PERMFILE119996 - Laserfiche WebLink

Home Browse Search

2.0 Summary of Known or Potential Waste Streams and Proposed Management Prior investigations or visual observations near or in the gravel lease azea revealed the presence of hydrocarbon constituents (benzene) in groundwater in the azea of Oxidation Ponds 1-3; free product (degraded distillate) on the water table in the vicinity of WP-3; stained soils in Oxidation Pond No 1 and the adjacent ditch to the north; a possible asbestos landfill neaz the northernmost corner of the gravel lease azea that also shows evidence of disposal (landfilling) of solid waste. Figure 1 shows the locations of these azeas. Previous sampling locations and analytical laboratory results in the proposed gravel mining azea are presented in the SCP. In addition, the results of the SCP for Subazea 3 revealed the presence of free product in MW-2 and high TPH concentrations in the overburden soil north of Evaporation Pond No. 9. These results aze presented in the Soil Chazacterization Data for Evaporation Pond No. 9 (October 29, 2001) and associated analytical reports. A sepazate plan for the management and disposal of these hydrocazbon-impacted soils during mining is detailed in Appendix A. Subsequently, four additional monitoring wells (MW-4 through MW-7) were installed to define the downgradient extent of free product present in wells MW-2 and WP-3 (Figure 2). MW-4 was installed approximately 200 feet southwest of MW-2 and based on April 2003 data, contains about 4 inches of product on the water table. No product was detected in MW-6, installed approximately 200 feet southwest of MW-4. Thus, the southern extent of product has been defined to be somewhere between MW-4 and MW-6. Well WP-3 also contains about 4 inches of product. Wells MW-5 and MW-7, installed downgradient of WP-3, do not contain product. To reduce the risk of mobilizing the free product present to the north during pumping of groundwater during mining, the mining plan has incorporated the installation of two trenches (Trenches 1 and 2, Figure 2). These trenches will be dug 5 feet below normal groundwater levels and filled with water to provide a positive hydraulic gradient against the groundwater to the north to keep any contamination from entering the mining pit azea. The trenches will be maintained for the life of the mining azea. Construction and operation details for the trenches aze included in the Gilsonite Pit Permit Application. A potential asbestos dump azea is also present in the northern portion of the mining permit area (Figure 2). A 200-foot buffer will be surveyed, staked and maintained azound this dump area, and no mining, excavation or other intrusive activity will take place within this buffer zone. The dump azea is within the Staging Area for the mining operations that will also be covered with approximately 3 feet of clean overburden to provide a safe working azea that can also be later used as an industrial site. Table 1 summarizes waste streams and appropriate management strategies.