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Jeff Van Slooten Page 4 November 29 , 1989 level of 7 . 9 mg/ml. Errors of this sort must be corrected in order to make a correct assessment of potential health hazards. Since this document will be a matter of public record, it is very important that data be presented in a manner that will allow the public to have confidence in the information. In this same part of the report, it is stated that PCP levels in storm water have decreased over time due to changing procedures. However, the values on Table 3-8 still show a great deal of variability. Are there data for 1988 and 1989? The text (RAP 4-8) discusses further reductions in PCP discharges in 1989 but the data do not appear to be presented in the report. This document should "stand alone" and include, or reference, all data needed to characterize the site and its potential hazards. 6 . PCP is considered by the DHS to be a carcinogen (see Toxic Substances Control Program Scientific Guidance Memo 89-3) and must be addressed as such in the assessment of risk. Chromium VI (PHA 5-7) is considered by EPA to be a carcinogen by the inhalation route. This will require that all estimates of excess cancer risk be recalculated. The text PHA, page 3-5 , states that pentachlorophenol (PCP) was detected at 0. 010 mg/1 in OSSB near Gold Bond. Data to support this could not be located in the current PHA. 7 . All routes and all chemicals must be sunned (for the same toxic endpoint) in order to determine total risk to the biological receptor. 8 . It is very difficult to follow the rationale used in calculating the excess cancer risk and the comparison of the estimated daily intake to the reference dose (Tables in Appendix C of the PHA) . Text Tables 3-1 through 3-7 present the arithmetic mean concentration of chemicals in the soil. However, in Appendix C the geometric mean is used. What is the rationale f---- this? orthis? It seems that based on the range of sample concentrations, either the arithmetic or geometric mean should be used throughout the document. All chemicals that are identified in the soils are not found on the Tables in Appendix C. Specifically, chromium does not appear on any table in Appendix C, however, it is present in virtually all soil areas. Tables 6-1 through 6-4 present the excess cancer risk using the mean concentrations only. The maximum values should also be presented.