Coyote Creek-Metals TMDL


Coyote Creek drains a watershed of 165 square miles, 85.5 square miles of which lie in north Orange County, with the remainder in Los Angeles County. The upper watershed contains some open space, most of which is used for oil production. However, most of the watershed is highly urbanized with a mixture of residential, commercial, and industrial development. Coyote Creek flows along the border between Orange and Los Angeles counties and finally flows into the San Gabriel River just above its tidal prism.


The Los Angeles Regional Water Quality Control Board (LARWQCB) found that metals loads in the San Gabriel River watershed, including Coyote Creek, may be harmful to aquatic life and impair the water supply. The LARWQCB Staff Report did not indicate any dry weather impairments in Coyote Creek. However, analysis of storm samples collected by the Los Angeles County Department of Public Works indicated too many exceedances of the copper, lead, and zinc chronic criteria from the California Toxics Rule.

Consequently, the LARWQCB adopted the San Gabriel River and Impaired Tributaries Metals and Selenium TMDL on July 13, 2006. These include wet weather TMDLs for copper, lead, and zinc in Coyote Creek. No dry weather TMDLs were adopted for the creek.

However, the Orange County Stormwater National Pollutant Discharge Elimination System Permit is issued by the Santa Ana Regional Water Quality Control Board (SARWQCB). Although the SARWQCB has not adopted TMDLs for Coyote Creek, it deferred to the LARWQCB and incorporated requirements in the Stormwater Permit to reduce the load of copper, lead, and zinc in Coyote Creek.

At this time, the County of Orange and watershed cities are developing a work plan to reduce metals loads in Coyote Creek, as required by the Stormwater Permit, until a full implementation plan can be developed.