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

Supporting Information

Regional Board 8 - Santa Ana Region

Water Body Name: Silverado Creek
Water Body ID: CAR8011200019990211132556
Water Body Type: River & Stream
 
DECISION ID
13355
 
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 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status.

One (1) lines of evidence are available in the administrative record to assess this pollutant. Two (2) 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. Two (2) of thirty-four (34) samples exceeded the US EPA Recommended Ambient Water Quality Criteria for Bacteria -1986 and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy.
4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
 
RWQCB Board Decision / Staff Recommendation: After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.
 
SWRCB Board Decision / Staff Recommendation:
 
USEPA Decision:
 
 
Lines of Evidence (LOEs) for Decision ID 13355
 
LOE ID: 21556
 
Pollutant: Escherichia coli (E. Coli)
LOE Subgroup: Pollutant-Water
Matrix: Water
Fraction: None
 
Beneficial Use: Water Contact Recreation
 
Number of Samples: 34
Number of Exceedances: 2
 
Data and Information Type: PATHOGEN MONITORING
Data Used to Assess Water Quality: Of the 34 samples taken, 2 exceeded EPA's Recommended single sample criteria.
Data Reference: Orange County Coast Keeper Coastal Watersheds Project
 
Water Quality Objective/Criterion: USEPA Recommended Ambient Water Quality Criteria for Bacteria -1986: E. coli: log mean less than 126 organisms/100 mL based on five or more samples per 30–day period, and not more than 10% of the samples exceed 235 organisms/100mL for any 30 day period.
Objective/Criterion Reference: Ambient Water Quality Criteria for Bacteria - 1986. EPA440/5-84-002
 
Evaluation Guideline:
Guideline Reference:
 
Spatial Representation: The samples were taken at three locations: Sil1, Sil2, Sil 3.

Sil 1 - Maple Springs is located at the end of the paved section of Silverado Canyon Road just past the National forest gate, down the creek bank to the left. This area is in an area with little foot traffic.

Sil 2 - Smisek: This site is named for the ranch across the street from the creek. The site is easy to find due to the large “Smisek Ranch,” sign overhanging the entrance of the ranch.
Sil 3 - Slide Zone: This site is the lowest site on Silverado Creek at the slide zone signs.
Temporal Representation: The samples were taken monthly starting on November 23, 2002 through June 15, 2004 at Sil 2 and Sil3. The monthly samples at Sil1 were collected starting on December 13, 2002.
Environmental Conditions: Staff is not aware of any special conditions that might effect interpretation of the data.
QAPP Information: The data's quality is deemed appropriate because it was obtained under the auspices of a QAPP approved by the Regional Board.
QAPP Information Reference(s):