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1. Surface Water Effects <br />An evaluation of the cumulative effects of mining on surface water is limited <br />because the receiving water, Hay Gulch, is an alluvial body and not a flowing <br />stream. Each of the three mines contained within the surface water cumulative <br />impact area are located within ephemeral drainages immediately adjacent to the <br />valley of Hay Gulch. Surface water discharges occur as a result of periodic <br />discharges of effluent from sediment ponds during storm events. No baseflow, <br />either as streamflow or alluvial ground water, is evident at any of the three <br />mines. As such, effects on surface water are limited to the direct effects of <br />mining on surface water contained within the respective mine permit boundaries. <br />Each mine has provided a statement of probable hydrologic consequences as a <br />part of their individual permit applications. All three mines have identified <br />increased erosion rates from disturbed areas as the primary effect of mining. <br />A limited potential exists for increases in total dissolved solids <br />concentrations (TDS) in mine effluent. The increases in TDS may result from <br />dewatering of perched aquifers or subsidence related ground water discharge to <br />the surface water system or from contact of surface water with coal fines on <br />the mine benches at these three mines. Any increases in TDS are expected to <br />be small since the dilution of surface water discharges with elevated TDS in <br />the volume of alluvial ground water is sufficient to limit the impact on the <br />receiving water. A small amount of acid drainage from the La Plata No. 1 Mine <br />has been documented to occur (4 to 5 gallons per minute), however a treatment <br />system will be installed to neutralize this water. Effects of mining on <br />surface water are controlled at each of the three sites through the use of <br />sediment ponds and treatment systems. Cumulative impacts are limited to the <br />effects on ground water as discussed in the following section. <br />2. Ground Water Effects <br />As discussed in Sections V - Ground Water Hydrology and above in this section <br />of this document, the Menefee Formation in the vicinity of Hay Gulch is <br />essentially dry. Due to lithologic and topographic variables, limited perched <br />aquifers will exist within the formation, Mining activities will dewater <br />those perched aquifers which overlie the operations. As these aquifers are <br />not contiguous and are not put to any use in this area, no impact to the <br />hydrologic system will be realized. Water from disrupted perched systems may <br />discharge from up-dip mining entries (La Plata No. 1 Mine). Water flowing <br />into down-dip mining operations (King Coal and Blue Flame) will tend to flow <br />away from the mine entries, perhaps recharging the coal face when mining has <br />ceased. <br />Due to the hydrologic and geologic characteristics of the Menefee Formation, <br />as well as local topographic controls, no significant hydrologic impacts to <br />this system are anticipated. <br />-15- <br />