SITE INFORMATION AND CORRESPONDENCE

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RE-MANUFACTURING -3- 28 February 1991 CLOSURE PLAN (the indicator parameter) resulting from the SI, because of its close proximity to surface waters. The SI is adjacent to Mormon Slough (to the north) and a surface water drainage channel (to the east) . Does the lead contamination extend to the slough or drainage channel? The proposed cap may not keep water in the slough and drainage channel from coming in contact with residual wastes in the SI. Page 15 of the plan states that the closure design is based on Chapter 15, Section 2582 (b) (1) and (b) (2) , which allows the closure of the SI as a landfill with residual contamination in native soils left in place. Section 2582 (b) (1) states that: " . . If, after reasonable attempts to remove such contaminated materials, the discharger demonstrates that removal of all remaining contamination is infeasible, the waste management unit shall be closed as a landfill pursuant to Section 2581 of this article. . . " We cannot determine if it is infeasible to remove all contaminated soils until the extent of the contamination has been determined. Once the volume of the waste is identified, treatment and disposal alternatives need to be evaluated to determine feasibility of removal of all or portions of contaminated subsoils. It is also possible that the soil surrounding the SI may have been contaminated by other sources. For instance, background sample BG-2 was collected roughly 150 feet east of the SI and contained hazardous concentrations of lead (3720 mg/kg) at 4 feet below ground surface. The question of other contamination sources should be resolved through additional investigations. Section 2582 (b) (2) states, "All residual wastes . . . shall be compacted, and the waste management unit shall be closed as a landfill pursuant to Section 2581 of this article, provided that the closed waste management unit meets applicable standards for landfill waste management units in Articles 3 and 4 of this subchapter. . ." The proposed closure of the SI as a waste management unit does meet these requirements. Closure Plan Deficiencies: 1 . The lateral extent of the soil contamination surrounding the SI must be defined in accordance with the requirements of the HAR. Therefore, additional soil borings are required to determine the lateral extent of the soil contamination and to determine the feasibility of excavating additional soil . 2. The plan proposes to leave hazardous waste in place. Therefore, Chapter 15 requirements for closing a class I SI will have to be complied with or an engineering alternative providing equivalent protection must be proposed. Kleinfelder's proposal to simply backfill an unspecified amount of hazardous waste in place with moderately compacted on-site soils and a 2-inch asphalt cap is unacceptable. 3. To close with residual contamination left in place as a landfill you must: 1) determine the volume of wastes to be left in place and 2) demonstrate that all other alternatives are infeasible. A final closure plan and post closure plan per Section 2593 of Chapter 15 must be submitted as described in Section 2597. 4. Section 2510(b)&(c) states that a discharger must demonstrate that there is a specific engineered alternative that is consistent with the performance goal addressed by the particular construction or prescriptive standard, and affords