Laserfiche WebLink
-29- <br /> Unconsolidated colluvial and landslide deposits exist along the slopes of <br /> the ridges formed by the more resistant sandstones. The east-facing dip <br /> slopes along the Grand Hogback are naturally unstable slopes. Numerous <br /> landslides have developed on the unstable slopes, which has led to the <br /> characteristic hummocky topography. <br /> Ground Water <br /> The general area around the three mines contain four types of aquifers; <br /> alluvial , continuous bedrock, laminar to lenticular discontinuous <br /> bedrock, and fracture aquifers. The regional movement of ground water is <br /> controlled by the geologic structures along the Grand Hogback ( i .e. , the <br /> folds and faults.) . Local ground water movement is controlled by the <br /> vertical and lateral extent of the aquifer, and also by the type and <br /> magnitude of localized secondary porosity related to fault, fracture and <br /> joint systems. <br /> The overall regional ground water movement in the general area of the <br /> Coal Basin Mines, North Thompson Creek Mines and the Sunlight nine would <br /> be towards the axis of the Piceance Basin, were it not for the folds and <br /> faults which occur along the Grand Hogback. There is a high displacement <br /> fault north of the Coal Basin itines. This fault restricts the migration <br /> of ground water from the Hunter' s Point Syncline adjacent to the Coal <br /> Basin (Mines and the unnamed syncline adjacent to the North Thompson Creek <br /> Mines, thus forming two separate ground water basins along the Grand <br /> Hogback. <br /> Alluvial ground water aquifers exist along the Roaring Fork River and the <br /> tributaries to the Roaring Fork. These alluvial aquifers are the most <br /> significant source of ground water put to beneficial use in the general <br /> area. The alluvial ground water also serves as the primary source of <br /> recharge water to the underlying bedrock aquifer. The alluvium is <br /> rapidly recharged by the stream and serves as a reservoir for surface <br /> water available for the recharge of bedrock aquifers and fracture <br /> aquifers. <br /> The most significant alluvial aquifers in the general area are the <br /> Roaring Fork and Crystal River alluvia. Many water supply wells are <br /> completed in these aquifers. This is due to their high-storage <br /> capacities and rapid recharge from their associated streams. Two water <br /> supply cells are completed in the Roaring Fork alluvium at the ,'North <br /> Thompson Creek Aine loadout. These .,jells are pumped at a combined rate <br /> of 50 gpm in the summer and 15 gpm during the winter. The water is <br /> considered tributary water to the Roaring Fork River, and is under .n <br /> augmentation plan, which permits water uses of dust suppression, 5. 14 <br /> acre-feet; plant washdown, 2.38 acre-feet; sanitation, 0.02 acre-`pet; <br /> and irrigation, 9.0 acre-feet, for 3 total of 13.04 acre-feet per year. <br /> The alluvium at the North Thompson Cree< %line loadout consists of medium <br /> to coarse grained sand and gravels. The aquifer' s transmissivity is <br /> 51 ,200 gpd/ft. and storativity ,vas estimate, to oe 0.3. The water <br /> quality of the Roaring Fork alluvium is similar to the Roaring Fork <br /> giver. Total dissolved solids ("JS) range detNeen 290 and :,00 mg/I ; and <br /> iron =e) caries oet,,jeen 0 and 0.U3 I;g/1 . The pH is neu;tral to s1igntly <br /> alk3iine, ana the '.Pater type is a calcium, magnesium-oicafoonace, sulfate. <br />