Cal. Code Regs. tit. 23 § 3939.26
Resolution No. 2006-022, adopted on November 9, 2006 by the Los Angeles Regional Water Quality Control Board, amended the regulatory provisions of the Water Quality Control Plan for the Los Angeles Region (Basin Plan), by incorporating water-effect ratios (WERs) that modify the copper water quality criteria for Lower Calleguas Creek and Mugu Lagoon in the Calleguas Creek Watershed in Ventura County. The WERs shall be applied as multipliers to the copper water quality criteria contained in the federally promulgated California Toxics Rule (CTR) as set forth in 40 Code of Federal Regulations section 131.38. The WERs modify the current acute (1-hour average) and chronic (4-day average) copper criteria set to protect aquatic life for these waters. The WERs are used to modify the criteria for copper in a manner that considers site-water chemistry, as compared to laboratory water chemistry, to ensure the criteria are as protective of aquatic life as was intended by the CTR. For Mugu Lagoon (Reach 1), the site-specific WER for copper is 1.51. For the Lower Calleguas Creek (Reach 2), the site-specific WER for copper is 3.69. The Basin Plan amendment also specifies water monitoring requirements and other provisions relating to the applicability of the WERs.
Cal. Code Regs. Tit. 23, § 3939.26