Laserfiche WebLink
-3U- <br /> The Coal 3asin -line loadout obtains domestic, irrigation, and industrial <br /> water from three ground water wells completed in the Roaring Fork <br /> alluvium. ,Jells No. 1 and 2 have a combined withdrawal rate of 3 <br /> acre-feet/year. well No. 3 is used as a backup well . <br /> In general , the alluvial deposits along Fournile Creek, Thompson Creek, <br /> and Coal Creek are restricted to thin, discontinuous, narrow bands along <br /> the stream channels. Wider bodies of alluvia are located at the <br /> confluences of two or more streams. Alluvial bodies are broken at water <br /> gaps (e.g. , narrow passes through resistant units) . At these points, the <br /> upstream alluvial 'body discharges to the surface stream and the <br /> downstream alluvial body is recharged by the stream. Therefore, the <br /> alluvia of these. streams do not represent a continuous band tributary <br /> from the mine sites to the Crystal River and the Roaring Fork River <br /> alluvia. As a result of this phenomenon any impacts to the alluvia <br /> ground water quality or quantity at the mine sites will directly impact <br /> the quality of quantity in the associated stream. The alluvial ground <br /> water flows are the most significant sources of base flows in the streams <br /> during low flow periods. <br /> The alluvium of North Thompson Creek ranges in thickness from zero feet <br /> at the western end of the mine site to 33 feet at the lower end of the <br /> refuse pile. The alluvium below the refuse pile has a higher clay and <br /> silt content than other alluvium along North Thompson Creek. The <br /> estimated transmissivity from slug tests in this area is 31 gpd/ft. The <br /> water quality below the refuse pile and downgradient of the two wash <br /> plant settling ponds has high total dissolved solids (3498 to 3982 mg/1 ) <br /> and sulfate concentrations (1900 to 2700 mg/l ) . The water type is <br /> calcium-magnesium sulfate. This water quality may be the result of both <br /> the salinity of the underlying Mancos shale and the effects of the mining <br /> operations at the North Thompson Creek Mines. <br /> The alluvium of Coal Creek and its tributaries consists of sands and <br /> gravels derived from the Mesaverde Group, Mancos shale, and reworked <br /> glacial and terrace deposits. This alluvium is discontinuous, varies <br /> between 0 and 75 feet and is highly permeable. The Coal Creek alluvium <br /> is isolated into separate narrow alluvial bodies by water gaps formed by <br /> the resistant sandstone strata. The alluvial ground water is <br /> predominantly a calcium, sodium, megnesium bicaroonate type. The total <br /> dissolved solids concentration is about 350 mg/l . Alluvial ground water <br /> is utilized by Coal creek line for domestic and industrial uses. The <br /> alluvial ground water discharges to Dutch, Coal, Bear and Porcupine <br /> Creeks. This yround water discharge represents base flow in the creeks <br /> during low flow periods. The alluvium is recharged directly from the <br /> streams during snowmelt and during precipitation events. <br /> The unconsolidated landslide deposits support spring and seep =icws in <br /> ;he Coal Basin Drainage. During spring snornnelt, these aeposits <br /> recharge. The ground .water ,ni,rates to .ne toe of the slides and <br /> Jiscnarces as intermittent springs ,and seeps. <br />