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n, AppAled GvO.Sj/sPemS 4191-E Power Inn Roacf, Sacramento,CA 951126 (916)452.2901 <br /> •FREMONT e COSTA MESA • SACRAMENTO e HOUSTON <br /> January 31, 1989 <br /> 0927SEPP <br /> AGS 86102-3 <br /> Mr. Steve Epperson <br /> Beacon oil Compa,f <br /> 525 West Third Street <br /> Hanford, California <br /> Subject: Letter report of quarterly ground-water monitoring at <br /> { Beacon Station No. 3-492, 470 North Main Street, <br /> Manteca, California. <br /> Mr. Epperson: <br /> A geologist from our office was present at Beacon Station No. <br /> 3-492 in Manteca, California on September 6, 1988, to purge and <br /> sample three ground-water monitoring wells. This work was <br /> � completed at the request of Beacon Oil Company as part of our <br /> ongoing environmental investigation at the site. <br /> The site is located on the southeast corner of the intersection <br /> of North Main Street and Alameda Street in Manteca. The location <br /> of the station is shown on the Site Vicinity Map (Plate P-1) . <br /> Applied GeoSystems previously installed three 4-inch-diameter <br /> ground-water monitoring wells (AGS Report No. 86102-1, dated <br /> December 16, 1986) . The locat_ons. of the wells relative to the <br /> site facilities are depicted on the Generalized Site Plan (Plate <br /> P-2) . Previous work summarized in our Work Plan (AGS Report No. <br /> 86102-2 dated May 26, 1987) suggests that soil in the area <br /> immediately adjacent to and below the tank cavity is contaminated <br /> ® with hydrocarbons. <br /> The depth to ground water was measured in each monitoring well <br /> prior to purging and sampling. When corrected for changes in <br /> topography, these data indicate that the change in elevation of <br /> the ground-water surface among the three wells is less than the <br /> instrument error (0.02-foot over the required distarice) ; <br /> therefore, the ground-water potentiometric surface is inferred to <br /> be essentially flat. similar results have been obtained during <br /> _ - - - previous--sampling <br /> --events--The-data-indicate--that- the--ground--- <br /> water surface has dropped an average of 3.68 feet since the last <br /> measurement. <br /> After the initial water levelswere measured, samples of ground <br /> !'�f watiar from near the air-fluid interface were collected for <br /> i <br />