Corrective Action Plan for the Risk-Based Remediation of the MOGAS Site, Myrtle Beach Air Force Base, South Carolina. Volume 1

Abstract

A comprehensive site investigation addressing soil, groundwater, surface water, and sediment contaminated with fuel hydrocarbons at the Motor Gasoline (MOGAS) Storage Area, Myrtle Beach Air Force Base (AFB), South Carolina, was conducted by Parsons Engineering Science, Inc. (Parsons ES). Field work was conducted to complete the corrective action plan (CAP) presented in this report in support of a riskbased remediation decision for the MOGAS site. Characterization field efforts for this investigation were conducted from January through September 1995. Selected source reduction technologies were field-tested at the MOGAS site from November 1995 to January 1996 to determine the effectiveness of these remedial techniques in treating site-related contamination.The risk-based remediation demonstration at the MOGAS site is sponsored by the United States (US) Air Force Center for Environmental Excellence (AFCEE) at Brooks AFB, Texas under contract F41624-93-C-8044, and is a component of a multi-site AFCEE initiative. The purpose of this initiative is to demonstrate how quantitative fate and transport calculations and risk evaluation, based on site-specific data, can be integrated. Consequently, this integration allows for rapid determination of the type and magnitude of corrective action required at a site to minimize contaminant migration, receptor exposure, and subsequent risks to the potential receptors. Riskbased remediation is designed to combine natural physical, chemical, and biological processes with low-cost source reduction technologies such as in situ bioventing, as necessary, to economically reduce potential risks to human health and the environment posed by subsurface petroleum fuel spills.The MOGAS site is located in the northwestern quadrant of the Base. Three 5,000-gallon underground storage tanks (USTs) were used to store gasoline at the site, and one 5,000-gallon UST was used for diesel fuel storage. The USTs were removed in 1993. Historical releases from at least two of these tanks have contaminated soil and groundwater with fuel hydrocarbons. Contaminated groundwater discharges to a manmade drainage ditch along the southern edge of the MOGAS site, resulting in surface water and sediment contamination. Free product was observed on the groundwater surface in the 1980s; however measurable free product has not been observed in site monitoring wells during the 1990s.The CAP for the MOGAS site follows South Carolina Department of Health and Environmental Control (SCDHEC, 1995) guidance for implementing risk-based corrective actions in the state. The guidance outlines a tiered approach for establishing corrective action requirements at specific sites. The tiered approach is based on an evaluation of potentially completed receptor exposure pathways from contaminated site media under both current and future land use scenarios.One objective of the CAP is to document any potential current risks to human health and the environment (i.e., ecological receptors) due to exposure to chemical 022/725522/7.WW6ES-1 cont...