Characterization and environmental management of storm water runoff from road salt storage facilities

The Virginia Department of Transportation (DOT) is responsible for maintaining more than 57,000 mi of roadway; a major part of that responsibility is implementation of Virginia DOT's anti-icing program. In FY 2003, the agency purchased more than 570,000 tons of sodium chloride; this salt is stored at nearly 300 locations statewide. This study's objectives were to assess the quantity and quality of salt-contaminated water generated from storm water runoff at Virginia DOT's road salt storage facilities and to evaluate management and treatment alternatives to reduce costs and better protect the environment. For the first objective, data concerning detention pond surface area and volume, runoff area, and several key water quality constituents were collected from 45 randomly selected sampling sites. Chloride concentrations were significantly greater than those specified in state and federal regulatory guidelines, with values routinely exceeding 2,000 mg/L. The quantity of storm water collected was higher than anticipated, with approximately 60 megagallons (MG) of contaminated runoff water generated in an average rainfall year. For the second objective, two alternatives to Virginia DOT's disposal practices were examined: management strategies to reduce the volume of salt-contaminated storm water runoff generated at each facility, and treatment of runoff to remove salt and subsequent release of runoff back to the environment. Currently, the agency disposes of salt water by one of three methods at an average cost of $0.13 per gal. If Virginia DOT used a mobile ultrafiltration and reverse osmosis system, the cost would be cut by more than half. For a statewide annual treatment volume of 58.6 MG, an annual cost savings of $1.9 to $4.3 million would result.