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• Quarterly Groundwater Monitoring Report <br />' Frontier Transportation <br /> 0199-068 <br /> February 11, 1999 <br /> Site Layout Map). Soil samples were collected every five feet. Laboratory analysis of soil <br /> samples identified no detectable concentrations of TPH-g, BTEX, or MTBE. Groundwater <br /> samples were subsequently collected. Results are tabulated in Table 1. <br /> 3.0) SITE GEOLOGY/HYDROGEOLOGY <br /> The site is located on the bound of the Sacramento Valle and the San Joaquin Valle <br /> �'Y Y q Y <br /> within the west-central portion of the Great Valley Geomorphic province of California. The <br /> Great Valley has been filled with a sequence of older to younger alluvium of Pliocene to Holocene <br /> age which overlay sedimentary rocks of Cretaceous to Tertiary age. These sedimentary units, in <br /> turn, overlay a crystalline basement of Paleozoic and Mesozoic metamorphic and igneous rocks. <br /> The shallow subsurface geology in the site vicinity is a heterogeneous mix of gravel, sand, silt, and <br /> clay(Reference, Site Characterization Report, Twining Laboratories, October 16, 1996). BEII <br />' encountered clay and a heterogeneous mix of clay from 0' to 25' bg in January of 1998. Two <br /> cross sectional depictions of the site are provided as Figure 3 and Figure 4_ <br /> First subsurface water was encountered at depths from l I'to 12' bg during tank removal <br /> and monitoring well installation at this site in 1995 and 1996. BEII encountered shallow <br /> subsurface water between 6' and 10'bg. Data collected in December of 1998 identified the flow <br />' of groundwater in a generally western direction beneath the site (See Figure 5, Groundwater <br /> Gradient Map). <br /> 4.0) QUARTERLY GROUNDWATER SAMPLE RESULTS <br /> On December 10-11, 1998,BEII collected groundwater samples from MW-1 through <br /> 1 MW-7 for laboratory analysis. Groundwater parameters (pH, temperature, and conductivity) <br /> were measured before, during, and after well purging (See Appendix A for Groundwater <br /> Parameters). Groundwater samples were analyzed for TPH-d, TPH-g, and BTEX with MTBE <br /> using EPA methods 8015 modified for diesel, 8015 modified for gasoline, and 8260, respectively. <br /> Laboratory analysis results for all monitoring episodes are presented in Table 1 and Table 2_ <br /> Recent analytical reports are included as Appendix B. <br /> 2 <br />