| Water Body Name: | Arroyo Seco Reach 3 (above Devils Gate Dam) |
| Water Body ID: | CAR4053200020110720105704 |
| Water Body Type: | River & Stream |
DECISION ID |
97974 |
Region 4 |
Arroyo Seco Reach 3 (above Devils Gate Dam) |
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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: | 82897 | ||||
| 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: | Three samples were collected from Arroyo Seco over three years. None of the three samples collected had an IBI score below 40. The scores were 50 (2006), 40 (2007), and 42 (2008). | ||||
| Data Reference: | Bioassessment Monitoring Report in Los Angeles County, 2006-2008. | ||||
| 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: | A Quantitative Tool for Assessing the Integrity of Southern Coastal California Streams. Environmental Management. Volume 35, number 1 (2005): pp. 1-13 | ||||
| Spatial Representation: | The samples were collected at station 6 Upstream of Arroyo Seco Spreading Grounds. | ||||
| Temporal Representation: | The samples were collected in 2006, 2007 and 2008. | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Los Angeles County Department of Public Works (LACDPW) contracted Weston Solutions, Inc. to perform biological assessments. Sampling and analysis followed the protocols described in the California Stream Bioassessment Procedure (CSBP) (Harrington, 2003),and also incorporated the Southern California Index of Biotic Integrity (IBI) (Ode et al., 2005). | ||||
| QAPP Information Reference(s): | |||||