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b'\ <br /> Final Remedial Plan - Geweke <br />' 2 January 1992 <br /> Page 2 of 15 <br /> The fresh water bearing formation, consisting of alluvial sediments <br /> occurs in a shallower depth. These two aquifers are hydraulically <br />' separated from each other. The ground water is considered as <br /> beneficial use and is used for irrigation, municipal and industrial <br /> purposes with moderate utilization for domestic use (California ' s <br /> Groundwater, Department of Water Resources Bulletin no. 1.18) . <br /> 1. 2 , SITE SPECIFIC SETTING <br />' The following site specific information is obtained from two <br /> existing reports (Problem Assessment Report) prepared by PES <br />' Environmental, Inc. (PES) dated July 1991 and BCC report July 1990 : <br /> o The prevailing soil profile consists of sandy silt from the <br /> surface to a depth of 10 feet, fine to medium sand with <br />' alternating thin layers of sandy silt from 10 to approximately <br /> 25 feet, sandy silt with varying sand content from 25 to 47 <br /> feet, and fine to coarse sand with clay lenses from 47 to 75 <br /> feet (bottom of profile) . Saturated conditions were <br /> encountered at approximately 60 feet during the installation <br /> of the latest monitoring wells in May 1991. <br />' o When surveyed in May 1991, the water table indicated an <br /> average hydraulic gradient of 0 . 09 . The prevailing ground <br />' water flow direction is to the southwest. <br /> o An extraction rate of approximately 2 gallons per minute (gpm) <br /> was achieved during recent aquifer testing. <br /> 1. 3 . BACKGROUND AND PREVIOUS INVESTIGATIONS <br /> The Problem Assessment Report of PES is the source of the <br /> following: <br />' o The fueling facility at the site consisted of two 10, 000 <br /> gallon, one 6, 000 gallon fuel storage tanks and their <br /> appurtenant piping/ dispensers. These tanks and an additional <br />' 1, 000 gallon waste oil tank, were removed in 1985. An <br /> unauthorized release of hydrocarbons was encountered following <br /> the removal. <br /> o The impact of this release on the vadose and saturated zones <br /> was initially investigated by J.H. Kleinfelder, Inc. <br /> (Kleinfelder) in the later portion of 1985. In conjunction <br /> with this investigation Kleinfelder drilled four soil borings <br />