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 (SMCWPPP), and Santa Clara Valley Urban Runoff Pollution Prevention Program (SCVURPPP) provided the match funds.
The primary objectives of the project were to:
This report presents an evaluation of a monitoring protocol (on-land visual assessment (OVTA)) to assess the levels of trash on land (streets and sidewalks) that could reach storm drain inlets as a surrogate for trash discharged from stormwater conveyances. Although several studies have predicted or quantified trash discharges from stormwater conveyance systems, none appear to have attempted to empirically measure reductions over time from this specific trash transport pathway. In the Los Angeles region, trash reductions are currently based on the geographical extent of trash control measure implementation and predetermined trash reduction values for each type of control measure implemented. In the San Francisco Bay Area, trash reductions in stormwater are calculated using three methods. The first two are equivalent to the two methods used in the Los Angeles region (i.e., areas treated by full capture systems and the results of agreed upon control measure specific studies). The third, on-land visual assessment, is currently Bay Area specific. The OVTA is a qualitative protocol that results in observations of trash levels on streets and sidewalks in specific assessment areas. The protocol assumes that the level of trash that is observed on streets and sidewalks is consistent with the level of trash discharged by stormwater conveyance systems. Quantitative monitoring and OVTA assessments were conducted at seven study areas located in the cities of Fremont, Oakland, and San Jose, California. Quantitative monitoring activities included the removal of trash from streets, sidewalks, and storm drain inlets. The trash collected was characterized in terms of weight, volume, and item counts. Quantification events were supplemented with qualitative OVTAs conducted before, after and between street sweeping, and before and after rainfall events. In addition to OVTAs conducted as part of the project, the results of approximately 3,100 OVTAs conducted at roughly 1,200 assessment sites by SCVURPPP and SMCWPPP were utilized to address the project monitoring questions.