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pretreatment needs, not injection needs.) <br /> 12. Section 2.3.2.6 indicates that the position of the water table will guide placement of <br /> the injection well shut-off controls. Whereas, the position of the ground surface <br /> relative to the injection mounding level seems to be more important to the well shut- <br /> off controls than the static water table level, at least for injection wells in the Upper <br /> Horizon. <br /> Please explain the design criteria for controlling injection levels, depending on <br /> whether the injection horizon is unconfined or semi-confined. <br /> 13. Section 2.4.2.3: Infiltration tests at proposed sites for spreading basins or infiltration <br /> galleries are worthwhile. Since the test adds water to the unsaturated zone, we <br /> recommend performing constant head tests rather than falling head tests, which will <br /> provide more reliable analysis results. <br /> We recommend deleting the reference to falling head tests. <br /> Please explain the "box" infiltration test method. Does this follow a standard <br /> method? <br /> 14. Section 2.4.2.3 proposes infiltration tests for spreading basins and infiltration galleries. <br /> The performance of existing unlined ponds may provide an additional source of data <br /> on local infiltration rates. <br /> Water balance analyses of existing ponds should be included in the pre-design <br /> work, if not already available. <br /> 15. Section 3.2.2.2 states that the current IRM system has exceeded the ROD-established <br /> effluent limit for dieldrin. Note that NCP Sections 300.68(1) and 300.435(b) require <br /> compliance with ARARs during the course of RD/RA. However, the text is silent on <br /> what actions will be taken to prevent future excursions over the established limit. <br /> Per the NCP requirements to comply with ARARs during RD, please include <br /> text which would provide assurance that the dieldrin standard will not be <br /> exceeded in the future. <br /> 16. Section 3.2.2.2 states that should other injection approaches be considered during <br /> design, "regulatory effluent treatment standards may have to be revised." This <br /> statement is not understood. <br /> Please explain more thoroughly why it is believed that injection approaches <br /> would impact regulatory effluent treatment standards. <br /> EPA/I IIAN94 4/6 <br />