction: None
 
Beneficial Use: Wildlife Habitat
 
Number of Samples: 1
Number of Exceedances: 1
 
Data and Information Type: Toxicity testing of sediments
Data Used to Assess Water Quality: Data used to evaluate sediment toxicity comprise one sediment sample collected by the SWAMP in 2003. The sample was toxic to Hyalella (survival was only 18% of control) in the bulk sediment toxicity test and chronic growth was also significantly affected (28.9% of control).
Comprehensive water quality assessment was conducted at seven monitoring sites in the San Mateo Creek watershed as part of SWAMP assessment. The aim of the monitoring was to determine patterns of water quality, protection of beneficial uses and potential impacts of land use and water management. Sampled parameters included physical and biological indicators, conventional water quality, water metals and toxicity as well as sediment metals and toxicity.
SWAMP sediment sample was collected at the tidally influenced urban segment of San Mateo Creek.
Data Reference: Water Quality Monitoring and Bioassessment in Four San Francisco Bay Region Watersheds in 2003-2004: Kirker Creek, Mt. Diablo Creek, Petaluma River, and San Mateo Creek. Surface Water Monitoring Program, San Francisco Bay Regional Water Quality Control Board, Oakland. CA
 
Water Quality Objective/Criterion: All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.
Objective/Criterion Reference: San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan)
 
Evaluation Guideline: Sediment toxicity data were evaluated according to the SWAMP methodology. Sample toxicity was determined by comparing mean organism response in samples and in negative controls. Statistical evaluation and a default threshold of 80% of the control value were used to establish whether the sediment exhibited significant toxicity adversely impacting aquatic organisms.
Guideline Reference: Revised approach to toxicity test acceptability criteria using a statistical performance assessment. Environmental Toxicology and Chemistry, vol. 16, No. 6, pp 1322–1329
 
Spatial Representation: Data were collected at a sampling location at the lower part of San Mateo Creek within tidal reach.
Temporal Representation: Sample was collected during spring season of 2003.
Environmental Conditions: Data are representative of the lower watershed downstream from Mud Dam with the monitoring site located in the densely urbanized areas.
QAPP Information: Data were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
QAPP Information Reference(s): Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)
 
LOE ID: 26766
 
Pollutant: Sediment Toxicity
LOE Subgroup: Toxicity
Matrix: Sediment
Fraction: None
 
Beneficial Use: Wildlife Habitat
 
Number of Samples: 4
Number of Exceedances: 4
 
Data and Information Type: Toxicity testing of sediments
Data Used to Assess Water Quality: Data used to evaluate sediment toxicity comprise four sediment samples collected as part of a PRISM grant (Lowe et al., 2007) in 2004-2005. All samples were toxic to both freshwater and estuarine amphipods during sampling events and exhibited the lowest per cent survival and highest contaminant concentrations compared to other six tributaries studied.
Data Reference: Final Project Report: Investigations of Sources and Effects of Pyrethroid Pesticides in Watersheds of the San Francisco Bay Estuary. Proposition 13 PRISM Grant # 041355520. SFEI Contribution #523. San Francisco Estuary Institute, Oakland, CA
  Water Quality Monitoring and Bioassessment in Four San Francisco Bay Region Watersheds in 2003-2004: Kirker Creek, Mt. Diablo Creek, Petaluma River, and San Mateo Creek. Surface Water Monitoring Program, San Francisco Bay Regional Water Quality Control Board, Oakland. CA
 
Water Quality Objective/Criterion: All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms.
There shall be no chronic toxicity in ambient waters. Chronic toxicity is a detrimental biological effect on growth rate, reproduction, fertilization success, larval development, population abundance, community composition, or any other relevant measure of the health of an organism, population, or community.
Objective/Criterion Reference: San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan)
 
Evaluation Guideline: Sediment toxicity data were evaluated according to the SWAMP methodology. Sample toxicity was determined by comparing mean organism response in samples and in negative controls. Statistical evaluation and a default threshold of 80% of the control value were used to establish whether the sediment exhibited significant toxicity adversely impacting aquatic organisms.
Guideline Reference: Revised approach to toxicity test acceptability criteria using a statistical performance assessment. Environmental Toxicology and Chemistry, vol. 16, No. 6, pp 1322–1329
 
Spatial Representation: Data were collected at a sampling location at the lower part of San Mateo Creek within tidal reach (2 samples) and at the upper location that at the time of sampling represented the freshwater part of the watershed (2 samples).
Temporal Representation: Samples were collected during winter season of 2004 and late spring of 2005. The winter sampling (November 2004) occurred after the first rain of the season to capture the potential effects of dry season pesticide use. The late spring sampling (April 2005) coincided with the presumption of increased pesticide application in urban and agricultural areas.
Environmental Conditions: Data are representative of the lower watershed downstream from Mud Dam with the monitoring site located in the densely urbanized areas.
QAPP Information: Data were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB 2002).
QAPP Information Reference(s):