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INTERNATIONAL TECHNOLOGY CORPORATION Ms Mary Maeys 6 January 15, 1996 At Location 1 (basement) Analysis indicated 0 63 TOM (silty sand) 0.63 TOM/1 724 = 37% (fraction organic carbon) At Location 2 (sidewalk) Analysis indicated 0 19 TOM (sandy silt) 0.19 TOM/1 724 = 11% (fraction organic compound) The higher the fraction of organic compounds (foc) used in modeling, the later the contaminant spikes occur and the lower the absolute value of the spikes. In order to be conservative lower foc's were used during modeling, in order to observe the maximum contaminant spikes expected. Issue B Provide evaluation of each soil type versus the measured carbon concentration ' Response B Th h m f v for l f % Our analytical p• se c V-Etat ilial sifts an •c alit • loamy sant • 35 y data for the silty sand collected at Location 1 indicated an foc value of 37% An foc value of 30% is listed for loam in the V-Leach manual Our analytical data for the sandy silt collected at Location 2 indicated an foc value of I I% V. Report References Issue A Provide a list of references Response A reference section is provided m Appendix E of the IT Corporation "Recommendation for Site Closure Report," April 1995 SUMMARY/CONCLUSIONS In conclusion, the above letter provides all additional information, requested by the San Joaquin County representative in August 1995, in order to initiate closure actions at this site A review of this data indicates the IT has consistently applied conservative assumptions during calculation of residual diesel contamination and during modeling, in order to predict the potential impact to groundwater by the inplace residual diesel fuel Results of our modeling efforts indicate that after a 50 year period, the MCL's for ethyl benzene and xylene and the SNARLS for diesel fuel will not be exceeded in groundwater It therefore appears that little to no risk to human health or the environment remains associated with the residual diesel fuel at either former UST location. In light of recent State Water Resources Control Board and Regional Water Quality Control Board support for closure of "low risk" UST sites, it appears that a closure recommendation for this site is warranted.