Characteristics of Storm-Water Runoff from Highway Construction Sites in California

Abstract

Fifteen highway construction sites were monitored by the California Department of Transportation (Caltrans) to assess the water quality of storm-water runoff from the sites. Caltrans conducted a study to generate sufficient water quality data to further develop management strategies and evaluate existing best management practices. A wide range of construction sites was selected for monitoring throughout the state. Both flow-paced composite and single-grab samples were collected and analyzed at these sites for a total of 72 station–storm events during the 1998–1999 and 1999–2000 wet seasons. Results obtained during the 2-year characterization study indicate the following: ( a) Caltrans construction-site runoff constituent concentrations detected during this study are less than typical Caltrans and non-Caltrans highway runoff constituent concentrations, with the exception of total chromium, total nickel, total phosphorus, total suspended solids (TSS), and turbidity. ( b) The concentrations of TSS and turbidity likely are due to the disturbed soils present at most construction sites. ( c) The origin of the high concentrations of total chromium, total nickel, and total phosphorus concentrations is unknown. Concentrations of these constituents varied between sites, so it is possible that site-specific soils and vegetative conditions contributed to the concentrations of these constituents. ( d) A correlation ( R2 values greater than 0.5) was observed between TSS runoff concentrations and particulate runoff concentrations of chromium, copper, and zinc, indicating that minimizing particulate matter may reduce total metals concentrations.