Santa Ana Region Total Maximum Daily Loads (TMDLs)

Total Maximum Daily Loads (TMDLs)

The Federal Clean Water Act Section 303(d) requires that States identify waters that do not or are not expected to meet water quality standards (beneficial uses, water quality objectives and the antidegradation policy) with the implementation of technology-based controls. Once a waterbody has been placed on category 5 of the 303(d) list of impaired waters, states are required to develop a Total Maximum Daily Load (TMDL) to address each pollutant causing impairment. A TMDL defines how much of a pollutant a waterbody can tolerate and still meet water quality standards. Each TMDL must account for all sources of the pollutant. TMDLs allocate allowable pollutant loads for each source, and identify management measures that, when implemented, will assure that water quality standards are attained.

More information on the on TMDLs and their development can be found on the State Water Resources Control Board website.

All TMDLs that have been adopted by the Santa Ana Regional Water Quality Control Board and approved by the Environmental Protection Agency (EPA) can be found in Chapter 6 of the Santa Ana Regional Water Quality Control Board’s Water Quality Control Plan (Basin Plan).


Regional Programs Section
Ann Sturdivant
(951) 782-4904

TMDL programs by watershed

Big Bear Lake, located in the San Bernardino Mountains, was created by the construction of the Bear Valley Dam in 1884. The Lake has a surface area of approximately 3,000 acres, a storage capacity of 73,320 acre-ft. and an average depth of 24 feet. The lake reaches its deepest point of 72 feet at the dam. The Big Bear Lake drainage basin encompasses 37 square miles and includes more than 10 streams. A TMDL for Total Phosphorus was adopted for dry hydrological conditions at Big Bear Lake on April 21, 2006. It was then approved by The Office of Administrative Law (OAL) on August 21, 2007 followed by the US Environmental Protection Agency (USEPA) on September 25, 2007. More information including the Implementation Plan can be found in Chapter 6 of the Santa Ana Water Board Basin Plan. Contact: Barbara Barry

The Middle Santa Ana River watershed covers approximately 488 square miles and lies largely in the southwestern corner of San Bernardino County, and the northwestern corner of Riverside County. A small part of Los Angeles County (Pomona/Claremont area) is also included. This watershed is comprised of three sub–watersheds. TMDLs for indicator bacteria were adopted on August 26, 2005 for the Middle Santa Ana River Watershed through Resolution R8-2005-0001. They were then approved by the Office of Administrative Law (OAL) on September 1, 2006 followed by the US Environmental Protection Agency on (US EPA) May 16, 2007. More information can be found in Chapter 6 of the Santa Ana Water Board Basin Plan. Contact: Barbara Barry

Lake Elsinore Canyon Lake nutrient TMDLs
The Lake Elsinore/San Jacinto River watershed is located in Riverside County and includes the following major waterbodies: Lake Hemet, San Jacinto River, Salt Creek, Canyon Lake and Lake Elsinore. The total drainage area of the San Jacinto River watershed is approximately 782 square miles. Over 90 percent of the watershed (735 square miles) drains into Canyon Lake. Lake Elsinore is the terminus of the San Jacinto River watershed. TMDLs for nutrients were adopted on December 20, 2004 for Lake Elsinore and Canyon Lake through Resolution R8-2004-0037. They were then approved by the US Environmental Protection Agency on (US EPA) September 30, 2005. More information can be found in Chapter 6 of the Santa Ana Water Board Basin Plan.

The TMDLs are currently being reconsidered – proposed revisions to the Lake Elsinore Canyon Lake nutrient TMDLs
Contact: Barbara Barry

The Newport Bay watershed is located in Central Orange County in the southwest corner of the Santa Ana River Basin, about 35 miles southeast of Los Angeles and 70 miles north of San Diego (Appendix 1). The watershed encompasses 154 square miles and includes portions of the Cities of Newport Beach, Irvine, Laguna Hills, Lake Forest, Tustin, Orange, Santa Ana, and Costa Mesa. Mountains on three sides encircle the watershed; runoff from these mountains drains across the Tustin Plain and enters Upper Newport Bay via San Diego Creek. Newport Bay is a combination of two distinct water bodies - Lower and Upper Newport Bay, divided by the Pacific Coast Highway (PCH) Bridge. The Lower Bay, where the majority of commerce and recreational boating exists, is highly developed. The Upper Bay contains both a diverse mix of development in its lower reach and an undeveloped ecological reserve to the north, the 752-acre Upper Newport Bay Ecological Reserve and Nature Preserve, which is also a State Marine Protected Area. The watershed includes three freshwater subwatersheds (San Diego Creek, Santa Ana - Delhi Channel, and Big Canyon Wash), and two smaller freshwater tributaries, (Costa Mesa and Santa Isabel channels), all of which discharger directly into Upper Newport Bay. Contact: Terri Reeder

(Note: Basin Plan amendments for the Newport Bay watershed TMDLs for Selenium, Organochlorines Compounds, Nutrients, and Sediment can be found in Chapter 6 of the Water Quality Control Plan for the Santa Ana River Basin.)

Fecal Coliform TMDLs for Newport Bay

A Basin Plan amendment was developed and adopted by the Santa Ana Water Board at the June 3, 2022 public hearing and was approved at the State Water Board’s November 15, 2022 public hearing, to extend the deadline for attainment of the water quality objectives (WQOs) for the shellfish beneficial use (SHEL) in Newport Bay, from December 31, 2022, to December 31, 2030. The purpose of the extension is to allow additional time to complete studies that are currently in progress to determine whether there is a correlation between fecal indicator bacteria in water and fecal indicator bacteria and pathogens in shellfish tissue. A dry season study of bacteria in the water column and bacteria in shellfish was completed by the Southern California Coastal Water Research Project (Technical Report 1193). The study found no correlation between the SHEL WQOs in water and bacteria and pathogen levels in Pacific oysters in Newport Bay. A similar study for the wet season is currently underway.

Time Schedule Order Number R8-2019-0050 for the County of Orange, the Orange County Flood Control District, and the Cities of Tustin, Irvine, Laguna Hills, Laguna Woods, Costa Mesa, Santa Ana, Orange, Lake Forest and Newport Beach to comply with the Requirements Prescribed in Order Number R8-2009-0030 as amended by Order Number R8-2010-0062 (NPDES Permit Number CAS618030)

Copper TMDLs

TMDLs for Copper in Newport Bay were approved by the Santa Ana Water Board at the December 2, 2022 public hearing. Water Board staff are working on additional public outreach as required by AB 2108 in preparation for consideration of adoption of the Cu TMDLs by the State Water Board in 2023. For updates, Subscribe to the E-mail Notification List (Select "TMDL Newport Bay Copper - Metals").

RESOLUTION NO. R8-2022-0012 – Adopted December 2, 2022

Basin Plan Amendments for Copper (Cu) TMDLs for Regional Board Hearing - December 2, 2022