This report is one of three technical reports of Tracking California's Trash – a Proposition 84 Storm Water Grant Program project funded in large part by the State Water Board. BASMAA and its project partners – 5 Gyres, City of Fremont, City of Oakland, City of San Jose, San Mateo Countywide Water Pollution Prevention Program, and Santa Clara Valley Urban Runoff Pollution Prevention Program provided the match funds.
The primary objectives of the project were to:
This report presents information on developing, testing, and evaluating monitoring methods designed to accurately calculate trash loading rates in stormwater conveyance systems and receiving waters that vary in type, size, flow, and location. Standardized and reproducible monitoring methods to empirically measure trash loading (i.e., flux) in either stormwater discharges or receiving waters have not been available. A literature review was carried out to analyze existing methods and projects that monitored trash within water bodies. The review found that few municipalities and entities in the U.S. have attempted to evaluate concentrations and loads of trash discharged in receiving waters. The biggest source of references was from studies designed to monitor plastic pollution in marine environments, mostly at sea. Methods used during the project were based primarily on NOAA’s Marine Debris Monitor and Assessment Document, Algalita’s River Los Angeles Study, and 5 Gyres’ global estimate that compiled data from multiple partners to determine a global estimate for plastic pollution. These studies suggested that using multiple trawls to capture samples of plastic pollution floating on the surface of a water body, with some focus on what is in the water column, would be the most successful approach. Therefore, methods described in these studies were modified to capture trash samples in receiving waters to accommodate the higher flows observed in rivers, creeks, and channels during wet weather events. Monitoring methods were evaluated in four creeks (three in the Bay Area: Colma Creek, Coyote Creek, and San Mateo Creek and one in Los Angeles: Arroyo Seco, a channelized river in Pasadena).