SITE INFORMATION AND CORRESPONDENCE

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Former Continental Grain 1805 Harbor Street, Stockton, CA Page 2 The proposed area of excavation is 15 feet wide (north-south) by 48 feet long {east-west), and extends to 12 feet bsg in the vicinity of the tank pit which may not be adequate. The proposed limit of the excavation in an east-west direction was based on analytical results of soil samples collected along the east-west axis of the former tank pit area: SB-1, SB-2, SB- 12, NIW-2, and MW-4,but there is little analytical data to delineate the northern limit. The closest soil samples north of the tank pit were collected from MW-1,which is located about 72 feet away from MW-2 and the tank pit. Additional information on the northern extent of the soil contamination closer to the tank pit is required to determine the optimal area of excavation necessary to bring the site toward closure. EHD requested by the letter dated October 5, 2001 that a calculation of the hydrocarbon mass impacting soil and groundwater to be submitted with the CAP. The calculated hydrocarbon mass was not included in the CAP. Submit the mass calculation including estimated masses of adsorbed, absorbed, and dissolved hydrocarbons that will be addressed through the proposed corrective actions, and the percentage of the mass that will be removed. The CAP proposed extracting 100,000 gallons of impacted groundwater that may collect in the excavation after backfilling with pea gravel. Depth to groundwater measured at NIW-2 during the last reported groundwater monitoring in September 2001 was 12.59 feet bsg. It is unknown if significant amount of groundwater would be produced if the excavation ends at 12 feet bsg. The vertical extent of the groundwater contamination is not known. Historical groundwater low in the general area according to San Joaquin County Flood Control publication Line of Equal Depths to Water in Fall 1987 was approximately 35 feet to 40 feet bsg. The vertical extent of the impacted groundwater must be delineated or a hydro-geological model developed to demonstrate the practical vertical extent of impacted groundwater. The 2000-foot well receptor survey included in Summary Report ofAddztzonal Subsurface Investigation dated November 9, 2000 identified 8 wells identified in the area. Of the 8 wells, only one is a domestic drinking water well and another an irrigation well (#1 and#8 wells, respectively, on Figure 4 of the survey),with the remaining 6 wells being shallow monitoring wells. The domestic well is reported to be approximately 1,300 feet from the site. It is unknown what pumping influence of these two wells or any other pumping wells might contribute to the vertical migration potential of the groundwater plume. The CAP included Human Health Risk Assessment Study (HHRA) as a remediation alternative for feasibility evaluation. Please be aware that HHRA results are only regarded as one factor during site closure consideration and are not adequate on a stand-alone basis to justify site closure.