SITE INFORMATION AND CORRESPONDENCE

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San Joaquin '%..,zy Air Pollution Control District Page 2 UST removal operations and soil samples collected from beneath the removed USTs and dispensers revealed significant levels of petroleum hydrocarbon constituents. As an interim abatement measure, the tank excavation was lined with 6-mil plastic sheeting and the soil was returned to the hole. 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. 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. 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 Joaquin County. Subsurface Investigation Subsurface assessments were performed by Ground Zero between November 1998 and July 2004 to evaluation the extend of contamination in soil and groundwater beneath the site. The investigations consisted of drilling two pilot borings using a CPT rig to identify subsurface stratigraphy, advancing additional soil borings as necessary to collect soil and groundwater samples, installing and sampling fifteen groundwater monitoring and/or extraction wells including three deeper zone wells, and initiating free product recovery and groundwater extraction. Groundwater was initially encountered at a depth of approximately 56-58 feet below ground surface (bgs) and is currently measured at a depth of approximately 68-74 feet bgs in site wells. Borings and well locations are shown on Figure 2. Extent of Hydrocarbons in Soil and Groundwater Laboratory analysis of soil samples collected from borings within and peripheral to the former tank/excavation pit have defined the lateral extent of soil contamination. Vadose soil contamination of significance was identified only in vadose zone and capillary fringe zone samples from borings SBI, S132, SB3, MWI, and VW1, each of which was drilled in the vicinity of the former USTs and dispensers. Soil samples from peripheral borings did not contain contaminants in the vadose zone, although wells MW2, MW6, and MW 12 contained low levels of hydrocarbons in soil samples collected from the capillary fringe zone. Relatively minor levels of soil contamination are present between the bottom of the tank pit excavation (approximately 15-17 feet bgs) and the water table (currently approximately 70 feet bgs). Below this depth saturated soil appears to be minimally impacted. Ground Zero has estimated that approximately 500-525 pounds of TPHg and approximately 40-70 pounds of MTBE are present in the vadose zone soils beneath the site. Soil analytical results are presented in Tables 1 and 2. Groundwater in wells MWI, MW2, MW3, MW4, MW5, MW6, MW12, EW2, and VWI in the shallow aquifer beneath the site have been impacted with MTBE, but only wells MW 1, MW2, and VW1 are impacted with TPI-Ig and BTEX constituents. The wells with greatest impact are wells MWI, MW3, MW4, and VW1, with lower Ievels of contaminants in wells MW2, MWS, MW6 GAGROUNDZE\TULESURGNapor Extraction perrnits\VEScvrltr.DOC