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A 7 Monitoring Well Installation Report Speedy Mart,8200 N Highway 99 Page 2 of 8 level The nearest surface water body is an unlined canal located approximately 30 feet south of the site The Mokolumne Aqueduct is located approximately 2,000 feet west of the site and the Calaveras River is located approximately 7,000 feet to the south SITE BACKGROUND On January 28, 1998, three 8,000-gallon gasoline underground storage tanks (USTs), dispenser pumps, and associated piping were removed from the property Soil contamination was noted during UST removal operations and soil samples collected from beneath the removed USTs and pump Island revealed significant levels of petroleum hydrocarbon constituents As an interim abatement measure, the excavation was lined with 6 mil plastic and the soil was returned to the hole Analytical results of soil samples collected beneath the USTs and dispensers are presented in Table 1 Soil sample locations are shown on Figure 2 On September 23, 1998, Jim Thorpe Oil, Inc excavated approximately 166 cubic yards of impacted soil The soil was transported directly to Forward Inc landfill for disposal A strong petroleum odor and some visible discoloration were noted in the upper portion of the removed soil As soil removal continued, the bottom of the excavation began to clean up, and the west and south walls appeared to have only occasional areas of minor contamination However, the north and east walls still showed evidence of discoloration The removal of the contaminated soil was supervised by William J Hunter, RG, of Wm J Hunter & Associates Analytical results are �1 presented in Table 1 On September 23 & 24, 1998, approximately 369 cubic yards of clean fill dirt and 54 cubic yards of gravel base was brought in to fill the excavation The soil was compacted as required by San 1 Joaquin County Because of the high levels of contamination and the proximity to a water supply well on the property, the San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) required that the vertical limits of contamination be evaluated, and the domestic well be sampled and its integrity determined A subsurface assessment was performed by Ground Zero in November 1998 The investigation consisted of drilling two pilot borings (CPT1 and CPT2) using a cone penetrometer testing (CPT) rig to identify subsurface stratigraphy and advancing additional soil borings as necessary to collect soil and groundwater samples Interpretations of soil type were confirmed through traditional soil logging techniques using ASTM protocol Soil samples were collected from three borings (SBI, SB2, SB3) at significant changes in lithology, based upon the CPT data collected from the pilot borings The locations of CPT and soil borings are presented on Figure 3 Analytical i esults indicated that relatively low levels of petroleum hydrocarbons, including benzene and methyl tent butyl ether (MTBE), were detected in soil in the vicinity of the former USTs and dispenser island Analysis of the groundwater sample collected from in the vicinity of the former USTs contained elevated levels petroleum hydrocarbon constituents, including MTBE Soil and groundwater analytical groundzeltu1eburglwe1hpt doe