MADABHUSHI, Sriram, madabhs@columb26.dhec.state.sc.us, SHRADER, A. Arthur, shradeaa@columb26.dhec.state.sc.us and MINER, Read S., minerrs@columb26.dhec.state.sc.us,
Bureau of Underground Storage Tank Management, SCDHEC, 2600 Bull Street, Columbia, SC 29201

Remediation by Natural Attenuation (RNA) is a remedy where naturally occurring physical, chemical and biological processes reduce petroleum concentrations to acceptable levels. The Underground Storage Tank program of the South Carolina Department of Health and Environmental Control has developed a method to determine if RNA as a sole cleanup approach is appropriate in achieving cleanup goals. Using site-specific conditions and applying a simple mass-balance equation, the assimilative capacity of the aquifer for RNA can be determined. A computer program has been developed to predict if cleanup goals can be met. The model prediction is then validated over time by onsite measurements. Of over 100 sites where RNA is identified as a sole cleanup approach, nearly half have met the cleanup goals or are projected to meet goals in a reasonably short period of time. Ongoing monitoring confirms that when properly applied to a site, RNA can be accurately predicted and the approach is an effective method for achieving remedial goals and risk management.