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Mr. Marshall Cloud October 5, 2007 Page 2 A screening risk assessment for dieldrin was completed by Defense Logistics Agency (DLA) dated March 1, 2007. The screening risk assessment was intended to follow the agreed upon decision logic approved by all agencies and captured in an e-mail from USEPA project manager dated January 30, 2007. The DLA's screening risk assessment was deemed incomplete by the regulatory agencies because it did not calculate the maximum human health risk using the maximum concentration of dieldrin detected. DTSC's Human and Ecological Risk Division (HERD) completed its own risk assessment dated April 24, 2007. HERD's risk assessment calculations used the same ground water data along with the highest concentration of dieldrin of 0.19 pg/L and resulted in a human health cancer risk of 2E-4, with a non-cancer index of approximately 1.6. The resulting cumulative human health risk for dieldrin was outside of the risk management range and therefore necessitated land use controls to limit future exposure pathways as agreed to by all stakeholders. DTSC has a 10-6 point of departure and requires Institutional Controls (ICs) for any remedy that leaves waste in place exceeding levels appropriate for unrestricted use. An ACL for dieldrin above 0.002 pg/L would trigger ICs, in addition to engineering controls, if needed. Raising the ACL to the upper end (10-4) is not protective of potential future uses of the Aquifer, furthermore neither the State nor the USEPA can impose land use controls on the Alvarez private property, the land owners under which the plume has migrated without their consent. In the case of DDJC-Tracy, the U.S. Government has impacted future land uses of and possibly the value of the neighboring property and requests to raise the ACL for dieldrin appears to be an attempt by the U.S. Government to dilute its liability. Conclusion DTSC cannot support raising the ACL for dieldrin at DDJC-Tracy because it would not be protective of human health and the environment moving forward. However, DTSC supports developing a TEFA to determine if the current pump and treat remedy for ground water, in addition to current innovative technologies, are unable to remediate dieldrin to the current ACL. If so, DTSC envisions that ICs in the form of land use restrictions coupled with long-term ground water monitoring would be necessary to ensure protection of human health and the environment into the future.