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GJeologicaCTechnics Inc. Page 4 <br /> Groundwater Monitoring Report <br /> Project No. 750.2 ' <br /> March 22,2001 <br /> 1.3 Laboratory Analyses <br /> The groundwater samples collected on February 22, 2001, were delivered to Sherwood Lab <br /> ` (Department of Health Services Certification No. 1400), of Hilmar, California for analysis, <br /> Y s <br /> The groundwater samples were analyzed for: <br /> Benzene, Toluene, Ethyl Benzene, and Xylene(BTEX). <br /> • TotaI Petroleum Hydrocarbons as Gasoline (TPH-G) by EPA method 5030/8015(M). <br /> Additional samples were sent to Entech Analytical Labs, Inc. from Sherwood Labs for the <br /> analysis of: <br /> • Fuel oxygenated compounds (MTBE, DIPE, ETBE, TAME & TBA) by EPA method <br /> 8260. <br /> The detection limits for the above analyses are listed in Table 2 of Appendix A and the lab <br /> data is presented in Appendix B. <br /> 2.0 FINDINGS AND DISCUSSION <br /> The results of the groundwater sample analyses show the following- <br /> Well <br /> p Y g <br /> • Well MW-1 is impacted with gasoline range petroleum hydrocarbons (TPH-G, BTEX, <br /> & MTBE) and this is consistent with past events, suggesting that contaminants from the <br /> soil are leaching into the groundwater at the source area at a steady rate. <br /> • The discretely screened deep well MW-101 contained BTEX, TPH-G and MTBE <br /> concentrations above the laboratory reporting limits. The concentrations have decreased <br /> since its first sampling on December 1, 2000. Additional monitoring is necessary to <br /> determine contaminant trends. <br /> �, • Cross gradient well MW-5 contained 209 ugll TPH-G, suggesting that preferred <br /> t <br /> migration pathways in the vadose zone might actually be channeling the contaminants to <br /> the north. <br /> Vertical groundwater gradient was calculated and determined to be downward and ' <br /> greater than the horizontal gradient of the water table, suggesting that the contaminants <br /> in the water table may be transported to deeper depths in the subsurface. i <br /> • Oxidation-Reduction Potential measurements (Table 4) are positive for all the wells, <br /> suggesting that the volume of contaminats leaching into groundwater is minimal and <br /> L that biodegradation of the contaminants is at a rate sufficient enough to keep the <br /> BTEXITPH-G plume in a small area around the source with out depleating the oxygen <br /> to a level to slow the reaction process. <br /> - f <br /> �I <br /> � i <br />