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0 <br /> Re-Manufacturing, Ltd. -3- 26 June 1991 <br /> Closure Plan <br /> We assume that the cap proposed in the closure plan will extend to the building south <br /> of the impoundment and that this building defines the southern extent of the surface <br /> impoundment contamination. For the purposes of TPCA, an arbitrary limit to define the <br /> lateral extent of the contamination to the east has been chosen by Re-Manufacturing to <br /> extend to the 18-inch drainage pipe east of the impoundment, with the condition that <br /> Mr. Moore's property outside of the surface impoundment would continue to be <br /> investigated and remediated concurrently with the closure of the TPCA impoundment. <br /> The plan only proposes to investigate the areas east and southeast of the 18-inch <br /> drainage channel . However, on-site contamination does not only extend to the east and <br /> southeast of the impoundment. On 7 May 1991 Board staff collected a soil sample west <br /> of the impoundment which contained 1000 mg/kg total lead. The results are contained <br /> in the May 1991 annual inspection report. The extent of the contamination, as well as <br /> the source in this area must also be dealt with in the expanded site investigation. <br /> It appears that the vertical extent of the lead contamination, however, is limited to <br /> two feet below the current impoundment bottom, with the exception of one sample, which <br /> has a concentration of 611 mg/kg total lead at 5 feet below the impoundment floor. In <br /> order to define the vertical extent of the contamination in this area for the HAR, <br /> further investigation is required. This apparent vertical migration of lead cannot be <br /> dismissed as fill material . Re-Manufacturing must propose how this will be <br /> accomplished. <br /> Impoundment Closure <br /> 1. The impoundment was constructed prior to the effective date of Chapter 15. <br /> Therefore, the impoundment won't meet the siting criteria of Article 3 or the <br /> construction standards of Article 4. Re-Manufacturing proposes to close the <br /> impoundment with hazardous waste in place and cap it using Chapter 15, Section <br /> 2582 (surface impoundment closure requirements) as guidance. In addition, further <br /> investigation of the site east of the impoundment is proposed. <br /> 2. Section 2582 (b) (1) states that if after reasonable attempts to remove <br /> contaminated soils from the impoundment the discharger demonstrates that removal <br /> of all remaining contamination is infeasible, the waste management unit shall be <br /> closed as a landfill pursuant to Section 2581. Section 2581 discusses landfill <br /> closure requirements. Re-Manufacturing proposes to remove all soils above the <br /> BTLV. It would be infeasible to excavate and dispose of all contaminated soils <br /> above what appears to be native background, roughly 5 mg/kg total lead, since <br /> samples have shown that large volumes of lead contaminated soils extend to other <br /> areas of the property and the slough. <br /> 3. The closure plan states that after the final excavation, the remaining impoundment <br /> embankment material will be regraded and compacted within the impoundment for use <br /> as a portion of the foundation layer for the final cover. It also states that <br /> clean make-up soils, approximately 1000 cubic yards, will be imported from an <br /> approved site for additional foundation material . According to Section <br /> 2581(a) (1) , the impoundment embankment materials may be used as part of the <br /> foundation layer for the final cover, provided that the soils have appropriate <br /> engineering properties. The foundation layer shall also be compacted to the <br />