Cal. Code Regs. tit. 23 § 3989.8
Through Regional Water Board Resolution R9-2008-0028, adopted on May 14, 2008, the San Diego Regional Water Quality Control Board amended the Water Quality Control Plan for the San Diego Region (Basin Plan). On March 17, 2009, the State Water Resources Control Board (State Water Board) approved this amendment under Resolution No. 2009-0030. This Basin Plan amendment incorporates implementation provisions for indicator bacteria water quality objectives to account for loading from natural uncontrollable sources using either a reference system antidegradation approach, or a natural source exclusion approach within the context of a TMDL. The reference system antidegradation approach or natural source exclusion approach only apply to municipal separate storm sewer system (MS4), concentrated animal feeding operations, and nonpoint source discharges. Furthermore, these approaches apply only during the development and implementation of indicator bacteria TMDLs.
Cal. Code Regs. Tit. 23, § 3989.8