SITE INFORMATION AND CORRESPONDENCE_FILE 2

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SWO, %W01 contention that detectable concentrations of petroleum hydrocarbons have not and will not impact offsite ground water monitoring wells. Second Bullet Item As presented in our rebuttal of Section 1.2.6.2., Pages 1-7 and 1-8, Second Bullet Item, Paragraph 5, the potential for cross contamination is highly unlikely, and not a legitimate concern. Contaminant distribution in monitoring wells has remained consistent, and does not reflect shifts in contaminant movement deep within the aquifer. Third Bullet Item Alton Geoscience accurately stated that "the concentration of benzene in on-site ground water monitoring wells has historically been low," and disagrees with the Geomatrix contention that the statement is misleading. The Alton Geoscience statement and the analytical results for ground water sampling attest to the accuracy of the statement. Geomatrix refers to the ground water sample obtained from boring B-7 as the basis for their interpretation. However, as was stated previously, the ground water sample from boring B-7 (1) was not a representative ground water sample, (2) was not obtained from a properly installed ground water monitoring well, and (3) did not exclude the possibility of cross contamination from the drill auger or soil. Section 7.0, Pages 7-1 through 7-3 First Bullet Item A work plan was presented to SJC PHS/EHD for comment and/or approval before commencement of field activities. SJC gave approval to the work plan as it was submitted. No changes or additions were made; the plan satisfied the SJC PHS/EHD. Since pre-excavation characterization at the site was adequate, sidewall samples were unnecessary. Residual hydrocarbons within or below the capillary fringe are considered part of the ground water problem. Second Bullet Item Alton Geoscience does not agree with the statement "the risk assessment did not evaluate all appropriate future uses of the property. " Exposure scenarios presented in the risk assessment document and their corresponding assumptions were developed within the context of the following land use classifications: residential, commercial/industrial, agricultural, or recreational. According to the United States Environmental Protection Agency (EPA), "occupational scenarios should be evaluated when land use is (or is expected to be) commercial/industrial." The exposure scenario evaluated in this assessment was selected, in part, on the basis of the proposed development of the Stonebridge Industrial Park. If an alternate land use is proposed for the site, an alternative risk analysis, based on the site-specific 11