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r.. B. Concentration contours of contaminants found and those remaining in soil and groundwater, including lateral and vertical extent of groundwater and soil • contamination. t..r - �., Total Petroleum Hydrocarbons (TPH)-as-gasoline and methyl tertiary butyl ether (MTBE) are key constituents of concern at this site. An isoconcentration map showing the post-remediation lateral extent of MTBE in site groundwater is shown on Figure 8. The pre-remediation lateral extent of TPH-as-gasoline in site soil and the locations of cross-section A-A` and B-B' are illustrated on Figures 9. Vertical isoconcentration maps depicting pre-remediation TPH-as-gasoline isoconcentration contours for cross-sections A-A' and B-B' are included as Figures 10 and 11. 9. Zone of influence calculated and assumptions used for subsurface remediation system and the zone of capture attained for the soil and groundwater remediation system. The SVE system capture zones relative to the lateral extent of impacted soil are shown on Figure 5. The capture zone dimensions are based on a 20-foot radius of influence with an average extraction rate of 10 cubic feet per minute (cfm) per well. From June 1999 through June 2000, ENSR Consultants (ENSR) operated a soil vapor extraction (SVE) system at the site. Initially, ENSR extracted from VW-1 D, VW-1S, VW-2S, VW-3, and VW-4. After several months of operation, air sparging was initiated in MW-1. According to ENSR, the remediation system removed over 7,000 pounds of gasoline hydrocarbons from the subsurface. On August 24, 2000, Ramage Environmental supervised the drilling of a soil boring (CPT-1A) to a depth of 100 feet through the former UST location (Figure 2). To �,. confirm the effectiveness of remediation efforts, soil samples were collected every 10 feet. As summarized in Table 5, the soil sample results indicated that except for 560 milligrams per kilogram (mg/kg) of TPH-as-gasoline in soil at a depth of approximately 10 feet below ground surface (bgs), the vadose zone soil was effectively remediated by the SVE system.