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<br />f. Quan(i(a(ivr lmpac(s of Mining <br />Groundwater <br />Groundwater monitoring information acquired in the last fourteen years at the New Elk and <br />Golden Eagle Mines consists of water level and water quality information from alluvial wells <br />and estimates of mine water inflows and discharges from the two mines. In addition, this report <br />will make use of water level data acquired in the last few months on historic holes at the site and <br />information acquired during drilling for exploration and degas well development. This report <br />will assess the degree of hydraulic communication between the mine and surface and near <br />surface waters in the valley. It will compare the 1980 estimates on the drawdowns of the <br />piezometric surface and the subsequent recovery of the same, and the quantity of inflows with <br />data actually collected at the site. <br />Mapping of mine inflows has been performed annually and the results have been included in the <br />Annual Hydrology Reports. The stream channels in the area have been superimposed on these <br />maps, and inflows have definitively not been correlated with the expression of stream channels <br />in Apache Canyon, along the Purgatoire, in Ciruela Canyon, or in Santistevan and Zamora <br />Canyons. In addition, monitoring of flow within the streams is performed monthly, and trends <br />• outside the annual seasonal variation have not been observed. Nine springs or seeps within one <br />mile of the New Elk and Golden Eagle permit boundaries have been monitored annually in late <br />summer for ten years without showing any trends in their yield (Basin, 1994}. <br />• <br />Basin noted surficial tension subsidence features over the first longwall panel north of the river <br />immediately ahead of mining. A subsequent observation following mining resulted in an <br />elimination of these features. In addition, subsidence monitoring has recorded a decrease in <br />elevation of the surface approximately the thickness of the coal seam down the center of the <br />panel with more limited elevation changes along the edges of the panel. These observations are <br />consistent with other long wall operations. Hydrologically, the presence of surficial subsidence <br />features and differential elevations suggests that fractures are emanating upwards from the coal <br />seam and increasing the permeability of the overlying formation. The Raton Formation is a <br />series of interbedded fluvial deposits consisting of sandstones, siltstones, shales and coals. <br />Water bearing zones are limited and of low yield and are seen predominantly within channel <br />sandstone deposits of limited lateral extent and in conjunction with the coal seams. Subsidence <br />will integrate the water bearing zones by increasing the permeability for a short duration of time. <br />This may result in increased mine inflows as the water bearing zones are de-watering. The fine <br />grained components of the Raton Formation will tend to close many fractures and the <br />groundwater regime within the overburden will become re-established. <br />8 <br />