| Water Body Name: | Arroyo Sequit (from confluence of East and West Forks to mouth) |
| Water Body ID: | CAR4044400020110630163301 |
| Water Body Type: | River & Stream |
DECISION ID |
98573 |
Region 4 |
Arroyo Sequit (from confluence of East and West Forks to mouth) |
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| Pollutant: | Benthic Community Effects |
| Final Listing Decision: | Do Not List on 303(d) list (TMDL required list) |
| Last Listing Cycle's Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)(2016) |
| Revision Status | Original |
| Impairment from Pollutant or Pollution: | Pollutant |
| Regional Board Conclusion: | Benthic Community Effects is being considered for placement on the CWA section 303(d) List under section 3.9 of the Listing Policy.
1 line of evidence is available in the administrative record to assess this pollutant. 0 of 3 samples exceeded the GUIDELINE. Based on the readily available data and information, the weight of evidence indicates that there is insufficient justification for placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 3 samples were below the California Stream Condition Index (CSCI) score of 0.79, indicating good benthic invertebrate community composition for this area and good water quality. This does not meet the requirements of section 3.9 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. The CSCI is applicable statewide, accounts for a much wider range of natural variability, and provides equivalent scoring thresholds in all regions of the state. The CSCI will be used in the future for water quality assessment purposes statewide over the regional indices of biologic integrity (IBIs). |
| Regional Board Decision Recommendation: | After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded. |
| State Board Review of Regional Board Conclusion and Recommendation: | The CSCI is applicable statewide, accounts for a much wider range of natural variability, and provides equivalent scoring thresholds in all regions of the state. The CSCI will be used in the future for water quality assessment purposes statewide over the regional indices of biologic integrity (IBIs). |
| State Board Decision Recommendation: | After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board. |
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| LOE ID: | 82892 | ||||
| Pollutant: | Benthic-Macroinvertebrate Bioassessments | ||||
| LOE Subgroup: | Population/Community Degradation | ||||
| Matrix: | Water | ||||
| Fraction: | Not Recorded | ||||
| Beneficial Use: | Warm Freshwater Habitat | ||||
| Number of Samples: | 3 | ||||
| Number of Exceedances: | 0 | ||||
| Data and Information Type: | Benthic macroinvertebrate surveys | ||||
| Data Used to Assess Water Quality: | None of the three samples collected had an IBI score below 40. The scores at site AS19 were 57 (fall 2006), 49 (spring 2008) and 70 (spring 2009). | ||||
| Data Reference: | Data for abundance calculations, taxa list and IBI scores in Malibu Creek Watershed, 2006-2009. | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | All waters shall be maintained free of toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in, human, plant or animal, or aquatic life. Compliance with this objective will be determined by use of indicator organisms, analysis of species diversity, population density, growth anomalies, bioassays of appropriate duration or other appropriate methods as specified by the State or Regional Board. Region 4 Basin Plan. | ||||
| Objective/Criterion Reference: | Water Quality Control Plan Los Angeles Region R4 Basin Plan | ||||
| Evaluation Guideline: | The IBI is a multi-metric assessment that employs biological metrics that respond to a habitat or water quality impairment. Each of the biological metrics measured at a site are converted to an IBI score then summed. These cumulative scores are then ranked. For the Southern California IBI, sites with scores below 40 are considered to have impaired conditions. | ||||
| Guideline Reference: | Development of a Benthic Index of Biotic Integrity (B-IBI) for Wadeable Streams in Northern Coastal California and its Application to Regional 305(b) Assessment | ||||
| Spatial Representation: | The samples were collected at stations AS19 Arroyo Sequit. | ||||
| Temporal Representation: | The samples were collected in the fall 2006 and spring 2008 and 2009. | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Data was collected in compliance with California Stream Bioassessment Procedure. Collection procedures were audited by California Department of Fish and Game in 2006. | ||||
| QAPP Information Reference(s): | |||||
DECISION ID |
92673 |
Region 4 |
Arroyo Sequit (from confluence of East and West Forks to mouth) |
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| Pollutant: | Oxygen, Dissolved |
| Final Listing Decision: | Do Not List on 303(d) list (TMDL required list) |
| Last Listing Cycle's Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)(2016) |
| Revision Status | Original |
| Impairment from Pollutant or Pollution: | Pollutant |
| Regional Board Conclusion: | This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence are necessary to assess listing status.
1 line of evidence is available in the administrative record to assess this pollutant. 0 of 4 samples exceeded the OBJECTIVE. Based on the readily available data and information, the weight of evidence indicates that there is insufficient justification for placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 4 samples exceeded the OBJECTIVE and this sample size is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. A minimum of 26 samples is needed to determine if a beneficial use is fully supported using table 3.2. 4. Pursuant to SECTION 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met. |
| Regional Board Decision Recommendation: | After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. |
| State Board Review of Regional Board Conclusion and Recommendation: | |
| State Board Decision Recommendation: | After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board. |
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| LOE ID: | 82893 | ||||
| Pollutant: | Oxygen, Dissolved | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | Dissolved | ||||
| Beneficial Use: | Warm Freshwater Habitat | ||||
| Number of Samples: | 4 | ||||
| Number of Exceedances: | 0 | ||||
| Data and Information Type: | PHYSICAL/CHEMICAL MONITORING | ||||
| Data Used to Assess Water Quality: | Numeric data generated from 4 minimums of Dissolved Oxygen concentrations had no exceedences. | ||||
| Data Reference: | Data for Metals, Nuisance, Nutrients, Other Inorganics, and Salinity in Various Region 4 Water Bodies, 2006-2010. | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | Dissolved Oxygen Water Quality Objective of all surface waters designated as Warm Fresh Water Aquatic Habitat shall not be depressed below 5 mg/l. | ||||
| Objective/Criterion Reference: | Water Quality Control Plan Los Angeles Region R4 Basin Plan | ||||
| Evaluation Guideline: | |||||
| Guideline Reference: | |||||
| Spatial Representation: | Samples were collected from the J_ARRSEQ station. | ||||
| Temporal Representation: | Samples were collected approximately semi-annually from August 2006 to December 2008. | ||||
| Environmental Conditions: | |||||
| QAPP Information: | NPDES quality assurance. | ||||
| QAPP Information Reference(s): | |||||
DECISION ID |
92672 |
Region 4 |
Arroyo Sequit (from confluence of East and West Forks to mouth) |
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| Pollutant: | pH |
| Final Listing Decision: | Do Not List on 303(d) list (TMDL required list) |
| Last Listing Cycle's Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)(2016) |
| Revision Status | Original |
| Impairment from Pollutant or Pollution: | Pollutant |
| Regional Board Conclusion: | This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence are necessary to assess listing status.
1 line of evidence is available in the administrative record to assess this pollutant. 1 of 4 samples exceeded the OBJECTIVE. Based on the readily available data and information, the weight of evidence indicates that there is insufficient justification for placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 1 of 4 samples exceeded the OBJECTIVE and this sample size is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. A minimum of 26 samples is needed to determine if a beneficial use is fully supported using table 3.2. 4. Pursuant to SECTION 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met. |
| Regional Board Decision Recommendation: | After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. |
| State Board Review of Regional Board Conclusion and Recommendation: | |
| State Board Decision Recommendation: | After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board. |
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| LOE ID: | 82894 | ||||
| Pollutant: | pH | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | Dissolved | ||||
| Beneficial Use: | Warm Freshwater Habitat | ||||
| Number of Samples: | 4 | ||||
| Number of Exceedances: | 1 | ||||
| Data and Information Type: | PHYSICAL/CHEMICAL MONITORING | ||||
| Data Used to Assess Water Quality: | One of 4 samples exceeded the objective. | ||||
| Data Reference: | Data for Metals, Nuisance, Nutrients, Other Inorganics, and Salinity in Various Region 4 Water Bodies, 2006-2010. | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | The pH of all inland surface waters shall not be depressed below 6.5 or raised above 8.5 as a result of waste discharges. | ||||
| Objective/Criterion Reference: | Water Quality Control Plan Los Angeles Region R4 Basin Plan | ||||
| Evaluation Guideline: | |||||
| Guideline Reference: | |||||
| Spatial Representation: | Samples were collected from the J_ARRSEQ station. | ||||
| Temporal Representation: | Samples were collected approximately semi-annually from October 2006 to December 2008 | ||||
| Environmental Conditions: | |||||
| QAPP Information: | NPDES quality assurance. | ||||
| QAPP Information Reference(s): | |||||