Bacterial Source Identification at Poche Beach – An Integrated Approach to Improving Beach Water Quality and Meeting TMDL Compliance Targets
Poche Beach is located in the City of San Clemente in Orange County, California. Historically, the ocean receiving waters at Poche Beach have been among the worst in the region for exceedances of water quality standards for indicator bacteria (enterococcus, total coliforms, and fecal coliforms) and it has been included in the adopted San Diego Beaches and Creeks Bacteria total maximum daily load (TMDL). The beach is located at the base of a relatively small drainage (4,400 acres) that is dominated by land uses that are common to the southern California coastal region (golf course, single family residential, and light commercial). In an effort to understand the sources of indicator bacteria in this coastal watershed and produce best management practices (BMPs) to improve water quality at Poche Beach, the City of San Clemente hired Weston Solutions, Inc. to conduct a bacterial source identification study. The final design of the study encompassed a multi-tiered adaptive approach with investigations of both anthropogenic and natural sources of bacteria. We used a suite of source tracking tools, including cutting edge molecular techniques, to assess a wide variety of potential bacterial sources and transport mechanisms including: assessments of groundwater recharge, over-irrigation, bacterial regrowth within the storm drain infrastructure and scour pond at the base of the watershed, and the contributions from the resident bird population at the beach. Based on recommendations from the study’s finding, the City implemented a trial BMP focused initially on the gulls at the beach. The results have yielded dramatic improvements in water quality of the ocean receiving waters at Poche Beach. During the entire period that the BMP was implemented, Poche met the water quality objectives for bacteria. This is in sharp contrast to the historically high bacterial concentrations that have plagued Poche Beach for decades. The results demonstrate the importance of thorough site-specific watershed assessments in identifying sources of indicator bacteria with a focus on implementing the most practical BMPs to improve water quality. This comprehensive, integrated approach, which relies on source controls and effective management, can serve as a model for reducing bacterial loads in coastal urban watersheds and improving water quality at recreational beaches.