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• ARCADISGERAGHTY&MILLER <br /> In thein <br /> op Fon of ARCADIS Geraghty & Miller, previous work by <br />' UNOCAL's consultants has resulted in delineation of the lateral extent of groundwater <br /> impact in the shallow zone The scope of work proposed herein is designed to <br /> delineate the vertical extent of site groundwater impacts and to finalize the database <br /> upon which a subsequent remedial strategy will be developed and a corrective action <br />' plan work plan written <br /> OBJECTIVES <br />' The objectives of the limited subsurface investigation are to <br /> 1 Vertically delineate the dissolved-phase petroleum hydrocarbon plume <br />' downgradient of wells with elevated concentrations of dissolved-phase <br /> petroleum hydrocarbons, and <br /> 2 Evaluate the vertical groundwater gradient <br />' Completion of these objectives is expected to provide sufficient data to <br /> support completion of the delineation of the vertical and lateral extent of impact to <br /> groundwater and to form the basis for development of corrective action plan <br /> SITE BACKGROUND AND SETTING <br />' The site is a vacant lot situated on the northwest corner of East Miner Avenue <br /> and California Street(Figure 1)in the City of Stockton, California The site is situated <br /> in an area of retail stores and hotels Topography m the site vicinity is flat-lying, at an <br />' elevation of approximately 15 feet above mean sea level (MSL) McLeod Lake and <br /> the Stockton Deep Water Channel are situated approximately one-half mile to the west <br /> The site was an operating UNOCAL Service Station from 1922 until 1992 <br />' Two 1,000-gallon gasoline and one 550-gallon waste oil underground storage tanks <br /> (USTs) were removed from the southeast corner of the subject site in 1967 <br /> (collectively referred to hereafter as "the 1967 tanks') Data related to soil testing at <br />' the time of UST removal are not available These USTs were replaced with two <br /> 10,000-gallon gasoline and one 280-gallon waste oil USTs (collectively referred to <br /> hereafter as the "the 1992 tanks' situated in a common excavation in front of the <br /> station building <br /> The most recent service station consisted of a three-bay service station <br />' building, three product dispenser islands(D-1 through D-3), and two gasoline and one <br /> waste oil USTs in a common excavation The site is currently an unpaved vacant lot. <br /> Pertinent features of the former service station are shown on the Site Plan(Figure 1) <br /> 1 <br /> 1 <br />