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dclayton LFOUI CES 1.0 INTRODUCTION Clayton Group Services, Inc. (Clayton)prepared this workplan to install additional monitor wells associated with the former Union Oil Company of California (Unocal) and Morton Paint (Morton) operations near Weber and Lincoln Avenue in Stockton, California(Figures I and 2). The workplan is submitted on behalf of Unocal and Alco, which have agreed to investigate areas east of the centerline of former Harrison Street between Mormon Slough to the south and the Stockton Deep Water Channel to the north. Other parties are performing investigations west of the centerline of former Harrison Street. Previous environmental investigations have been conducted on and around this area between 1989 and 2001. These investigations have included numerous soil borings, groundwater monitor wells, a geophysical survey, and test pits. Laboratory analyses of soil and groundwater samples have reported the presence of petroleum hydrocarbons, metal compounds, volatile organic compounds (VOCs), and semi-volatile organic compounds (SVOCs) at the Site. The objective of this investigation is to install additional monitoring wells to complete the delineation of petroleum hydrocarbons and related compounds east of former Harrison Street. 2.0 BACKGROUND The information presented in this section was obtained from a variety of the previously issued reports for the Site, as described in Section 3.0 below. 2.1 SITE DESCRIPTION The property associated with the former Unocal and Morton operations is currently owned by the City of Stockton(City), and is on portion land that the City refers to as "Parcel 2A". Parcel 2A currently consists of undeveloped relatively flat, fallow land located on the southwest comer of the intersection of West Weber Avenue and North Lincoln Street in Stockton, San Joaquin County, California (Figure 3). It is south of the Stockton Deep Water Channel, Weber Avenue, and an office building complex. To the west, south, and east, respectively, are apartments (Delta Gateway Apartments), the Mormon Slough, and a museum. Currently, Parcel 2A is generally unused, except for a small area of the northern portion that is used for parking of automobiles. Surface runoff from Parcel 2A currently flows into storm drain inlets on within the parking area and on Lincoln Street and Weber Avenue. _2.2 SITE GEOLOGY Sediments at and in vicinity of the Parcel 2A consist predominately of silt and clayey silt, which is interbedded with generally thin (up to 5 feet thick), laterally discontinuous beds of clay, sandy silt, silty sand, and sand. The depth to groundwater has been measured 1 PUSAMPROJECTSC001\036.9 Unocal Unccin and Weber\ 0100.02)\wOln(dm=1 c