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A <br /> Project Descriptions AddanBrown <br /> HYDROCARBON REMEDIATION, WYOMING <br /> AdrianBrown was retained to remediate source areas of hydrocarbon contamination at a Superfund site <br /> in Wyoming. The site had been used as a natural gas compressor station since 1965. Groundwater at the <br /> site was discovered in 1985 to contain trace amounts of dissolved hydrocarbons,including benzene, <br /> toluene,ethylbenzene,and xylenes (BTEX). The site was divided into two operable units,groundwater <br /> remediation and remediation of source areas. Groundwater pump-and-treat,soil vapor extraction, and <br /> free-product recovery systems were installed to address the groundwater operable unit. Air sparging was <br /> chosen to address the remaining source areas. <br /> A process area and a former flare pit were identified as BTEX source areas. Hydrocarbons from the <br /> process area migrated vertically into the soil. Relatively low-volatility hydrocarbon fluids remaining <br /> after burning migrated into the soil from the former flare pit. After reaching the water table,the BTEX <br /> compounds from both source areas were smeared vertically due to fluctuating groundwater levels and <br /> were spread horizontally. <br /> AdrianBrown designed and installed an air sparging system to address the source areas. We performed <br /> a Remedial Design investigation to collect soil and soil-gas samples needed to properly design the <br /> system. Groundwater samples were collected to determine the pre-sparging concentrations in the <br /> shallow aquifer. <br /> After the data from the Remedial Design investigation were analyzed,AdrianBrown designed and <br /> implemented a pilot-scale air sparging system to optimize operational parameters. Dissolved oxygen <br /> measurements in groundwater and oxygen,carbon dioxide,and methane concentrations in the soil vapor <br /> were used to evaluate the pilot system and determine full-scale air flow rates and pressures. <br /> The full-scale system was installed and was operated from October 1993 through March 1995. Air <br /> injection occurred through 5 clusters of sparging wells,with air extraction from the vadose zone through <br /> the existing soil vapor extraction system. Soil,soil gas, and groundwater samples collected after <br /> operation ceased showed that the air sparging,system effectively remediated the source areas. <br /> Following cessation of pumping from the groundwater remediation source area in 1996,AdrianBrown <br /> has coordinated quarterly groundwater sampling at the site. Results show that BTEX concentrations <br /> have consistently remained below cleanup standards. Final closure of the site after completion of all <br /> post-remediation sampling is expected in 1999. <br />