An Analysis of the Benefits of Using Underground Tanks for the Storage of Stormwater Runoff Generated at Virginia Department of Transportation Maintenance Facilities

About the report:

The Virginia Department of Transportation (VDOT) collects millions of gallons of runoff at its nearly 300 salt storage facilities each year, with some portion of this water being reused for the generation of salt brine. Storing this collected stormwater runoff in tanks rather than ponds affords some advantages in that less water is collected; the water that is collected remains cleaner; and the water is more likely to be properly managed and disposed of when necessary.

The purpose of this study was to quantify the monetary benefits of using underground storage tanks for the temporary storage of salt-laden runoff generated at VDOT’s salt storage facilities. This was done by way of a simple cost analysis comparing the use of underground storage tanks to the open-pond systems more commonly used now. Information on the costs related to the purchase, construction, maintenance, and operation of both storage types was used to develop a simple cost estimation tool, i.e., a benefit/cost spreadsheet. The tool was structured so that modifications could be made based on site-specific information on precipitation, water disposal costs, brine usage, etc.

The study concluded that although the purchase price of underground storage tanks is substantially higher than that of ponds, the 50-year all-inclusive cost of tanks is similar to the cost of ponds for stormwater storage. Although the costs are highly variable and dependent on site-specific conditions, when the medium default values used in the benefit/cost spreadsheet are used, tanks are slightly cheaper than pond relining or new pond construction. As disposal costs increase above current values, storage by way of tanks will become an increasingly better option.

Based on this information, the study recommends that VDOT’s Environmental Division collaborate with the Capital Outlay Section of VDOT’s Administrative Services Division, residency administrators, and area headquarters superintendents to evaluate the option of using underground storage tanks for the storage of stormwater runoff from salt loading pads at locations that are replacing (relining) existing ponds or at facilities where new pond construction is being considered.

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