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WORK PLAN ADDENDUM - May 1999 <br /> i West Clay Properties <br /> 639 West Clay Street, Stockton, California _ <br /> 1.0. INTRODUCTION AND SCOPE OF WORK <br /> At the request of Mr Dan Silva of West Clay Properties,Advanced GeoEnvironmental, Inc (AGE) <br /> has prepared this Site Assessment Work Plan for 639 West Clay Street, Stockton, California The <br /> location of the site is illustrated on Figure 1- Location Map Structures, well and boring locations <br /> are illustrated on Figure 2 - Site Plan <br /> This work plan is prepared in response to a 29 April 1999 meeting with the San Joaquin County <br /> Public Health Services - Environmental Health Division (PHS-EHD) and in accordance with <br /> guidelines established by the PHS-EHD and Central Valley Regional Water Quality Control Board <br /> (CVRWQCB) for the investigation of underground storage tank (UST) sites <br /> The purpose of this assessment is to define the lateral and vertical extent of petroleum hydrocarbon <br /> impact to soil and ground water at the former location of UST No 3 and the initial investigation of , <br /> impacted soil and ground water at the former UST Nos 1, 2 and 4 This Work Plan provides a , <br /> description of the scope of work and field procedures for the soil and ground water assessment <br /> activities <br /> 2.0. BACKGROUND <br /> Between March 1994 and August 1998, thirteen soil borings were advanced at the site Petroleum <br /> hydrocarbons were detected in soil samples collected at depths as great as 46 5 feet below surface <br /> grade (bsg) in borings advanced near the former location of UST No 3 Petroleum hydrocarbons <br /> were not detected in shallow borings advanced west and northeast of the former UST No 3 location <br /> or in borings advanced approximately 120 feet north of the former UST No 3 location (Table 1) <br /> The vertical extent of hydrocarbon-impacted soil was not defined in the area of the former UST No <br /> 3 ' _ <br /> UST Nos 1, 2 and 4 (UST cluster) were removed from the site in December 1998 Petroleum <br /> hydrocarbons were detected in samples collected beneath the USTs and dispenser island (Table 2) <br /> Further investigation has not been performed around the former UST cluster <br /> Based on the results of laboratory analysis of soil samples collected during previous investigations <br /> at the site and historical fluctuation in ground water elevation, the PHS-EHD is requiring additional <br /> assessment to determine the lateral and vertical extent of hydrocarbon-impacted soil and ground <br /> water The approximate lateral extent of impacted soil is illustrated on Figure 2 <br /> Site background and previous assessment activities were summarized in the Quarterly Monitoring <br /> Report and Data Summary- December 1997 and the Quarterly Monitoring Report -August 1998, <br /> Advanced GeoEn\ironmental,Inc <br />