SITE INFORMATION AND CORRESPONDENCE

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6. Mass balance calculation of the subsurface treated versus that remaining, 7. Technology used to clean the site; if Best Available Technology (BAT) was not used, explain why, S. Zone of influence calculated for the subsurface remediation system and zone of capture attained for soil and ground water remediation system,' 9. Reasons why"background " was/is unattainable using BAT, and g g � s 10. Rationale why conditions remaining at the site will not adversely impact water quality, } health, or other beneficial uses. 3 As part of RTDs review of the Closure Evaluation Report din comparison to the Appendix B r guidelines, RTD has prepared Table 1 which identifies where in the subject report the information requested is located. Based on RTDs review/comparison as' shown on Table 1, the only item missing is a map showing underground utilities. RTD has obtained underground utility location information from the California Water Company (water main0aterals), the City of Stockton, and the East Stockton Sanitary Sewer District (sewer mains/laterals). A map showing the location of these underground utilities is shown in Figure 1. Due to the' fact that the extent of historic soil impacts was very well defined and limited to an area between the', former USTs and the pump islands, the location of underground utilities in Waterloo Road and Report Avenue would not be affected by the release of petroleum hydrocarbons. RTD has reviewed the Closure Evaluation Report with respect to content. The report, data, figures, and calculations are in agreement and the conclusions drawn are reasonable. RTD calculated excavated mass of diesel and gasoline removed during, UST replacement activities. RTD also calculated the mass of diesel and gasoline remaining in soil. RTDs estimations are in close agreement with those contained in the Closure Evaluation Report. MERITS OF SITE C RTD concurs with the recommendation for site closure contained in the Closure Evaluation Report. It has been estimated that at least 85-percent of the'petroleum hydrocarbons have been removed from the site. Soil sampling conducted shows that pthe hydrocarbon impacts to soil is limited in horizontal and vertical extent. Excavation activities were conducted to the maximum extent practicable given limitations due to the proximity to existing structures. The remaining 'Al hydrocarbon impacts to soils are of limited extent and low` volume. Further active remedial activities to remove the remaining hydrocarbons in soil is not economically feasible, nor will result ` in any benefit to human health or the environment. Previous groundwater sampling conducted when groundwater levels were approximately 40-feet below grade indicated very minor concentrations at levels close to detection limits. Given thatnearly all of the soil impacts have been removed, future impacts to groundwater (i.e.- if groundwater levels return to 35- to 40-feet below grade) are not likely. 4`` } Further expenditure of money and energy on this site will needlessly divert limited human and economic resources available to Ultramar, SJCPHS and the?RWQCB from other unauthorized releases that require corrective actions necessary to protect human health and the environment. SJCPHS RESPONSE F,VALITATION ti In a letter dated February 24, 1995 to Ultramar from SJCPHS, it was stated that the Closure Evaluation Report failed to provide all the technical information requested to evaluate the site for closure. In an effort to find out what information requested was missing from the Closure Evaluation Report, Ultramar sent a letter dated March 21, 1995 to SJCPHS asking for F clarification in this matter. SJCPHS responded to this request by sending an excerpt of the - 2 -