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RULE 2 - PERMITS <br />• Faulting in the permit area occurs as normal faults that strike northwest to east -west. The <br />faults are of a regional character and are north and outside of the planned underground <br />operations. Map 2.04.5 -M1, Regional Geology and Hydrology, shows the northern <br />bounding fault zone. The nature of the fault geometry within the mineable portions of the <br />Hayden synclinal basin have made it difficult to accurately predict small displacement <br />faults (where seam thickness is six feet or less) within a virgin mining district. Several <br />attempts have been made to use seismic methods to map the lateral fault traces. <br />Interpretation of the available seismic data to date has not yielded an accurate tool for <br />identifying faults with small offsets. The seismic data, however, have greatly improved <br />the overall mapping of larger structures, which is reflected in the PSCM reserve limits. <br />Aquifer testing was conducted at nine wells in the permit area to determine the hydraulic <br />properties of the overburden, coal and underburden units. The results are summarized in <br />Table 2.04.7 -T2. All but two of the aquifer tests were performed using slug test methods <br />due to the very low hydraulic conductivities in the water bearing units of concern <br />(Oldaker, 2009). The two exceptions were wells COV23 and CWUB23 where constant - <br />head methods were used due to artesian conditions which created flows sufficient to allow <br />accurate measurement (well CW23 was also flowing under artesian pressure, but at a rate <br />too small to accurately measure). <br />All nine wells were drilled using a rotary drilling rig. Water was used for drilling wells <br />• CW2701, COV2702, CW2632 and COV2633 during 1985. Clear water mixed with a <br />liquid polymer viscosifier was used to drill wells CWU13, CWU14, COV23, CW23 and <br />CWU23 during 2008 in order to bring cuttings to the surface and provide strong hole <br />cleaning. Potassium chloride was added to the fluid in order to stabilize the thick shale <br />sequences (Lewis Shale) encountered during drilling, and to prevent swelling and <br />agglomeration. Caliper logs collected on all new wells indicate the holes were within <br />gauge to slightly large through screened intervals. Wells CW23, CWU23, COV23, <br />CWU13 and CWU14 are constricted inside 5 -5/8 inch diam boreholes, with 2 -inch inside <br />diameter steel casing and screen, silica sand filter pack opposite the screened interval, a <br />bentonite annular seal above the filter pack, and a cement annular seal from the top of the <br />bentonite to the land surface. Wells COV2633, COV2702, CW2632 and CW2701 are <br />completed with 1.5 -inch inside diam steel casing and fiberglass screen inside 5 -1/8 inch <br />diameter boreholes, with open hole opposite the screen and cement annular seals from <br />slightly above the screens to the land surface. Each of the nine wells was developed <br />rigorously before conducting aquifer tests. Well development consisted of using <br />pressurized nitrogen gas to remove the entire water column (casing volume). This method <br />was implemented at wells CW2632, COV2633, CW2701, COV2701, CWU13 and <br />CWU14 on at least five separate occassionas before conducting tests. Using the same <br />method, a minimum of 2 casing volumes were removed from wells CWU23, CW23 and <br />CWU23 shortly after completion in November 2008. <br />The slug tests involved used a chain (well CW2632) or a poured -water slug (wells <br />CWU13, CWU14, CW2633, CW2701 and CW2702) to produce a head change of <br />• approximately 20 feet. Water used to conduct the poured -water slug tests was pre- <br />packaged distilled water purchased locally. Well CW23, which was flowing at the <br />surface, but at a rate too small to accurately measure, was slug- tested by removing <br />approximately 183 feet of the water column using pressurized nitrogen gas and measuring <br />PSCM Permit App. 2.04 -47 Revision 03/05/10 <br />