A Method For Monitoring and Analyzing Litter in Freeway Runoff as Part of the Caltrans Litter Management Pilot Study

Trash and debris in storm water is a threat to aquatic wildlife, is aesthetically unpleasant, smells, can reduce drainage conveyance capacities, and can attract vermin. Despite improved awareness and increased spending on litter control, data on the movement of litter and debris through urban areas are scarce. This paper describes a two-year monitoring project, conducted in the Los Angeles region, that assesses the performance of several Best Management Practices (BMPs) intended to reduce the quantity of litter in freeway runoff as part of a Caltrans Litter Management Pilot Study (LMPS). Measurements of rainfall, runoff, and the amount of litter and debris [defined as material larger than five millimeters (1/4 inch)] are taken at both control sites and sites where BMPs are employed (treatment sites). The unique litter sampling equipment, the BMPs adopted, and the methodology are described, and some preliminary monitoring results are presented.