2010-05-07_PERMIT FILE - C2009087 (6)

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the eastern limb of the anticline. Dips on the eastern limb are commonly 30 degrees to 60 degrees; those on the western flank are approximately 10 degrees to 25 degrees (Robson & Stewart, 1990; • Peabody Coal Company, 1980). The relation of the coal bottom structure to the Hayden Creek Syncline and its shared limb with the Tow Creek Anticline is presented on Map 2.04.6 -M5, Wadge Bottom Structure (confidential). The nature of the fault geometry within the mineable portions of the Hayden synclinal basin have made it difficult to accurately predict small displacement faults (< seam thickness of six feet) within a virgin mining district. Several attempts have been made to use seismic methods to map the lateral fault traces well in advance of mining. Interpretation of the available seismic data to date has not yielded an accurate tool for small offsets. The seismic data, however, has greatly improved the overall mapping of larger structures which are reflected in the PSCM reserve limits, Map 2.04.6 - Ml, Surface Geology. The mapped structural features in the northern portion of the underground workings are rolls that transition into small displacement faults outside of the mine workings area. Three faults north of the mine workings area, along the permit boundary are believed to have significant displacement. No fault displacement has been detected at the seam depth in the planned mine working area. Interpretation of Overburden and Coal Geochemical Data Roof, floor, and interburden (if applicable) samples were collected, composited, and analyzed consistent with the Colorado Guidelines for Collection of Baseline Water Quality and Overburden • Geochemistry Data, issued September 16, 1982. Analysis results are summarized in Table 2.04.6 - T1 and in Exhibit 2.04.6 -E3, Geologic Information — Overburden and Coal Quality (confidential). The analytical results were compared with the overburden suitability ratings developed by the Wyoming Department of Environmental Quality (WDEQ) as Guideline Number 1 to identify any potential limitations or concerns relative to aquifer restoration considerations given the final underground location of those materials. The following sections summarize the analysis results relative to applicable overburden suitability criteria for the key parameters. pH - The average pH value was found to be 8.13, with a range from 7.7 to 8.4. According to WDEQ Guideline No. 1, the aquifer restoration suitability of these roof and floor materials would be rated good, as shown on Table 2.04.6 -T1. Based on a total of 10 samples, pH analysis results for the roof and floor materials indicate no problems relative to revegetation or water quality. Electrical Conductivity - The average electrical conductivity of the roof and floor samples was 1.68 millimhos per centimeter (mmhos /cm) with a range of 0.46 to 2.6 mmhos /cm. The electrical conductivity values represented by these data fall within the lower range for normal soils and do not indicate any potential reclamation or aquifer restoration problems. Boron - The average boron concentration was found to be 0.4 milligrams per kilogram (mg/kg) with a range of 0.2 to 0.07 mg/kg. According to the WDEQ guidelines, boron values fall within the reclamation suitability value of <5.0 mg/kg. No potential problems with boron are anticipated. • PSCM Permit App. 2.04 -29 6/15/09