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Mr. Jerry Lile `� �•/ <br /> October 2, 2001 <br /> Page 3 <br /> Specific Comments <br /> 1. The current investigation reports three previously unreported constituents in the groundwater: <br /> toluene and 0.7 µgl, xylenes at 1.5 µg/I and phenanthrene at 0.2 µg/I. These constituent con- <br /> centrations were added to the risk assessment. The revised risk assessment calculation indi- <br /> cated that the theoretical excess cancer risk was 1 x 10$ and the hazard index was 0.65. <br /> 2. The consultant did not explain the significance of the finding that the silica gel procedure re- <br /> sulted in greater TPHd detections in samples GMX-23-GGW and GMX-24-GGW. The boring <br /> log for sample GMX-28 does not show the sample depth. The text should be revised ap- <br /> propriately. Figure 2 has the GMX-23 results table in two (2) locations. <br /> 3. HERD reproduced the risk screening calculations. The risk calculated for the property was <br /> at 1 x 10'6, which is within the range that is, considered acceptable (1 x 10-6 to 1 x 10-4). The <br /> risk calculations were based on the use of the equivalent of"J" qualified (estimated) data. <br /> The risks were calculated for a hypothetical, future resident at the site. <br /> 4. In attachment #3 of the addendum - Exposure Parameters and Constants. Under the inha- <br /> lation of volatiles in air, the intake rate (inhalation) is listed as L/d 2 for adults and 1 for <br /> child. These values are incorrect. <br /> Conclusions and Recommendations <br /> The analytical data supporting this investigation appear adequate both in quantity and quality. <br /> Detection limits were sufficiently low to support the intended end-use of the data. The screening <br /> risk evaluation used the methodology and equations presented in the PEA. <br /> The residual levels of petroleum-related hydrocarbons in the soils and groundwater beneath the <br /> site are below levels that would constitute an unacceptable risk to human health and the envi- <br /> ronment as evidenced by a cancer risk of less than 1 x 10-6 and a hazard index of less than 1.0. <br /> This meets the criteria for a "no further action" determination as outlined in the PEA manual. <br /> Please contact me at [(916) 255-6626] or e-mail at dberry@dtsc.ca.gov if you have any ques- <br /> tions regarding the evaluation of the above document. <br /> Reviewed by: Stephen DiZio, Ph.D. <br /> Senior Toxicologist, HERD <br /> I <br /> j <br />