2010-12-14_REVISION - C1994082 - Laserfiche WebLink

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predominated upstream from the permit area. TDS ranged from 680 to 853 mg/1 at high and low flows, respectively. Permit Area Intermittent flows from the northern side of the permit area drain through Annand Draw into Scotchmans Gulch, and then into Grassy Creek. Spring flows in Annand Draw are predominately from the melting of snowpack. Late spring to early summer flows are a combination of bank storage, runoff from precipitation events over saturated or frozen ground, or perched spring flow recharged by snowmelt. The remainder of the year, the channel exhibits ephemeral flow characteristics. The mean flow rate in the spring is .056 cfs, and .02 cfs in the summer. Within the permit area, there are five primary drainages, four of which are ephemeral. The drainage channels have been identified as Annand Draw, 011 Draw, Y1 Draw, Y2 Draw, and Y3 Draw. Annand Draw is intermittent. The drainage patterns exhibited in these draws are a combination of parallel and dendritic. The drainage densities are moderate (7.26 to 10.38 mi/mi), channel sinuosities are low (1.01 to 1.07 mi/mi), and channel gradients are moderate to steep (.039 to .218 ft/ft). Ground Water Aquifers of particular interest in the permit area include the coals and interbedded units of the Williams Fork Formation Middle Coal Group as well as the overlying Twentymile Sandstone and the underlying Trout Creek Sandstone. Recharge to the bedrock aquifers occurs as infiltration at the outcrops, which are parallel to the axis of the Fish Creek Anticline. Discharge is through bedrock springs, which are tributary to Sage Creek and one in the upper reach of Annand Draw. Bedrock groundwater is confined except in outcrop areas. Baseline studies showed that the Lennox Overburden and Coal units are artesian flowing aquifers. The Wadge Overburden occurs under confined and unconfined conditions. The unconfined conditions are encountered near the outcrops. The saturated aquifer thickness of these units ranges between four and 200 feet. The Wadge Coal aquifers appear to be largely confined, whereas the Wadge Underburden aquifer occurs under both confined and unconfined conditions. The Wolf Creek Coal occurs under confined conditions, however the Wolf Creek Underburden is both unsaturated and unconfined. Movement- of groundwater in bedrock aquifers is controlled by structural folding and faulting and stratigraphy. Confined conditions occur at synclinal axes, and unconfined conditions occur near the outcrops. No significant faulting is known to occur within the permit area. Two recharge boundaries are known to exist in the permit area. An erosional face along the northerly-plunging axis of the Fish Creek anticline provides a localized recharge boundary for the Wadge Coal and Wadge Overburden. Additionally, the Wolf Creek Coal outcrop, parallel to the axis of the Fish Creek Anticline, is a recharge boundary for the Wolf Creek Coal. Yoast Mine 12 December 15, 2010