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1 <br /> These results imply that gasoline migration through the soil was primarily downward until <br /> the groundwater interface was reached, followed by lateral migration in the capillary fringe. <br /> The groundwater gradient at that time was east-northeast,probably in response to drawdown <br /> in Lodi Municipal Well #1, which was located approximately 350 feet east of the site; this <br />' may explain the high concentration of hydrocarbons in the water sample from MW-3. <br /> However, the regional hydraulic gradient is to the southwest, which probably accounts for <br /> the petroleum hydrocarbons detected in MW-2. <br />' 2.3 Initial Monitoring <br />' According to information provided to GeoAudit by the client, no further work was <br /> performed at the site until November 1991. In November of 1991, Earth Systems <br />' Environmental (ESE) attempted to measure the depth to groundwater and collect water <br /> samples in wells MW-1 through MW-3. ESE reported that water levels had dropped below <br /> the screened intervals in MW-2 and MW-3 and the wells were dry. However, both water and <br /> floating product were present in MW-1, but no sample was collected. The product thickness <br /> was not reported by ESE. The depth to water in MW-1 was 60.12 feet. No further <br /> monitoring occurred in 1991. - <br /> 1 2.4 Installation of Monitoring Wells MW-4 and MW-5 <br /> In January 1992, PHS/EHD required replacement of MW-2 and MW-3. Monitoring wells <br /> MW-4 and MW-5 were installed in June 1992. GeoAudit supervised the drilling and <br /> collected the samples. <br />' No petroleum hydrocarbons were detected in any of the soil samples from MW-4 or MW-5. <br /> Low to moderate concentrations of hydrocarbons were detected in water samples from both <br /> MW-4 and MW-5. Due to low water levels, none of the other wells could be sampled in <br /> June 1992. Measurement of the depth to groundwater in MW-1, MW-4, and MW-5 <br /> indicated that the groundwater gradient had rotated to the southwest, in accord with the <br />' regional gradient. (The City of Lodi Municipal Well #1 was abandoned prior to 1992.) <br /> Based on these results, GeoAudit recommended that two additional wells be installed to <br />' define the limits of petroleum hydrocarbon plume in groundwater, one to the northwest of <br /> the building and one southwest of MW-5. Subsequently,PHS/EHD required three additional <br />' wells, all located east or north of MW-1. <br /> 2.5 Installation of Monitoring Wells MW-6 through MW-8 <br />' Monitoring wells MW-6, MW-7, and MW-8 were drilled in April 1993. Two soil samples, <br /> one from the existing groundwater interface (55 feet) and one from the former groundwater <br />' interface (45 feet), were collected from each well and analyzed for total petroleum <br /> hydrocarbons (TPH as gasoline) and volatile aromatic hydrocarbons (BTE&X). A water <br /> sample was also collected from each well. No TPH or BTE&X were detected in the soil or <br /> C.Pjc.l A.&s.t„;em,I.. 4 <br /> AN A Artsb QA313-W 1.47 <br /> 1 <br />