SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

standards, and do not pose an unacceptable risk to human health or the environment. Table 4-3 itself should be revised as follows: a. The language in the box explaining the SESOHJVLEACH Modeling Results for Dieldrin should be modified as follows: "Modeling results indicate the maximum concentration of Dieldrin in groundwater is leas than will not exceed the beneficial use limit(0.002 ug/L), which is less than the aquifer cleanup standard of 0.5 ug/I.." b. The box for DI WET Analysis performed for DDT should be modified to include the fact that there is no aquifer cleanup standard for DDT and to provide information about the likely concentration of DDT in groundwater from soil contaminated with 47 mg/kg of DDT (the actual maximum remaining concentration). Finally, unless the DLA can demonstrate that the DI WET test can be interpreted to mean that the likely result of a DI WET test on soil containing 47 mg/kg would be below beneficial use limits, nothing in the ESD appears to justify the conclusion in Table 4-3 that residual DDT contamination is unlikely to impact groundwater quality. The text in Section 4.1.2.5 does not say anything about this, and Table 4-3 only says that SESOIL and VLEACH simulations suggest that DDT won't reach groundwater for 50 to 100 years. Again, it is not sufficient to demonstrate that the remedy is protective of groundwater. NEW GENERAL COMMENTS 1. It appears that all rounds of responses to comments on the Draft ESD that occurred between the submission of the Draft ESD and Draft Final ESD are not included in the RTC table at the end of this document. EPA's comments dated March 3, 2004, which were submitted electronically, were missing from the RTC table. Documentation is an important part of the CERCLA process and it is important that decisions agreed upon by DDJC and the regulators can be followed and are documented for the Administrative Record. Please include all RTCs in the next version of the ESD. 2. The decision logic used for the SWMU 8 proposed cleanup standard for DDT is unclear. It appears that two cleanup levels are proposed,47 ug/kg based on protection of human health and 103 ug/kg based on DI WET results. In addition, the comparison between DDT and DDX is confusing. For example,Table 4-3 on Page 4-5 for DDT states that the residual soil concentration is 47 ug/kg and then proceeds to use the DDX risk-based cleanup standard of 30,000 ug/kg as justification for protection of human health. The text in Section 4.3.6 on Page 4-11 uses an exposure point concentration of 800 ug/kg for DDT as the justification for protection of human health. Please clarify the text and table to clearly state what the new proposed cleanup standards are and clearly outline the decision process and rationale used to revise the standards. In addition, it would be helpful to the reader if the new cleanup standards for dieldrin and DDT were stated in text and/or 2