Characterization and Environmental Management of Stormwater Runoff from Road-salt Storage Facilities

About the report:

The objectives of this study were to assess the quantity and quality of salt-contaminated water generated from stormwater runoff at VDOT's salt storage facilities and to evaluate management/treatment alternatives to reduce costs and better protect the environment. Data regarding detention pond surface area and volume, runoff area, and several key water quality constituents were collected from five randomly selected storage facilities in each of VDOT's nine districts, for a total of 45 sampling sites. Chloride concentrations were significantly greater than state and federal regulatory guidelines for drinking water and surface water quality criteria, with values routinely exceeding 2000 mg/L. Concentrations of total suspended solids and oil and grease were less than expected, with averages of 20 and 2 mg/L, respectively. The quantity of stormwater collected was higher than anticipated, with approximately 60 MG of contaminated runoff water being generated in an average rainfall year. Even if only the runoff generated during the 5-month winter maintenance season is considered, the volume of salt-contaminated water is in excess of 30 MG. Two alternatives to VDOT's disposal practices were examined: (1) management strategies to reduce the volume of salt-contaminated stormwater runoff generated at each facility, and (2) treatment of the runoff to remove the salt and subsequent release of the runoff back to the environment. Currently, VDOT disposes of the salt water by one of three methods: (1) connecting directly to a publicly owned treatment works system, (2) pumping and transporting the salt water to such a system by tank truck, or (3) applying the salt water to gravel roads to suppress dust temporarily. The average per gallon cost of VDOT's current method of pumping and transporting to a publicly owned treatment works system is approximately $0.13. If VDOT used a mobile ultrafiltration/reverse osmosis system, this cost would be cut by more than half. The $0.047 per gallon cost is also 58 percent of the $0.08 per gallon cost VDOT pays to use the wastewater for dust control. For a statewide annual treatment volume of 58.6 MG, this would result in an annual cost savings of $1.9 million to $4.9 million. It appears that the reverse osmosis treatment technology is worthy of additional exploration to ensure that operation problems and costs do not preclude its use by VDOT.

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