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Probable Hydrologic Consequences and Cumulative Impact Assessment - Ground Water Effects of Mining on the Hydrologic Balance - Ground water A. General Background - ,Nine Area The Kerr Coal Mine is stripping the Sudduth coal seam on the western limb of the Johnny Moore Syncline. The Johnny Moore Syncline is a tight asymetric plunging sycline. The western limb is the more steeply dipping limb, and the syncline plugs to the southeast. Faults cut across the syncline and streams have become insized in these fault zones. The Sudduth coal seam in both the east and west limb of the Johnny Pfoore Syncline subcrops under the stream valleys, (see Map 15a). Kerr Coal Company has identified three aquifers; alluviums of the intermittent streams, Upland Terrace Deposits and Sudduth coal seam. The alluviums of the intermittent streams are located in narrow bands along the stream channels. These deposits consist of lenticular sands, gravels and silty clays (page 779-29aa and Map 40a). Water is stored and transmitted within the sand and gravel leases. There exist no mines in the alluvium of the streams in the mine plan and adjacent areas, however the alluvium provides subirrigation to these valleys. The Upland Terrace Deposits consist of river alluvium which was deposited when the Canadian River was at an elevation of 8,200 feet. These deposits have since become eroded as the Canadian River and its tributaries have become incised. These deposits have svfficientpermeability to store and transmit water. Only one spring is associated with the Upland Terrace Deposts, and is located in Section 22, T9N, R78W. This spring discharges from the contact between the Upland Terrace Deposits and the underlying shale unit. This spring receives water which infiltrates these deposits and flows down gradient along the bedrock contact. The water from this spring is used for stock evatering. The Sudduth coal seam is the only rock unit of sufficient permeability and areal extent in the mine plan and adjacent areas to be considered a regional aquifer. These statements are adequately supported by exploration drill hole logs contained in Exhibit 22a and by the pumping test results contained on Table 9, Exhibit 54, pages 779-30aa and bb, and "Hydrology of the McCallum Study Area", by Warren Hoffstra, U.S.G.S. Open File Report. The pumping tests and the overburden run by Warren Hoffman of the U.S.G.S. yielded permeability of 0.37 gpd/ft2 in unfavlted overburden and 7.5 gpd/ft2 in faulted overburden. These values indicate that the overburden is a confining unit aquiclude and not an aquifer. The Upper Coalmont formation which is Located at the center of the Johrnu Moore Syncline, however, contains very localized sandstone aquifers. These sandstone aquifers are isolated channel sandstones with Zimited areal extent. One of these channel sands, which is about 26 feet thick, provides a water supply for the Kerr Coal mine. The Kerr Coal Mines's well is located in Section 35, T9N, R78W, and is permitted under Colorado water we21 permit No. 020253-F. This well is the only r^ermitted well Located in the Johnnu ,7oore Syncline. Kerr Coal Company conducted a pumping test on the underburden, Upper Pierre Shale. They calculated a permeability of 0.15 gpd/ft2 and had no drawdown in a Sudduth coal seam well 20 feet away. This indicates that the underburden is not an aquifer and acts as an agviclude to the overlying coal seam aquifer. No wells are Located in the underburden and there are no known seeps or springs from this unit in the adjacent area. -10-