SITE INFORMATION AND CORRESPONDENCE_FILE 1

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Excerpts cin Ground Waters and Site Cleanup Page 16 from the'Nater Quality Control Plan iv. The discharger has demonstrated that no significant pollutant migration will occur to other underlying or adjacent aquifers; v. Ground water pollutant concentrations have reached asymptotic levels using appropriate technology; vi. Optimization of the existing technology has occurred and new technologies have been evaluated and applied where economically and technologically feasible; and vii. Alternative technologies for achieving lower constituent levels have been evaluated and are inappropriate or not economically feasible. j. Soil Cleanup Levels For soils which threaten the quality of water resources, soil cleanup levels should be equal to background concentrations of the individual leachable/mobile constituents, unless background levels are technologically or economically infeasible to achieve. Where background levels are infeasible to achieve, soil cleanup levels are established to ensure that remaining leachable/mobile constituents of concern will not threaten to cause ground water to exceed applicable ground water cleanup levels, and that remaining constituents do not pose significant risks to health or the environment. The Regional Water Board will consider water quality, health, and environmental risk assessment methods, as long as such methods are based on site-specific field data, are technically sound, and promote attainment of all of the above principles. k. Verification of Soil Cleanup Verification of soil cleanup generally requires verification sampling and follow-up ground water monitoring. The degree of required monitoring will reflect the amount of uncertainty associated with the soil cleanup level selection process. Follow-up ground water monitoring may be limited where residual concentrations of leachable/mobile constituents in soils are not expected to impact ground water quality. I. Remaining Constituents Where leachable/mobile concentrations of constituents of concern remain on-site in concentrations which threaten water quality, the Regional Water Board will require implementation of applicable provisions of Chapter 15. Relevant provisions of Chapter 15 which may not be directly applicable, but which address situations similar to those addressed at the cleanup site will be implemented to the extent feasible, in conformance with Title 23,CCR, Section 251 l(d). This may include,but is not limited to, surface or subsurface.barriers or other containment systems, pollutant immobilization, toxicity reduction, and financial assurances.