San Diego Region - Rainbow Creek Total Nitrogen and Total Phosphorus TMDLs


The California Regional Water Quality Control Board, San Diego Region (Regional Board) has adopted Total Maximum Daily Loads (TMDLs) for Total Nitrogen and Total Phosphorus to address water quality impairments in Rainbow Creek. A TMDL allocates pollution control responsibilities among pollution sources in a watershed, and is the basis for taking the actions needed to restore a water body.

Rainbow Creek was placed on the 303(d) list of "water quality limited" water bodies in 1996 because data indicated that beneficial uses in the creek were impaired. Nutrient concentrations in Rainbow Creek did not meet the objective for nitrates in a municipal supply or the numeric goals for biostimulatory substances (total nitrogen and total phosphorus) contained in the San Diego Regional Water Quality Control Board, Water Quality Control Plan for the San Diego Basin (9) (Basin Plan). Elevated nutrient concentrations have caused excessive algal growth in portions of the creek.

On February 9, 2005, the Regional Board conducted a public hearing and adopted the amendment to the Basin Plan to include the Total Nitrogen and Total Phosphorus TMDLs and implementation plan. The State Water Resources Control Board, on November 16, 2005, and Office of Administrative Law, on February 1, 2006, subsequently approved the Basin Plan amendment. The U.S. Environmental Protection Agency granted final approval of the TMDLs on March 22, 2006.

Public Documents

Documents associated with the adoption of this TMDL are available for review at the San Diego Water Board Office. To request a file review please contact the Regional Board receptionist at (619) 516-1990, or email

Rainbow Creek Nutrient TMDLs Transfer Plan

Resolution No. R9-2005-0036

  • Attachment A – Basin Plan Amendment

Final Technical Report for Rainbow Creek TMDL Appendices

Please contact Ms. Cynthia Gorham at 619-521-3921, or by email at