Specialists in Environmental Remediation, Ecology and Information Management
Work at this site was performed under an AOC between the client and USEPA Region III. Benzene was detected at elevated concentrations in groundwater in fractured bedrock at this facility. Light non-aqueous phase liquid (LNAPL) was also present in several measuring points. Through several characterization events, it was determined the source of the Benzene and LNAPL were historic releases from on-site Used Oil UST. To ensure no further releases would occur, the tank was removed. All affected soils surrounding the tanks were also removed and transported to an approved landfill.
To address this site, AGES designed a Multi-Phase Extraction (MPE) system, through which both groundwater and soil vapor are extracted simultaneously. The groundwater table is lowered to dewater the saturated zone so that the Soil Vapor Extraction (SVE) process can by applied to the newly exposed soil. This allows the Volatile Organic Compounds (VOCs) sorbed on the previously saturated soil to be stripped by the induced vapor flow and extracted. Soluble VOCs present in the extracted groundwater are also removed.
To refine the MPE system requirements, AGES conducted a pilot test at the site for a total of 60 days. Approximately 28,000 gallons of groundwater were extracted from the subsurface through three (3) four-inch diameter bedrock wells. A recovery rate of approximately 4 gallons per minute (gpm) reflects the average rate during system operation. Air and water samples were collected periodically throughout the test and analyzed for Benzene, Toluene, Ethylbenzene and Xylenes (BTEX) and Total Volatile Organic Compounds (VOCs). Based on lab analytical data, over 10 pounds of VOCs were removed during the pilot test. The MPE pilot test was also successful at removing at significant volume of LNAPL from the subsurface.
Based on the success of the pilot test, additional active remediation was not required. Monitoring of natural attenuation for remaining dissolved phase Benzene has therefore been performed. Benzene levels in groundwater have been significantly reduced over time. LNAPL has not been detected in measurable quantities in any wells or piezometers at the site since the conclusion of the pilot test. In addition to removing LNAPL, application of the MPE technology has expedited the clean-up process at this site and will allow the client to sell the property without deed restriction.
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