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_ „_ The rock units making up the FICCallurn Anticline and the Johnny Moore Syncline have been eroded and then capped by a thick gravel terrace. The [!gland Terrace Deposits consist of river alluvium which was deposited when the Canadian and Pfichiyan Rivers were at an elevation of 8200 feet. The Upland Terrace Deposits have since become eroded as the Canadian River and its tributaries (e.g., Bolton Draw) have become incised. These deposits have sufficient permeability to store and transmit water. Ground water in this aquifer i.s under unconfined water table conditions. Recharge to this aquifer is primarily through infiltration during snowmelt and during sporadic precipitation events. Cround water within these deposits flow down along the contact between the permeable terrace deposits and the bedrock. Springs and seeps develop where this contact has been exposed by headward eroding streams. One such spring has been identified in an area adjacent to the tJyominy Fuel mine on a small tributary of the North Fork of Bolton Draw. This spring feeds a small. pond used for stock and wildlife watering. During mining, this spring will not be affected since this spring is located outside the permit botvrdary and upslope of the mining operations, No wells are located within the Upland Terrace A^poslts. Bolton Draw contains alluvium, recent streamlaid deposits. The alluvium has been mapped by Wyoming Fuel on Exhibit C-2, Appendix C. This map shows the beginning at the confluence of the North Fork with the Afiddle Fork of Bolton Draw at the south- east corner of the permit boundary. Wyoming Fuel has installed an alluvial monitoring hole, Well H2, in this area. Ground water quality samples taF:en from this well are high in total dissolved solids (T DS) and arc of a sodium sulfate type. No water wells are completed in the Bolton Draw alluvium. The high TDS, 7220 mg/1, and high sulfate, 2390 to 4030 'mg/1, sevez•ely restrict the beneficial use of the- Bolton Draw alluvial ground water for irrigation or stocY. r.~ateriny. Following mining, a new aquifer will be created within the spoils. The spoil aquifer will be recharged by water from faults encountez'ed during mining, and through infil- tration and deep percolation of surface water. Both of these sources are closely linked to snowmelt and to a lesser degree infrequent precipitation events. [dyoming Fuel has conducted an infiltration study in and near reclaimed areas of Pit 1. At site 1, the reclaimed spoil area yielded an infiltration rate of 2 inches per hour, and at site 2, an undisturbed sandy loam adjacent to the reclaimed area yielded an infiltration rate of 14 inches per hour (Appendix C, pages 100-104). The lower infiltration rate over t7re spoils was attributed to a mixing of topsoil types, Coal- mont and Fluetsch. The initial infiltration rates in the reclaimed areas are expected to be lower than the pre-mining conditions. A monitoring well, [dell b7, has been completed within the spoil. A water quality sample from this aquifer indicates that the spoil water is shifted from a sodium bicarbonate type to a sodium sulfate type. A single sample from the spoil well is, however, inconclusive. B. Hydrologic Consequences of h[ininy - Ground [Dater During mining, Wyoming Fuel will lower the ground water levels within the Sudduth coal seam, the overburden, and the underburden, and in faulted area water levels in the Sandy Member of the Pierre Shale. The inflows into the pit are not expected to exceed 1 gpm in Pit 1 and 1 gpm in Pit 2, owing to the tightness of these formations. These inflows will not affect aquifer discharges r,~ithin the permit and adjacent areas since no wells are completed within these strata and no sp.rinys eminate from these strata.