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f <br /> ATTACHMENT <br /> REVIEW OF MODIFIED.CLOSURE PLAN, KEARNEY-KPF, SAN JOAQUIN COUNTY <br /> Page-6. The analytical results from the split samples collected by the <br /> Department of Health Services (DHS) should also be used to determine <br /> whether or not the heavy metal concentrations in the soils exceed <br /> their respective soluble designated levels (SDLs) . <br /> Page 8. The proposals to remove the soils which exceed the SDLs, dispose of <br /> these soils at a Class I facility and perform confirmation sampling <br /> are acceptable. However, the proposal to cover the wastes is <br /> unnecessary because the soils to be closed in-place have been <br /> determined through sampling and analysis, not to pose a threat to <br /> water quality. After confirmation sampling the facility must grade <br /> the area to divert drainage away from the ponds to minimize <br /> infiltration from precipitation. <br /> Page 8. The vertical criteria for the volume of soil to be excavated for <br /> disposal should be the same as the horizontal criteria. This would <br /> require that the height of the cylinder of soil to be removed would <br /> be half the distance to the next lower soil sample not requiring <br /> remediation; rather than the exceeding the soil sample depth by one <br /> foot. However, the difference between this recommendation and the <br /> Hargis proposal in the height of the soil cylinder to be removed, is <br /> only a few inches. <br /> Page 9. Because the contaminant concentrations in the soils to be closed in- <br /> place are below the SDLs but above background concentrations, the <br /> installation of the cover over the surface impoundments is not <br /> required by Subchapter 15 and these disposal areas will not be <br /> permitted as Subchapter 15 units. <br /> Page 9. The report states that the installation of a cover over the surface <br /> impoundments, although not required by the Resource Conservation and <br /> Recovery Act (RCRA) , will minimize potential leaching by rainfall <br /> infiltration and will eliminate the potential for human contact with <br /> contaminated soil . It is also suspected that the cover offers an <br /> alternative to stockpiling the soils which must be excavated for <br /> construction of the infiltration basin. <br /> Page 9. The plan states that the slope of the cover will range between one <br /> and two percent. A one percent slope is not recommended as it may <br /> not prevent ponding during periods of rainfall . <br /> Page 9. It is unclear why a sand blanket with a vent to the atmosphere was <br /> included in the design of the cover. The wastes to be closed in- <br /> place are not anticipated to produce methane. <br /> Page 10. If closure of the surface impoundments begins as proposed in <br /> September 1990, then the closure of the units will proceed without <br /> revision of the waste discharge requirements (WDRs) . <br />