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2��a 'i�` 4,�s, �. ;` '% a`' 'Axi`•a`� T.xfr'�+ "g -� j <br /> Y�'. r'F`u r� pyo •�..�iN'..� 1 Wa, <br />:-a <br /> k- <br /> INTRODUCTION <br /> The following report presents the results of an investigation to evalu- <br /> ate the affectiveness of a gasoline recovery system located at the ARCO <br /> service station located a*908 Benjamin Holt Drive in Stockton, Cali- <br /> fornia (see Figure l). The report includes (1) a description of the <br /> regional and local hydrogeologic setting, (2) a review of EMCON's <br /> previous site investigation, (3) a discussion of the installation of the <br /> remedial-action system, (4) evaluation of the systems performance, and <br /> T (5) conclusions and recommendations. A brief site history follows. <br /> On May 24, 1984 a broken leak detector was discovered it a submersible <br /> pump near the tank complex. The leak reportedly resulted in an <br /> estimated loss of 2,000 gallons of gasoline. As a rE',s;It of the loss, a <br /> site investigation was immediately initiated by EMCON and Gettler-Ryan <br /> in Iate May 1984. All piping was tested, and the underground tanks and <br /> surrounding soil fill were excavated. New tanks were installed in the <br /> ( same area on June 1, 1984. <br /> EMCON's site investigation consisted of drilling 12 exploratory wells to <br /> determine the local hydrogeologic conditions (i.e., geology, ground- <br /> water flow direction, and extent of hydrocarbon contamination). <br /> Floating product was detected in seven wells varying in thickness from <br /> .16 to over 3 feet. Based on the results of the investigation a hydro- <br /> carbon recovery well was installed in late July 1984 to remove the <br /> floating product on top of the ground-water table. <br /> The results of EMCON's investigation show that the recovery well is <br /> properly functioning and capturing floating product beneath the ARCO <br /> service station. Docus.ented product recovery has been approximately <br /> 600 gallons since the loss was discovered. An unknown amount of product <br /> may have been recovered during tank replacement activities. Currently <br /> small amounts (1/4 inch or less) of floating product have been detected <br /> in five monitoring wells. Total dissolved gasoline constituents in <br /> - wells without floating product range from 430 to 80,000 parts per <br /> billion (ppb) 1n_—the other--vel+.v-. <br /> ... AJD 4•"38-22.04 1 <br /> Emcon Associates <br />