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-ZD- <br />The alluvium of the L'anadian River is coarse-grained and supports agriculture <br />throuyh both subirrigation and flood irrigation. rtecharge to tnis aquifer is <br />primarily from the river and the numerous irrigation ditches which traverse <br />the wide flood plain. The trioutaries and the alluvium of the tributaries <br />which flow through the three mines contribute very little to recharge of the <br />t;anadian River alluvium. This is due to the low contribution of surface flow <br />(Williams Draw flowed for only 60 days in 1980) and the low permeability of <br />the tributary's alluvium. <br />The alluvium of Mann craw is a poor aquifer consisting of fine-grained sand, <br />silt and clay. The alluvium in the area of the Bourg Mine is thin (0 to 20 <br />feet thick) and is restricted to narrow bands paralleling the stream course. <br />The alluvium of Sudduth, 'Williams and Bush Draws contain water table aquifers <br />which are highly variable in their aquifer charactistics. This is due to the <br />lenticular and discontinuous nature of the more permeaole sands and gravels. <br />The ground water in these aquifers has high salinity and total dissolved <br />solids concentrations. The poor water quality is the result of leaching of <br />the marine Pierre Shale in the headwaters of these streams. <br />Bolton Draw contains alluviwn and recent strea~nlaid deposits. This alluvium <br />is fine-grained and contains only 5.4 acres of subirriyated vegetation. This <br />subirrigated area is a perched aquifer which is isolates from a deeper water <br />table aquifer downstream. Recharge takes place during orief periods of runoff. <br />Wyoming Fuel has installed an alluvial monitoring hole, well ~2, in the Bolton <br />Draw alluvium. Ground water quality samples taken from this well are high in <br />total dissolved solids (TDS) and are of a sodium sulfate type. No water <br />supply wells are completed in the Bolton Draw alluvium. The high TDS, 722U <br />mg/l, and high sulfate, 2390 to 4030 mg/1, Beverly restrict the beneficial use <br />of the Bolton Draw alluvial ground wter far irrigation or stock watering. <br />Following mining at the Bourg Mine, a new aquifer will be created within the <br />spoils. The spoil aquifer will be recharged by water from faults encountered <br />during mining, and tnrouyh infiltration and deep percolation of surface <br />water. Both of these sources are closely linked to snowmelt and to a lesser <br />degree infrequent precipitation events. Wyoming Fuel has conducted an <br />infiltration study in and near reclained areas of their Pit 1. At site 1, the <br />reclaimed spoil area yielded an infiltration rate of 2 inches per hour, and at <br />site 2, an undisturbed sandy loam adjacent to the reclaimed area yielded an <br />infiltration rate of 14 inches per hour. The lower infiltration rate over the <br />spoils was attributed to a mixing df topsoil types, Coalmont and Fluetsch. <br />The initial infiltration rates in the reclaimed areas are expected to be lower <br />than the pre-mining conditions. <br />A water quality sample from a spoil well at the Wyoming Fuel mine indicates <br />that the spoil water is shifted from a sodium oicarbonate type to a sodium <br />sulfate type. To date, spoil aquifers have not developed in the Kerr and <br />Bourg Mines. <br />