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ATC Associates Inc. v v 1117 Lone Palm Avenue, Suite B Modesto,California 95351 209-579-2221 11 a s s n ci Ae s N c_ Fax:209-579-2225 On April 8, 2004, Gregg In Situ, Inc. advanced a CPT sound boring (CPT-1) immediate down- gradient of the former USTs (UST#1 and UST#2 noted on Figure 2) and in the vicinity of MW- 3 to obtain a continuous description of the subsurface lithology. This location was chosen because groundwater samples collected from MW-3 historically contained the high concentrations of BTEX constituents with respect to samples collected from the other wells. A cone mounted with sensors in the tip was advanced into the ground using direct push rods by Gregg's CPT rig, which has a down pressure capacity of approximately 20 tons. The sensors measure the response of the soil to the force of the penetrating cone at five centimeter intervals allowing the subsurface stratigraphy to be characterized. The CPT boring was advanced to refusal at approximately 58 feet bgs. Following characterization of the subsurface material, a Hydropunch® type groundwater sampling system was advanced into the subsurface approximately 2 feet north of the initial CPT boring location to collect depth discrete soil and groundwater samples. Based on the stratigraphic profile indicated in the initial CPT sound boring, the Hydropunch® sampler was advanced to 19 feet bgs and the push rods were retracted exposing a stainless steel filter screen to the formation allowing for groundwater infiltration. A groundwater sample was collected by lowering a stainless steel bailer inside the hollow push rods. The groundwater collected inside the bailer was transferred to laboratory-supplied containers that were placed in a cooler chilled with ice for subsequent delivery to a State-certified analytical laboratory. After the collection of the first water sample, the soil sampler was attached to the Hydropunch® rods and advanced to 25 feet bgs to collect a soil sample from a relatively thick interval of clayey silt separating the upper and lower water bearing zones. After the collection of the soil sample, the Hydropunch® sampler was then advanced to 52 feet bgs where the next sand intervals were encountered to collect a water sample from the second water-bearing zone. The discrete groundwater and soil samples collected from 19 feet bgs (CPT1-W19), 25 feet bgs (CPT1-S25) and 52 feet bgs (CPTI-W52)were placed in a cooler chilled with ice for transport to the analytical laboratory. Selected soil samples from the GP and CPT borings were submitted to Argon Laboratories Inc. (ELAP #2359) of Ceres, California for analysis that included TPHg and BTEX utilizing EPA 8015B and 8021B methodologies, respectively, and for oxygenate fuel additives utilizing EPA 8260B methodology. Soil samples collected from borings GP2, GP3, and CPT1 did not contain detectable concentrations of TPHg, BTEX, or oxygenate fuel additives. The soil sample collected from boring GPI at approximately 10.5 feet bgs contained concentrations of TPHg, ethylbenzene, and total xylenes at 7.0 milligrams per kilogram (mg/kg), 0.052 mg/kg, and 0.14 mg/kg, respectively. No other analytes were detected in these samples. TPHg, BTEX, or fuel oxygenates were not detected in the sample collected from boring GPI at 15.5 feet bgs. Page 4 ("- %TC w:\17861\WP for Additional Subsurface Investigation Soil Vapor Study,and Modeling ...° ."T`. ..`