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S ECOR - -- <br /> Ms. Devra Lewis <br /> April 8, 2005 <br /> Page 3 <br /> monitoring point is needed to the west of the furthest SVE well to determine lateral <br /> radius of influence. A soil vapor monitoring point also is needed south of the <br /> screened portion of "ASVE-6." Furthermore, all of the monitoring points are <br /> proposed to a total depth of five feet below ground surface. Based on the depth of <br /> the SVE wells, about nine feet below ground surface, the L&M OU needs at least one <br /> location with multiple depth monitoring points to evaluate the effectiveness of the <br /> system at capturing vapors at and below the depth of the SVE Well. <br /> Soil vapor monitoring point PSV-7 has been included to determine lateral radius of <br /> influence to the west of SVE-2 and soil vapor monitoring point PSV-9 has been included to <br /> determine lateral radius of influence to the south of ASVE-6. One dual nested PSV well is <br /> proposed at the location of PSV-5/PSV-6 with screened sample points located at 5 feet and <br /> 10 feet below ground surface (bgs), respectively. Additionally, existing monitoring wells <br /> MW-9, MW-10, and MW-21 and DPE wells DPE-6, DPE-11, and DPE-12, which are <br /> screened across the zone of extraction, will allow for additional radius of influence <br /> monitoring. <br /> • 8. Proposed SV-1 appears to be located to evaluate the influence from SVE-1, which <br /> is not consistent with the remaining four proposed soil vapor monitoring points, <br /> which are evaluation the "ASVE" wells. The L&M OU needs to include a discussion <br /> of each of the proposed soil vapor monitoring points with the rationale for their <br /> locations. <br /> The rationale for each PSV well is discussed below. Please note that the nomenclature for <br /> soil vapor monitoring points has been amended from SV to PSV in order to differentiate <br /> between soil vapor points conducted for the HHRH. <br /> PSV-1: This soil vapor monitoring point was proposed to evaluate the effectiveness of well <br /> SVE-1. The location was established out side of the excavation limit so that the liner <br /> placed at the bottom of the excavation would not be punctured. <br /> PSV-2: This soil vapor monitoring point was proposed to evaluate the effectiveness of well <br /> ASVE-1. <br /> PSV-3: This soil vapor monitoring point was proposed to evaluate the effectiveness of well <br /> ASVE-2. <br /> PSV-4: This soil vapor monitoring point was proposed to evaluate the effectiveness of <br /> wells ASVE-3 and ASVE-4. <br /> PSV-5/PSV-6: These dual nested soil vapor monitoring points are proposed to evaluate <br /> the effectiveness of wells ASVE-5 and ASVE-6 at depths of approximately 5 and 10 feet <br /> below ground surface (bgs), respectively. Further discussion of these wells is included in <br /> the response for comment 7. <br /> Stockton Parcel 2A:Agency Response Letter 6-10-04, SECOR Intemational Incorporated <br />