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' PHASE H GROUNDWATER INVESTIGATION <br /> SAN JOAQUIN COUNTY HUMAN <br /> SERVICES AGENCY BUILDING <br /> STOCKTON, CALIFORNIA <br /> ' 1.0 INTRODUCTION <br /> This report presents the methodology and results of the Phase II Groundwater Investigation of <br /> the area on and surrounding the site of the San Joaquin County Human Services Agency building <br /> located at the intersection of San Joaquin Avenue and Washington Street in downtown Stockton, <br /> ' California (Figure 1) The project was mandated by the San Joaquin County Department of <br /> Health Services Environmental Health Division (EHD) in order to determine the extent of <br /> hydrocarbon presence in groundwater resulting from the leakage of one or more former <br /> ' underground fuel storage tanks Roy F Weston Inc (WESTON) was requested and authorized <br /> to perform this investigation by the San Joaquin County Capital Projects Division Although the <br /> original project site consisted of a relatively small area on the corner of San Joaquin Avenue and <br /> Washington Street, the Phase II investigation "site" encompasses several city blocks bound by <br /> the five new monitoring well locations (Figure 2) <br /> ' 1.1 Previous Work <br /> In April 1988, WESTON managed the removal of nine underground fuel storage tanks from the <br /> site and collected soil samples from beneath the tanks These tanks had been used to store the <br /> various fuels sold at a gas station which had been previously located on the corner of <br /> ' Washington Street and Sutter Street The following is a summary of the types and capacities <br /> of the tanks removed <br /> ' • one 5,000 gallon super unleaded <br /> • one 10,000 gallon unleaded <br /> • one 10,000 gallon leaded <br /> ' • two 550 gallon leaded <br /> • one waster oil tank (capacity not specified) <br /> • three previously abandoned sand filled tanks (former contents unknown) <br /> ' An initial soil and groundwater investigation (Phase I) was performed on this site by WESTON <br /> in late 1988, the results of which are presented in a Problem Assessment Report (PAR) entitled <br /> ' "Underground Fuel Storage Tank Site Investigation " dated February 20, 1989 The Phase I <br /> investigation consisted of the following activities <br /> ' • Soil boring and sampling <br /> • Installation of three groundwater monitoring wells and groundwater sampling <br /> • Chemical analysis of soil and groundwater <br /> ' • Interpretation of Results <br /> lip <br /> ' R"smc WP 1 <br /> o6MIM <br />