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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 17 gg/1(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 360 gg/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 gg/1 (MW-8) TAME has been detected in well MW-8 at a maximum concentration of 38 gg/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 gg/l (MW-4) ' SOIL AND GROUND WATER REMEDIATION On 25,26,and 27 April 2000,four air-sparge pilot bonngs 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 spargmg 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, VW5, 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 I 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 ' 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 GeoEnviron mental,Inc 1