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V1117 Lone Palm Avenue <br /> f — Suite B <br /> +� Modesto, CA 953551 <br /> E +. 209.579.2221 <br /> ' Fax 209.579.2225 <br /> A S S O C I A T E S I N C - <br /> September 20, 1999 <br /> 54.13099.0001 ENVIRONMENTAL HEALTH DIVISION <br /> 304 E. Weber Ave.Third Floor <br /> P O. Box 386, Stockton CA 95201-0388 <br /> Approved ] <br /> Denied r� <br /> Mr. Harlin Knoll Conditions <br /> San Joaquin County Public Health ServicesIV <br /> Environmental Health Division pate 912-2- by- k _....__. <br /> 304 E. Weber Avenue, 3rd Floor <br /> Stockton, CA 95202 <br /> Subject: Workplan for Pumping Test and Remedial Investigation Feasibility Study at 304 <br /> North Acacia Avenue, Ripon, California <br /> Mr. Knoll: <br /> ATC Associates Inc., on behalf of the Ripon Unified School District, has prepared this workplan <br /> for performing a pumping test and remedial investigation feasibility study at the subject site <br /> (Figure 1). The purpose of the remedial investigation feasibility study is to evaluate groundwater <br /> extraction and treatment as a remedial option. ATC will perform a 24-hour pumping test and the <br /> results of the pumping test will be used to prepare the remedial investigation feasibility study for <br /> the site. The following paragraphs contain a detailed description of the scope of work to be <br /> performed. <br /> BACKGROUND <br /> In February 1991, one 500-gallon UST of unknown fuel type was removed; in August 1991, one <br /> 550-gallon unleaded gasoline UST was removed; in October 1991, 47 feet of single wall piping <br /> was removed; and, in December 1991, one 7,500-gallon unleaded gasoline UST was removed. <br /> Laboratory analysis of soil samples collected from beneath the former USTs and piping locations <br /> indicated the presence of detectable concentrations of total petroleum hydrocarbons. <br /> Discoloration of soil and a petroleum hydrocarbon odor were noted in the field. After the tanks <br /> were removed,the areas of the former tanks were backfilled. <br /> On April 23, 1998, an ATC geologist supervised the advancement of six soil borings to 21 feet <br /> below ground surface (bgs). Soil borings S131, S132, and S134 were placed in the vicinity of the <br /> former USTs, soil boring S133 was placed in the vicinity of the former dispenser, and soil borings <br /> S135 and S136 were placed at the southern edge of the former excavation area. A site plan with <br /> soil boring locations is shown on Figure 2. Soil samples and grab groundwater samples were <br /> collected from each boring. Analytical results indicated that the soil samples and the <br /> groundwater sample from boring S136 contained detectable concentrations of petroleum <br /> w:1130991reportslpumpwkp.doc 1 <br />