Laserfiche WebLink
1 <br />' 27 October 2003 <br /> AGE-NC Project No 98-0450 <br /> Page 7 of 17 <br /> ' 3.0 CORRECTIVE ACTION <br /> In-situ remediation methods, including SVE were the best treatment effectiveness for the <br /> ' hydrocarbon impacted soil and ground water encountered described at the site Based on <br /> hydrocarbon concentrations in soil and proximity to ground water, natural attenuation was not <br /> considered to be an acceptable remediation alternative The depth of impacted soil(45 feet)and the <br /> saturated `smear' zone (45 feet to 50 feet)would preclude an effective ex-situ soil remediation, the <br /> effectiveness to remove soil impacts along the northeast boundary is dependent on excavation slope <br /> stability and controls AGE recommended in-situ soil vapor extraction in conjunction air-sparging <br /> 1 <br /> 3 1 SITE FEASIBILITY TESTING <br /> On 12 May 1999, an 8-hour soil vapor extraction (SVE) test was performed on the site This pilot <br /> ' test was performed to provide SVE data prior to initiation of a full scale remediation system An <br /> induced vacuum potential was applied to the casing of vapor well VW-2,vacuum was monitored at <br /> surrounding observation points(BMW-1,BMW-2,BMW-3,BMW-4,BMW-5 and MW-5 and vapor <br /> '• well VW-1) A total of four soil vapor samples were collected during the pilot test TPH-g was <br /> detected in the soil vapor samples (vapor samples) at concentrations ranging from 19,000 µg/l to <br /> 23,000�Lg/l BTEX were detected in the gas/vapor samples at concentrations as high as 740 pg/I <br /> ' (xylene, VS-1) Analytical results of the soil vapor samples are included in Table 5 Based upon an <br /> effective vacuum potential of 1 0 inches of water,the calculated effective radius of influence at the <br /> site will be approximately 25 feet <br /> 1 <br /> 3 2 CORRECTIVE ACTION PLAN IMPLEMENTATION <br /> ' On 15 through 19 May 2000, 19 soil borings were advanced at the site The soil borings were <br /> completed as vapor wells VW3 through VW 11 and air-sparging wells IAS 1 through IAS 10 Vapor <br /> ' well pilot boring VW3 through VW5 were drilled at a 25 degree angle from vertical and were <br /> completed to a depth of 50 feet bsg with a ten-foot screen interval Vapor well pilot borings VW6 <br /> through VW8 were drilled vertically to 50 feet bsg and were completed as dual-screened vapor <br /> ' extraction wells These wells were constructed with one lower 10-foot and an upper 15-foot screen <br /> interval, from 40 to 50 feet bsg and 30 to 15 feet bsg,respectively Vapor well borings VW9 through <br /> VW 10 were drilled to a total depth of approximately 50 feet bsg and was completed with a ten-foot <br /> ' screen interval from 40 to 50 feet bsg Vapor well boring VW11 was drilled to a total depth of <br /> approximately 40 feet bsg and was completed with a 20-foot screen interval from 20 to 40 feet bsg <br /> ' Borings IAS 1 through IAS 11 were completed with a 5-foot screen interval from 50 to 55 feet bsg <br /> as air sparging wells As-built well diagrams are depicted in Appendix A A stratigraphic cross <br /> • <br /> Advanced GeoEnvironmental,inc <br />