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' Jerry Lile ' December 10, 2003 Page 5 constituent were also detected in monitoring well TW-2. The footnotes in Table 3, ' "Groundwater Analytical Results for Monitoring Well Samples", identify that the groundwater sample collected from TW-2 on 9/14/98 was filtered using a 0.7 micron glass filter prior to implementing EPA Method 8270 SIM for PAH analysis. ' Consequently, these data, the only monitoring well data from petroleum impacted groundwater, are unacceptable for use in the human health risk evaluation. Subsequent sampling events did not include TW-2 sampling for analytical chemistry ' due to sheen observed on the groundwater. Nonetheless, PAHs were detected from TW-2, though the results are likely an underestimation of the PAH concentrations in the groundwater. ' c. Tablet: Groundwater Analytical Results are to include results of all detected chemicals, and method blank data if contamination was found in the method blank. Data in the August 1998 `Soil and Groundwater Investigation and Site Status ' Report"demonstrate that naphthalene and phenanthrene were not detected in water at similar concentrations in the method blank and sample GB-1; the analytical data report reveals the concentrations detected in GB-1 are over 10-fold higher than the ' method blank. Accordingly, naphthalene and phenanthrene results are to be included in Table 2 and carried through the quantitative human health screening evaluation. ' SPECIFIC COMMENTS— Human Health Screening Risk Evaluation: 1. A conceptual site model is needed. 2. Pages 3 and 4: Evaluation of risks to a hypothetical residential receptor is not conservative enough to over predict or.even protect construction workers because the exposure factors vary. Although carcinogenic risks to residents will exceed risks to construction workers, non-carcinogenic hazards will be greatest for construction workers. Categorically the construction worker's average daily exposure to non- carcinogens is higher, and therefore the estimated potential hazard index is higher for the construction worker. Since construction workers' exposure assumptions result in exposures less than 2 orders of magnitude greater than residential exposures, if the total residential hazard is 0.01 or less, then hazard to construction workers is not ' expected to exceed the acceptable screening level of 1. It should be noted that the screening level human health risk evaluation, although unacceptable to HERD at this time, estimated a total hazard index of 0.03. ' 3. Indoor air exposures were not evaluated, however the data collected thus far do not suggest the need to quantitatively evaluate risks from indoor air exposures. 4. Toxicity Criteria