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F <br /> rl <br /> r.k <br /> and hydrocarbon sensor are set at a level such that the floating hydro- <br /> �4 <br /> carbons are removed with a minimum of ground water being pumped. In the <br /> recovery well at the ARCO site, EMM' Associates recommended the hydra <br /> purge pump be placed at 38 feet below ground surface and the petropurge <br /> pump be placed at 31 feet. These depths are periodically adjusted by <br /> -. Gettler-Ryan personnel to obtain optimal product recovery. <br /> The floating hydrocarbons and ground water recovered by the petropurge <br /> system ars pumped into a subsurface holding tank where the hydrocarbons <br /> y are separated and removed from the water. The ground water extracted by <br /> the hydropurge pump is pimped into a separate holding tank. This tank <br /> also serves as a separating tank for floating hydrocarbons in the event <br /> r that the water table is inadvertently drawn down to the hydropurge pump <br /> intake. The water held in this second tank is subsequently discharged <br /> " into the sanitary sewer from a discharge-Valve located at the bottom of <br /> the tank (Appendix 0 contains the discharge permit application). Both <br /> r tans are equipped with hydrocarbon and water sensors that will shut off <br /> the system to prevent the tanks from over topping. - <br /> At the time of system start-up in early August 1984, the ground water in <br /> the recnvery well was sampled. The sample was analyzed for the presence <br /> A of benzene, toluene and xylenes by gas chromatography followed by flame- <br /> ionization andphoto-ionization detection (see Appendi-- B, Chemistry <br /> Data). the results show high levels of all three compounds, with hen- <br /> zene at 14,000 ppb, toluene at 25,000 ppb and xylenes at 16,000 ppb. <br /> These high levels of dissolved gasoline constituents in the ground water <br /> would be expected since free-floating product was present in the well. <br /> Gettler-Ryan, Inc. has reported recovery of approximately 600 gallons of <br /> product. Product recovery was obtained by a combination of bailing the <br /> wells, capturi_ by the recovery system, and initial product recovery in <br /> monitoring wells with a vacuum truck. Since installation of the extrac- <br /> tion system, Gettler-Ryan has been monitoring the site for depth to <br /> liquid and thickness of floating product in all wells twice a week. <br /> PJO 438-22.04 7 <br /> .r <br /> Mork Associates- <br />