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.

The staff report, titled "Basin Plan Amendment and Technical Report for Total Nitrogen and Total Phosphorus Total Maximum Daily Loads for Rainbow Creek", includes a problem statement, numeric targets, source analysis, load allocations, linkage between numeric targets and pollutants, a margin of safety, a discussion of seasonal variation and critical conditions, and an implementation plan and monitoring strategy. The staff report also addresses CEQA requirements (including the Environmental Checklist and Draft Certificate of Fee Exemption) and economic considerations.

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

(All Documents are in PDF format unless otherwise noted)

Date Posted Description

RainbowCreek Nutrient TMDLs Transfer Plan

Final Documents
Final Technical Report and Appendices for the Rainbow Creek TMDL

San Diego Regional Board Hearing - February 9, 2005.

Comment letters from:
Rainbow Creek Board Hearing Presentation on December 08, 2004.
November 17, 2004 Public Workshop

Documents related to November 17th, 2004 Workshop and December 8th, 2004 Public Hearing.

Public Notice for Workshop and Public Hearing

Documents related to May 8, 2002 Public Hearing

Notice of Public Hearing - Basin Plan Amendment to include Rainbow Creek Nutrient TMDLs
Draft Resolution No. R9-2002-0108
Draft Basin Plan Amendment
Staff Report for Nutrient TMDLs for Rainbow Creek
Attachment A - Figures
Attachment B - Tables
Attachment C - Photos
Attachment D - List of Events
Attachment E - Environmental Checklist
Attachment F - Scientific Peer Review
Attachment G - Response to Peer Review Comments

Map of Rainbow Creek Watershed - (in JPG format)

For Additional Information

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