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UM <br /> Ms. Lori Duncan Page 5 <br /> San Joaquin County Environmental Health Department <br /> January 28, 2005 <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> On December 1 and 2, 2004, two additional groundwater monitoring wells were drilled and installed to <br /> assess the lateral and vertical extent of petroleum-impacted groundwater at the site. Monitoring well <br /> MW-7 was installed off-site across Brentwood Drive to assess shallow groundwater conditions down <br /> gradient of the station. Monitoring well MW-8 was drilled on-site adjacent to the current UST locations <br /> to assess the vertical extent of impacted groundwater. Groundwater samples collected from well off-site, <br /> MW-7 reported Iow concentrations of GRO, MtBE and 1,2-DCA. Soil samples collected during the <br /> drilling of on-site well MW-8 contained only very low concentrations of GRO and BTEX, which would <br /> be consistent with current groundwater concentrations found in this area. Samples collected from well <br /> MW-8 reported concentrations of GRO and BTEX in the groundwater at 95 feet bgs. <br /> I <br /> URS recommends that the groundwater data from at least two additional rounds of sampling be <br /> evaluated prior to conducting any additional assessment activities. URS will continue to conduct <br /> 1 quarterly groundwater monitoring of the wells at the site. <br /> If you have any questions or comments regarding this letter, please call Mr. Vernon Elarth at(916)679- <br /> 2299. <br /> Sincerely, <br /> + URS Corporation Americas <br /> \S��RI-D GE0�0 <br /> ?AU(ell. <br /> No. 7 20 <br /> i Michael Hall Vernon Elarth R.G * Exp , <br /> 1 Staff Geologist Project Manager -9 ��\P <br /> �OF CALwO <br /> Attachments: <br /> Table 1 Soil Analytical Data <br /> Table 2 Soil Fuel Oxygenate Analytical Data <br /> Table 3 Groundwater Analytical Data <br /> Table 4 Groundwater Fuel Oxygenate Analytical Data <br /> Figure 1 Site Location Map <br /> Figure 2 Site Map Showing New Well Locations with Groundwater Analytical <br /> Data <br /> K:IWprocessV5 RP ARCO\00548\2004 well install\Add site Assess Rpt 04.doc <br />