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M. Scott Mansholt -3 - 14 July 2005 <br /> ChevronTexaco <br /> Mountain House Site#2 <br /> Based on our review of the findings we have the following comments: <br /> • According to the soil logs, depth to water ranged from 13 feet to 17.5 feet. However, soil <br /> samples were obtained from each boring at 2 and 6 feet; the next sampling intervals were <br /> between 20 and 44 feet. Regional Board staff concurs with risk assessment recommendations for <br /> residential scenarios that soil samples need to be taken at regular intervals in the upper 10— 12 <br /> feet for analysis. Therefore, additional soil sampling is needed. <br /> • The report, Figure 3, and Table 1 analytical results indicate that soil samples at 2 and 6 feet have <br /> been impacted by petroleum hydrocarbons; however, the summary/conclusions on page 6 states <br /> that affected soil occurs at 15 to 36.5 feet. Clarification of this inconsistency is needed. <br /> Overall, based on review of the findings, it appears that impacted soil and groundwater has been <br /> delineated and is limited in extent to beneath Byron Road. However, removal of impacted soil <br /> containing elevated concentrations of hydrocarbons may not be feasible given that the majority lies <br /> beneath Byron Road. <br /> Regional Board staff cannot make any final determinations until a human health risk assessment has <br /> been reviewed by OEHHA. <br /> By 15 August 2005 please provide written clarification for the items discussed above. <br /> If you have any questions or comments, please contact Dean Hubbard at (559) 445-5179. <br /> SHELTON R. GRAY C. DEAN HUBBARD <br /> Senior Engineering Geologist Engineering Geologist <br /> RG No. 6357 <br /> CC' Michael J. Infurna, San Joaquin County EHD, Stockton <br /> Eric Ted-Bose, Trimark Communities, Tracy <br /> Jeff Willett, Condor Technologies, Stockton <br /> Luis Mercado, SAIC, Sacramento <br />