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Siltstone is normally considered a poor conductor of water because of its finegrained nature. Sandstone, <br />on the other hand, can make a prolific aquifer if it is clean and rather poorly cemented. However, <br />• according to the above description, sufficient fines and cement are present in the lease area sandstones to <br />clog the pore spaces, resulting in extremely low transmissivities and other yield properties. <br />A fourth potentially different hydrologic zone in the lease and adjacent areas is the alluvium of the White <br />River and its tributaries. The White River has a fairly well developed flood plain, showing the distinct <br />meander patterns of a braided stream. In the vicinity of the lease area, the White River alluvium contains <br />pea gravel and gravel up to an average of 3/4-inch in diameter. In addition the alluvium contains sand, silt, <br />and clay-sized material derived from the Mesaverde and other upstream formations. This unconsolidated, <br />very fine material has caused the alluvium to be much less permeable than would normally be expected <br />and, when saturated, has been noticed to flow or move (a "quick" condition that makes completing a well <br />particularly difficult). Drilling in the alluvium of the White River indicated a maximum depth to bedrock of <br />37 feet, the lower 22 feet of which was a gravel, sand, silt and clay mixture with the rest being all fine silty <br />and clayey material. <br />II.C.3.c Field Test Operations Little was known about the subsurface hydrologic system of the lease <br />and adjacent areas when exploration drilling began in 1978. No reports on the hydrology of the specific <br />area were available, and only two long-abandoned water wells existed in the area, located in and adjacent <br />to the alluvium of the White River near the mouth of Scullion Gulch. <br />• Because of this lack of hydrologic information, athree-phase groundwater program was developed. <br />Phase 1, from the fall of 1978 to July of 1979, consisted of participating in the 1978 exploration drilling <br />program to glean hydrologic information from the drill and core holes. During this phase of the program, <br />geophysical and geological logs of the area were studied to determine the existence of hydrologic zones. <br />Reconnaissance aquifer tests were also completed to determine the feasibility, reliability and necessity of <br />future testing operations. During July and early August, 1979 all the information obtained to that point was <br />evaluated, and atwo-part program (Phases 2 and 3) of drilling and aquifer testing was designed, approved <br />by the appropriate authorities and implemented. Phase 2 provided for drilling selected observation and <br />test wells, water quality sampling and aquifer testing. Phase 3, which was implemented upon the <br />evaluation of Phase 1 and Phase 2 data, consisted of drilling additional holes at selected locations. In <br />addition, during the course of Phases 2 and 3, water level measurements were made on all exploration <br />holes that had been cemented through the coal zone but not yet filled with cuttings and reclaimed. These <br />data were initially used to determine the length of time necessary for water levels in the area to stabilize <br />and to construct the initial potentiometric surface map for the Upper Sandstone Facies. More recent data <br />are now used to construct the potentiometric surface maps <br />Figure II.C-24 gives the location of all holes in the area from which hydrologic data were initially obtained <br />or measurements attempted (i.e. dry holes). Location, elevation, and other pertinent information are <br />contained in Attachments C, D and E for the test and observation wells, the cemented but unfilled <br />exploration holes and the dry holes in which measurements were attempted, respectively. <br />i Permit Revision #6 (3/2008) II.C-51 <br />