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Report-Groundwater Inves..gation <br /> First Student Bus Facility(Former A.W. Hayes Facility) <br /> 2005 Navy Drive—Stockton, CA <br /> VOCs detected above the MCL during the December 2003 investigation conducted by <br /> Ramcon include cis-1,2,-Dichloroethene in MW-1 at a concentration of 220 ug/L; and <br /> trans-1,2,-Dichloroethene, which was detected in MW-1 at a concentration of 31 ug/L; <br /> cis-1,2-Dichlorethene, which was detected in MW-2 at a concentration of 730 ug/L• <br /> trans 1,2,-Dichloroethene, which was detected in MW-2 at a concentration of 36 ug/L; <br /> and cis-1,2,-Dichloroethene, which was detected in MW-4 at a concentration of 20 ug/L. <br /> VOCs detected above the MCLs for all three sampling events are summarized below in <br /> Table 5. <br /> Table 5— Cumulative Laboratory Test Results Summary <br /> Date Cis-1,2 Trans-1,2, <br /> Dichloroethene Dichloroethene <br /> MCL 6 ug/L) MCL 10 ug/L) <br /> 12/03 <br /> MW-1 220 ug/L 31 ug/L <br /> MW-2 730 ug/L 36 ug/L <br /> MW-3 ND ND <br /> MW-4 20 ug/L 3 ug/L <br /> 11/08 <br /> MW-1 1100 ug/L 94 ug/L <br /> MW-2 NA NA <br /> MW-3 ND ND <br /> MW-4 5.6u 1.2u <br /> 5110 <br /> MW-1 900 ug/L 110 ug/L <br /> MW-2 NA NA <br /> MW-3 ND ND <br /> MW-4 11 ug/L 3.0 u <br /> ug/L—microgram/Liter(parts per billion) <br /> ND—Not detected at concentrations greater than the method detection limit(MDL) <br /> NA-Not Available—MW-2 not sampled <br /> Field measurements presented in this report demonstrate that groundwater flow direction <br /> is approximately south 48° west and the gradient is 0.014 ft/ft. <br /> Because of the limited amount of data available during this reporting event (only 3 <br /> sampling events), it is difficult to determine whether the source of the VOC contaminants <br /> are from an on-site source (the former USTs or a failure in the existing wash rack and <br /> oil/water separator system), or from an off-site source (the surrounding properties are <br /> predominately industrial). As such, KR Environmental recommends to have MW-2 <br /> surveyed to Geotracker specifications, and to conduct a Quarterly Ground Water <br /> Monitoring of all four (4) wells in September (Third Quarter) 2010 to determine how the <br /> concentrations of VOCs may change in groundwater beneath the Site, and to determine if <br /> groundwater flow direction and gradient remain relatively constant. <br /> 6 <br />