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Surface Water Baseline Quality <br /> Surface water quality consists of water in the Hay Gulch Ditch, storm water runoff water,and water in the <br /> Mormon Reservoir. Irrigation water in the Hay Gulch Ditch is monitored as is water quality in the Mormon <br /> Reservoir.To date,there are no data on water quality in storm water runoff.The Hay Gulch Ditch derives <br /> its irrigation water from the La Plata River and the ditch water picks up some salinity from the Hay Gulch <br /> Valley floor(OSMRE 2017).The pH of Hay Gulch Ditch water is around 8.2 standard units(su)and the total <br /> dissolved solids (TDS) ranges from 180 to 320 milligrams per liter (mg/L). Stiff diagrams prepared by <br /> OSMRE (2017) indicate that the water is mainly calcium bicarbonate water. Water in the Mormon <br /> Reservoir, however, is mostly calcium/magnesium sulfate water with a pH around 7.8 su and a TDS <br /> between 1,000 and 1,500 mg/L. The elevated TDS is due to evaporative concentration and contributions <br /> from alluvial groundwater (OSMRE 2017). Complete water quality analyses can be found in RHS(2016b). <br /> 2.3.1.4 Groundwater Resources <br /> Groundwater in the Project Area and the CIAA is found in the alluvium of Hay Gulch and other drainages <br /> and in bedrock in the Cliff House Sandstone, Menefee Formation, and the Point Lookout Sandstone <br /> members of the late Cretaceous Mesaverde Group. <br /> Groundwater Regulatory Requirements <br /> Groundwater use by mining activities is regulated by 30 CFR 816.4(h),which states that if the water supply <br /> of an owner of interest for domestic, agricultural, industrial, or other permitted use is adversely impacted <br /> by contamination, reduction in water supply, or interruption of water supply from surface mining <br /> activities, the impacted water resource shall be replaced by the mining activity at fault. GCCE monitors <br /> groundwater quality and quantity from numerous bedrock and alluvial monitoring wells. The location of <br /> the monitoring wells is shown in Figure 2.3-3 and the well data are presented in Table 2.3-1. <br /> Alluvial Groundwater <br /> Alluvial groundwater is present in some of the unconsolidated alluvial sediments that fill topographic lows <br /> in ephemeral stream systems. These alluvial sediments are composed of fine sand eroded from the <br /> Mesaverde formations. Alluvium in the upper reaches of drainages is typically not saturated, while <br /> alluvium in the lower reaches of drainages can be saturated in the spring and have a water level greater <br /> than 6 ft bgs during the summer months. Hay Gulch has groundwater that is sufficient in quantity for <br /> agricultural and stock watering use. Other drainages in the CIAA, such as East and West Alkali Gulch, <br /> usually have insufficient groundwater for agricultural use. The alluvial aquifers are not known to have <br /> substantial clay covers and are therefore characterized as unconfined aquifers (RHS 2016a). <br /> Dunn Ranch Area LBA and Mining Plan Modification 56 <br /> Technical Resources Report <br />