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� 3 Mr. Jeffrey Wong Page 2 found in the samples collected beneath Tank #3 or Tank #4. No detectable concentrations of EDB were found in any sample. Total lead concentrations appear to be within the range of naturally occurring, background concentrations. Analytical data are summarized in Table 1. UST and soil sample locations are depicted on Figure 3. The condition of Tank #2 (described by the County inspector as "good") and the lack of significant odor and discoloration noted by the inspector above a depth of 11 feet suggests that the primary source of contamination at the site may have been the adjacent Tank #1 which was noted to have holes. Fill and native soil within the Tank#1 excavation were described as having "severe" odor and discoloration from the surface to the sampling depth of 10 feet. Hydrogeologic Setting The site is located in east central Stockton approximately one mile west of Highway 99. The nearest naturally occurring body of surface water is the Calaveras River, located approximately one mile to the north. Approximately 1/2 mile north of the property, between the property and the Calaveras River is the Stockton Diverting Canal, a tributary to the River. Surface elevation at the site is approximately twenty one feet above sea level. Based upon published data from the San Joaquin County Flood Control and Water Conservation District (Spring 1997 Groundwater Report), groundwater is expected to be encountered at a depth of approximately 55 feet below grade in the site vicinity. Historical low groundwater is estimated to have been approximately 80 feet below grade (Fall 1994 Groundwater Report) and historical high groundwater (Spring, 1986) was approximately 45 feet below grade. Historically, groundwater flow has been predominantly toward the northeast although the property is located within an area subject to repeated variations in flow direction and gradient. Soils in the site vicinity are expected to be primarily fine grained with coarse grained interbeds. Workplan In order to investigate the lateral and vertical extent of soil contamination resulting from the former USTs and to determine if groundwater has been impacted, Ground Zero proposes drilling and sampling four soil borings at the approximate locations shown on Figure 4. The central boring will be taken to the depth of historic-low groundwater, approximately .SU-feet, unless compelling field evidence indicates that soil contamination terminates well above the historical high groundwater depth (45-fW). The total depths of the peripheral borings, which are intended to laterally define soil contamination, will be determined in the field based upon evidence of contamination. h&Ms\wodcp1w