2016-10-27_PERMIT FILE - C2009087A (2)

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