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IR , <br /> CLEARWATER <br /> C R O U P I N C <br /> E--V n—tnf Sul...s <br /> 1.0 INTRODUCTION <br /> This report presents the results of quarterly groundwater monitoring performed by <br /> Clearwater Group, Inc (Clearwater) on March 21, 1997 at 1002 North Yosemite Street <br /> in Stockton, California (Figure 1) The tasks included groundwater gauging, well <br /> purging, measuring dissolved oxygen, and groundwater sample collection <br /> 2.0 BACKGROUND <br /> No aboveground structures are present at the subject location, it is a vacant lot <br /> enclosed by a chain-link fence Records indicate that the subject site was used as a <br /> gasoline service station from 1961 to 1978, and that the underground fuel storage <br /> tanks were removed in 1980 <br /> The following subsurface investigations have been conducted at the site <br /> • A limited soil gas survey in 1990 by Evax Technologies, Inc , the soil gas survey <br /> indicated the possible presence of petroleum hydrocarbons in the soil <br /> • GeoAudit drilled and sampled six soil borings (up to 36 5 feet deep), laboratory <br /> analysis of soil samples collected by GeoAudit indicated the presence of relatively <br /> low levels of ethylbenzene in the soil around the western edge of the property <br /> • In October 1993, GeoAudit installed and sampled three groundwater monitoring <br /> wells (MW-1 through MW-3) at the request of the San Joaquin County Public <br /> Health Services Environmental Health Division (PHS/EHD), the results of the <br /> initial site assessment are presented in GeoAudit's November 1993 "Monitoring <br /> Well Installation and Quarterly Report" <br /> • At the request of the PHS/EHD, Clearwater installed monitoring wells MW-4 <br /> and MW-5 in August 1994 and installed MW-6 in September 1995 in order to <br /> assess the downgradient limits of the hydrocarbon plume <br /> • In September 1995, Clearwater also supervised the drilling of two vapor <br /> extraction wells (VW-1 and VW-2), two air sparging wells (SW-1 and SW-2) and <br /> one 81-foot deep investigative soil boring (CPT-7), a pilot test was conducted, and <br /> the results were presented in Clearwater's Report on Site Assessment Activities, <br /> Pilot Test, and Quarterly Groundwater Monitoring, dated December 15, 1995 <br /> In letters dated August 21, 1996 and March 25, 1997, the PHS/EHD stated that both <br /> the soil and groundwater contamination plumes have been laterally delineated. <br /> D-101 1Q97 1 Apnl 15, 1997 <br />