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s-- Site Background Information Former Stefano's Gas Station Page 4 of 6 SOIL DESCRIPTIONS Sandy silt, clayey silt and silt with an orange brown to grey brown color was generally encountered from surface grade to total depth of each boring. Silty sand was encountered at 30 feet and 45 feet bsg,and medium-to fine-grained sand was identified below 54 feet bsg in boring OZ2.Grey brown sandy and silty clays were encountered between 30 and 35 feet bsg in boring SVE2 and between 40 and 55 feet bsg in borings OZ1 and OZ2. Grey hydrocarbon stained clay was encountered in boring OZIand OZ2 at 50 feet bsg. SOIL VAPOR EXTRACTION PILOT TESTING As per the WES Addendum for Workplan for Soil Vapor Extraction Testing dated 12 September 2003 two soil vapor extraction feasibility pilot tests were conducted on 27 and 28 January 2004. On 27 January 2004, the upper layer, screened from 12 to 27 feet bsg,was tested using vapor well SVE1 as the extraction well. On 28 January 2004, a second pilot test was conducted on the deeper impacted areas closest to ground water at the site using vapor well SVE2,screened from 30 feet bsg to 35 feet bsg, as the extraction well. The pilot tests were performed to evaluate SVE as a remedial alternative. The tests were conducted using a vapor extraction system (VES), VACLEEN 1000G, manufactured by Environmental Techniques. The VES unit consists of a positive displacement blower, driven by an internal combustion (IC) engine. Propane was used as a supplemental fuel source to start the engine and maintain performance. Hydrocarbon vapor was destroyed as part of the internal combustion process. Emissions from the engine were routed through two catalytic converters to maximize the destruction rate of the extracted hydrocarbon vapors. A total of three soil vapor samples were collected during each pilot test. Soil vapor samples were collected at two-hour intervals from the sample port of the extraction well to measure hydrocarbon concentrations in the extracted gas. The samples were collected in Tedlar bags using an air pump. During the pilot tests, the SVE unit was operated at 1,950 to 2,375 RPM, gas flow rate ranged between 40 and 60 cfm(standard cubic feet per minute),and OV readings ranged between 400 and 2,280 ppm. The induced vacuum measured at the extraction wells ranged from 14 to 33 inches of water. Sufficient vacuum was measured in the observation wells during the deeper SVE test to indicate that a vertical connection may exist across stratigraphic layers at the site. AGE determined the effective SVE radius of influence by plotting the maximum vacuum measured at the observation wells during pilot testing versus the distance from the extraction well on a logarithmic scale;the effective radius of influence was determined by drawing a best-fit line though these data points. At a vacuum pressure of 0.10 inches of water, the radius of influence is approximately 40 feet for both screened intervals; at a vacuum pressure of 1.0 inches of water, the Advanced GeoEnvironmental,Inc.