Cal. Code Regs. tit. 23 § 3989.3
Regional Board Resolution No. R9-2005-0036, adopted on February 9, 2005 by the San Diego Regional Water Quality Control Board, modified the regulatory provisions of the Water Quality Control Plan for the San Diego Region by (1) adding a footnote to Chapter 2 (Beneficial Uses) referencing Rainbow Creek's listing on the Clean Water Act Section 303(d) list, (2) adding text to Chapter 3 (Water Quality Objectives) referencing the 303(d) listing of Rainbow Creek and adoption of the TMDLs implementation plans in Chapter 4 (Implementation), and (3) adding text to Chapter 4 establishing total nitrogen and total phosphorus total maximum daily loads (TMDLs) for Rainbow Creek Watershed.
The TMDLs address impairment due to excess nutrients being discharged to the creek from land uses, including agricultural and residential uses, highway runoff, and contaminated groundwater. The numeric targets limit concentrations of nitrate to protect drinking water resources, and total nitrogen and total phosphorus to prevent the development of excessive algae that can lead to eutrophic conditions in Rainbow Creek. Compliance with objectives to protect municipal supply, water contact and non-water contact recreation, and aquatic and wildlife beneficial uses is to be achieved no later than 16 years after U.S. Environmental Protection Agency approval of the TMDLs. Load allocations are assigned for land uses, septic tank disposal systems, and air deposition. Waste load allocations are assigned for highway runoff and unidentified point sources. Reductions will be phased over the compliance period. Implementation includes investigations of groundwater contamination, water quality monitoring, and implementation of best management practices to control runoff. Additional regulatory enforcement options are to be used if necessary. The total nitrogen and total phosphorus TMDLs contain a five percent (5%) explicit margin of safety.
Cal. Code Regs. Tit. 23, § 3989.3