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CLEARWATER <br /> t G R O U P <br /> • Enuirnnmenla!Servers <br />' gradient Refer to Figure 4 for dissolved phase hydrocarbon distribution at the site from groundwater samples <br />' collected on February 14, 2002 <br /> Purpose of Additional Activities <br />' Based on the significant sorbed-phase and dissolved-phase contaminant concentrations and distribution beneath the <br /> site, Clearwater proposed the testing of engineered in-sttu remedial technologies that would reduce the sorbed-phase <br />' and dissolved-phase contaminant mass over time, and mitigate the potential for this contamination to act as an <br /> ongoing source of dissolved-phase contamination The proposed tests consisted of <br />' a Step-interval tests groundwater extraction(GWE)tests, <br /> • Combined GWE/SVE tests, and <br />' • Combined GWE/SVE with air sparge(AS)tests <br /> 1 In order to effectively test these technologies,Clearwater proposed to install two additional wells at the site <br /> I <br /> • One dual-phase remedial well (DPW-1) to test combined GWE/SVE, and <br /> lie • One air sparge well(AS-1)to test sparging <br /> Drilling and Well Installation (DPW-1 and AS-1) <br /> Prior to drilling, permits were obtained from the San Joaquin County Department of Health Services and the site was <br />' marked by Underground Service Alert(USA)to identify utilities leading to the site <br /> On February 22, 2002, Clearwater supervised Mitchell Drilling Environmental (MDE), a C-57 licensed contractor <br />' based in Rancho Cordova, California, in drilling and installation of DPW-1 and AS-1 (Figure 2) MDE used a CME <br /> 75 truck-mounted drill-rig equipped with hollow-stem augers to drill the bormgs for the wells MDE used 10-inch <br />' diameter augers for the DPW-1 boring, and 8-inch diameter augers for the AS-1 boring The boring for DPW-1 was <br /> advanced to a total depth of 30 feet bgs, and the boring for AS-1 was advanced to a total depth of 25 feet bgs <br />' During drilling, soil samples were collected at five-foot intervals for sedimentologic verification purposes only Soil <br /> samples were screened for the presence of petroleum hydrocarbon vapors with a Photovac 2020 photo-ionizing <br />' OVM detector Boring logs and well construction diagrams are attached <br />' A well was constructed in each boring DPW-] was built with 4-inch diameter PVC well materials Well screen <br /> . (0 02-inch slot) was extended from 30 feet bgs (the bottom of the boring) to 10 feet bgs, and coupled to solid riser <br /> pipe extending to the surface The annular space was filled with Lonestar#3 sand from the bottom of the boring to <br /> 1 <br />' ZB178C Feas Test Report 3 May 9, 2002 <br />