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1 <br /> • <br /> t <br />' Sutter Office Center Pioject 2267-E <br /> February 18, 2002 Page 3 <br />' abandoned and filled with sand Standaid Oil took over this site and operated a service <br /> station at this location from the late 1960's until closure of this service station in <br /> December 1980 During this time, the underground storage tanks were removed from the <br />' site, according to the County Building Inspector's report <br />' A former UNOCAL Service Station occupied the northwest cornei of East Mines- Avenue <br /> and Califoi nia Street, 100 feet north of the subject property, from 1922 until its closure in <br /> 1992 This service station was remodeled in 1967, and two leaking 1,000 gallon gasoline <br />' tanks and a 550 gallon waste oil tank were removed fiom the southwest corner of that <br /> parcel These tanks were replaced by two new 10,000 gallon tanks and a 280 gallon waste <br /> oil tank in the western poition of the site Monitoiing wells, installed in 1994, showed <br /> that the underground storage tanks at this site had leaked, resulting in petroleum <br /> hydrocarbons extending to a depth of 45 feet below the ground surface <br /> I <br /> FIELD INVESTIGATION AND SAMPLING <br /> Seven soil and groundwater samples (Probes A through G) were obtained by p direct- ush <br /> piobes at this site on May 22, 2000 , at the approximate locations shown on Plate 2, <br /> Location of Probes and Monitoring Wells Three additional probes (Probes H, I and J), <br /> two on-site and one offsite, were obtained on January 31, 2002, at the request of the San <br /> I Joaquin County Environmental Health Department, to evaluate the horizontal and vertical <br /> extent of residual hydrocarbons in the soil and groundwater <br /> I The direct-push probes were conducted by Vironex Environmental Field Services <br /> A Geoprobe "5400" subsurface sampling system was used for the small diameter probes <br /> that extend to a depths of 90 feet Soil samples were obtained at 10 foot intervals, and <br /> Igroundwater samples were collected at the completion of drilling by the use of four foot <br /> long, 1-inch diameter PVC, machine perforated well Screen New PVC piping and <br /> sampling tubing was used at each probe to prevent cross contamination The PVC pipe <br /> was removed from the probes after sampling, and the probe holes were filled with neat <br /> cement <br /> HYDRO-GEO CONSULTANTS INC <br />