Toxicity evaluation of highway stormwater runoff

This paper presents the results of two major studies evaluating the toxicity of stormwater runoff generated from the urban and non-urban highways in California. Two major toxicity studies were: (1) statewide highway runoff toxicity evaluation and (2) hydrographic (rst- ush) toxicity evaluation of runoff from highly urbanized highways. Extensive grab and composite runoff samples were collected from numerous highway sites throughout the state of California for multiple storm events and multiple years. Wide ranges of toxicity testing, including the three U.S.EPA standard species, marine species, green algae growth, and MicrotoxTM were performed on grab and composite samples. The results obtained revealed that the highway runoff was generally toxic, and the toxicity was mostly associated with heavy metals and organic compounds such as herbicides, pesticides, and surfactants. While outside the scope of this study, an independent performance evaluation of stormwater treatment showed that toxicity removal after Best Management Practice (BMP) was possible, even though some in fluent samples entering the BMP were toxic.