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thickness and hydraulic conductivity of the alluvial deposits. Recharge to alluvial aquifers <br />occurs as infiltration from snowmelt and precipitation and as seepage losses from streams. <br />Baseline groundwater quality studies for the Yoast Mine included the alluvial aquifers, the <br />Middle Coal Group, and the Trout Creek Sandstone. The following table summarizes baseline <br />data for pH, SOa, and total dissolved solids (TDS) for the units mentioned above. <br />Aquifer <br />pH <br />SOa (mgJb, <br />TDS (mgA) <br />Annand Draw Alluvium <br />7.5 <br />632(avg.) <br />816-1802 <br />Grassy Creek Alluvium <br />7.02-7.42 <br />167-2517 <br />546-4030 <br />Sage Creek Alluvium <br />6.7-8.3 <br /><539 <br />344-1146 <br />Lennox Coal <br />6.7-7.0 <br />303-480 <br />920-1200 <br />Lennox Overburden <br />6.8-6.9 <br />1790-4157 <br />2030-6432 <br />Wadge Overburden <br />6.5-8.8 <br />99-1737 <br />549-3052 <br />Wadge Coal <br />>12 <br /><500 <br />234-1232 <br />Wadge Underburden <br />6.9-7.0 <br />14-696 <br />996-1550 <br />Wolf Creek Coal <br />6.9-8.5 <br />346-416 <br />904-988 <br />Trout Creek Sandstone <br />7.2-8.25 <br />—412 <br />—871 <br />Climate <br />The average annual precipitation of the town of Hayden, Colorado, 8.5 miles northwest of the <br />mine site, is approximately 15.9 inches. Precipitation for Hayden is relatively uniform <br />throughout the year. The mean annual temperature is 42°F, with an average maximum and <br />minimum temperature of 66°F and 17°F, respectively. The predominant wind direction at the <br />Seneca II -W Mine, located west of the Yoast Mine, is from the east-southeast. This direction is <br />in conformance with the topography of the site, and therefore may not be indicative of expected <br />wind directions at the Yoast Mine. The average wind speed at the Seneca II -W Mine is 3.5 <br />knots, with an average maximum of 15.4 knots, and an average minimum of .17 knots. <br />Vegetation <br />Five major vegetation community types occur within the Yoast permit area. These major <br />vegetation community types are: Mountain Brush, Sagebrush, Aspen, Steep Mountain Brush, <br />and Western Wheatgrass/Alkali Sagebrush. Additional community types occur within the permit <br />area, but are considerably smaller acreages. These additional vegetation types include: Upland <br />and sub -irrigated improved pasture, mesic drainage, lands in the Conservation Reserve Program, <br />cropland, Alkali Sagebrush/Greasewood, and Alkali Meadow. <br />Shrub stands in the pre -mine landscape are dense and reduce the utility of the area for livestock <br />grazing. Pre -mine densities determined from baseline sampling data are: 12,562 stems per acre <br />in the Mountain Brush community, 7,039 stems per acre in the Aspen community, and 6,087 <br />stems per acre in the Sagebrush community. All vegetation types within the permit are <br />characterized by cool season species. <br />