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1 ' Site Background Information - Ripon Farm Service • Page 6 of 9 • BTEX compounds have not been detected in wells MW-1 through MW-10 for at least three consecutive quarters. • DIPE has been detected in ground water samples from wells MW-2 through MW-4,MW-8, and VW-2A at concentrations as high as 17µg/l(MW-8).TBA has been detected in samples ' from wells MW-1 through MW-4, MW-8, and soil vapor wells VW-1 and VW-2 at concentrations as high as 360µg/l(VW-2B).MTBE has been detected in samples from wells MW-1 through MW-4, MW-6, and MW-8 at concentrations as high as 500 4g/1 (MW-8). TAME has been detected in well MW-8 at a maximum concentration of 38 µg/l. 1,2-DCA has been detected in wells MW-1,MW-2, MW-4, MW-9,and MW-10 at concentrations as ' high as 300 µg/1 (MW-4). i ' SOIL AND GROUND WATER REMEDIATION On 25,26,and 27 April 2000,four air-sparge pilot borings and eleven soil vapor extraction soil pilot ' borings were advanced at the site; with borings IAS 1 through IAS4 completed as 2-inch diameter air sparging wells, drilled to a total depth of 25 feet bsg with a 5-foot screen interval. Two vertical zones of remediation wells were installed as follows: borings VW3A, VW8, and VW9A were ' completed as vapor extraction wells,drilled to a total depth of approximately 13 feet bsg with 5-foot screen intervals, and borings VW3B,VW4, VWS, VW6, VW7, VW9B, VW10, and VW11 were completed as vapor extraction wells, drilled to a total depth of approximately 18 feet bsg and ' completed with 5-foot screen intervals. Soil samples were collected from air-sparge pilot borings IAS 1 to IAS4 ahead of the drill bit using ' a core barrel. TPH-g was detected in each of the samples at concentrations as high as 990 mg/kg. TPH-d was also detected in each sample analyzed at concentrations as high as 1,000 mg/kg. BTEX compounds were detected in each sample analyzed.Benzene was detected at concentrations as high 1 as 0.63 mg/kg at a depth of 18 feet bsg. The only fuel additive detected was 1,2 DCA at a concentration up to 20 micrograms per kilogram (gg/kg). A Solleco catalytic-oxidation soil vapor extraction (SVE) unit began operation at the site in December 2000. The system was monitored monthly during operation and after re-start events. During each monitoring event, the SVE flow rate, vacuum (potential), and concentrations of ' hydrocarbons in the extracted soil-vapor were measured, and a set of soil-vapor samples were collected by AGE personnel. The unit operated at an average extraction flow rate of 85 and ' 90 standard cubic feet per minute (cfm). A compressor-based EnviroSparge IAS system was installed at the site in August 2001.The IAS system delivered 6 cfm at a pressure of 10 pounds per square inch (psi), adequate to displace the static water within each sparge well. In addition, the dissolved oxygen in the ground water wells was measured to monitor the efficiency of the IAS system. ' Advanced GeoEnvironntental,Inc.