Laserfiche WebLink
distance beyond within the Upper Grassy Creek Alluvium. This diminution <br /> of TDS will result from low hydraulic conductivities in the Grassy Creek <br /> Alluvium, additional downgradient chemical changes, and dilution and <br /> mixing from shallow bedrock units which discharge to the alluvium. <br /> Seneca Coal Company predicts that the maximum TDS increase in the <br /> Annand Draw Alluvium will be 58% immediately below the resaturated <br /> spoil, attenuating to less than 5% near the confluence of Lower Grassy Creek <br /> and Scotchman's Gulch. The predicted TDS increases in the Grassy Creek <br /> and Annand Draw Alluvium will not preclude use of the alluvial groundwater <br /> for livestock watering, although the low well yields in these areas may <br /> already render these aquifers useless for these purposes. <br /> In the Sage Creek Alluvium, the predicted TDS increase immediately below <br /> the resaturated spoil is 99%, but attenuates to 0.1% within 1000 feet. The <br /> high hydraulic conductivities of greater than l ft/day measured in the Sage <br /> Creek alluvium, in combination with the large area of alluvial material, <br /> provides for a relatively high volume of flux in the Sage Creek Alluvium. <br /> Contributions from tributary alluvium and shallow bedrock units will provide <br /> dilution of the spoil discharge as it mixes with much larger volumes of <br /> groundwater in the Sage Creek Alluvium. The point at which the TDS <br /> increase in the Sage Creek Alluvium is predicted to attenuate to 0.1% is just <br /> above a potentially subirrigated field. Therefore, the impacts to the field are <br /> predicted to be negligible. The minimal increase in downgradient TDS levels <br /> will also not affect the suitability of the groundwater for livestock watering <br /> uses. <br /> Hydrologic monitoring will be implemented by SCC in order to verify the <br /> predicted impacts. The proposed hydrologic monitoring program is outlined <br /> in Tab 15 of the PAP. <br /> Surface Water <br /> The probable hydrologic consequences of coal mining at the Yoast mine in <br /> regard to surface water include contributions of sediment to streams from <br /> storm runoff, and impacts to stream water quantity and quality during and <br /> after mining. Potentially affected streams and drainages include Annand <br /> Draw, Grassy Creek, and Sage Creek. The most significant impact of mining <br /> on surface water will be the effect of spoil spring discharges from the <br /> reclaimed mine on surface water quality. Seneca Coal Company's predictions <br /> of the magnitude of these impacts is discussed below. <br /> Yomt Kline 26 October 19, 1999 <br />