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1 <br /> 2005 4`h Quarter Groundwater Report <br /> Frontier Transportation, Inc. <br />' February 13, 2006 <br /> Page 3 <br /> In August 2005, BEA installed three shallow groundwater wells Monitoring wells MW- <br /> 19, MW-20 and MW-21 were advanced to 20' bgs and screened from 5' bgs to 20' bgs See <br /> Figure 2 for well locations <br /> 1 3.0) SITE GEOLOGY/HYDROGEOLOGY <br /> 1 The site is located on the boundary of the Sacramento Valley and the San Joaquin Valley <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 /> 1 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 /> 1 clay (Reference Site Charactenzation Report, Twining Laboratories, October 16, 1996) BEII <br /> encountered predominantly clays with traces of interbedded sands from 0' to 25' bgs during well <br /> advancement in January of 1998 <br /> 3 V" <br /> First subsurface water was encountered at depths from"to lAgs during tank removal <br /> and monitoring well installation at this site in 1995 and 1996 Since then, first subsurface water <br /> 1 •� has been encountered beneath the site between 6' and 10' bgs The groundwater flow is generally <br /> a western direction beneath the site(See Figure 3, Groundwater Gradient Map) Fhstonc first <br /> subsurface groundwater data identified a west or southwest flow beneath the site Groundwater <br /> 1 was also encountered at approxunately,35' bgs during installation of deep monitoring wells MW- <br /> 12 through MW-16 and MW-18 The potentiometnc groundwater levels in these deep wells, <br /> however, were similar to the first subsurface water levels <br /> 1 <br /> Hydrographs,are presented as Figures 4 and 5 for shallow groundwater monitoruwells <br /> 1 (up to 25-feet bgs) and deep groundwater monitoring wells (40-feet bgs) Groundwater levels <br /> beneath the site appear to be affected by seasonal recharge In general, the groundwater is at its <br /> yearly low in the winter and yearly high in the spring <br /> 1 4.0) QUARTERLY GROUNDWATER SAMPLE RESULTS <br /> 1 BEA contracted Del-Tech to collect groundwater samples from 13 of the monitoring wells <br /> at the site on December 15, 2005 for laboratory analysis Monitoring wells sampled were MW-1, <br /> MW-2, MW-3R, MW-9, and MW-13 through MW-21 Groundwater parameters (pH, <br /> 1 temperature, and conductivity)were measured before, during, and after well purging (See <br /> Appendix A for Momtonng Well Field Logs) <br /> 1 Groundwater samples were analyzed for TPH-g using EPA methods 8015 and for BTEX, <br /> 1 <br /> i <br /> 1 <br />