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IV oa a 07 June 2012 AGE-NC Project No. 95-0184 ay. Page 3 of 14 �,. � n IN-SITU AIR SPARGING PILOT TEST / SJR From 11 November through 16 November 2009, an IAS pilot test was performed at the site; a soil vapor extraction pilot test was performed simultaneously. This pilot test was performed to provide data to evaluate the feasibility of air sparging as a remediation method at the site. An air injection rate of approximately 1 cubic feet per minute (cfm)was maintained for the start of the test period. The flow rate was then increased to approximately 1.5 cfm through the duration of the pilot test. Field measurements, collected from the observation wells throughout the duration of the IAS pilot test included, SVE vacuum pressure (VW-5A), ground water depth and dissolved oxygen. The vacuum was measured in inches of water at the SVE well manifold using a Magnehelic differential pressure gauge; ground water depth was measured using a Solinst water level meter; and dissolved oxygen (DO) was measured using a dissolved oxygen meter. During the IAS pilot test, only minor fluctuations in ground water elevation were measured. Significant increases in ground water elevation during the IAS pilot test would be indicative of ground water mounding which may cause the dissolved hydrocarbon plume to migrate. No trends of increasing ground water elevation were observed at the site. The depth to ground water did fluctuate at well VW-513, with a steady increase of two feet over the first two days of the pilot test and then stabilizing thereafter. The initial DO measurements indicated no significant background dissolved concentrations at the site. A plot of DO values versus time during the IAS pilot test indicated very sharp increases in DO readings at surrounding wells during initial 24 hours of air-sparging. High DO was measured in well VW-4 following active air-sparging and less pronounced DO concentrations were measured in wells VW-2A and EW-1. However, concentrations decreased to near non- detect levels after approximately 24 hours in several wells monitored on the site. RECOMMENDATIONS FOR REMEDIATION OF HYDROCARBON- IMPACTED GROUND WATER AND SOIL SOUTHERN UST AREA AGE believes that an in-situ method would be more effective in both cost and performance over a "pump and treat' ex-situ method. The performance of field scale pilot studies for ground water extraction have been completed. Remediation of impacted ground water should be conducted concurrently with soil remediation to prevent re-contamination of remediated soil. In-situ air sparging combined with soil vapor extraction, across the southern UST area dissolved plume appears to be a viable alternative for remediation of both soil and ground water in the vicinity of the former UST locations. Advanced GeoEnvironmental,Inc.