Toxicity analysis underway for study revisiting copper TMDL in Marina del Rey Harbor

Researchers have begun analyzing toxicity data for a SCCWRP-led study examining whether existing regulatory targets for dissolved copper in Marina del Rey Harbor should be modified to more accurately reflect the ecological threat posed by copper.

At a meeting in December, the project’s technical advisory committee reviewed initial results that SCCWRP obtained via a toxicity analysis method known as the Water Effects Ratio (WER), which quantifies how chemical characteristics of a water body influence the bioavailability of metal contaminants.

Under the Los Angeles County harbor’s existing TMDL (total maximum daily load) regulatory target, Marina del Rey Harbor is required to reduce copper loading by 85%, which would require boat owners to make significant changes to the types of anti-fouling paint they typically use on the underside of boats.

The State Water Board is working to update guidance on how to use the WER method to set site-specific criteria for metal contamination in water bodies statewide; results from the Marina del Rey study are expected to inform this update.