Aquifers in the New Leipzig coal area consist of sandstone beds in the Fox Hills Sandstone, the Hell Creek Formation, the Cannonball and Ludlow Members of the Fort Union Formation, and the basal part of the Tongue River Member of the Fort Union Formation. Aquifers also occur in sandstone and lignite beds in the upper part of the Tongue River Member and Sentinel Butte Member of the Fort Union Formation. Potential well yields from each of the aquifers are variable, but are less than 100 gallons per minute. Water in the Fox Hills, Hell Creek, Cannonball, and Ludlow is soft and of the sodium bicarbonate type. Water in basal Tongue River aquifer is either soft or very hard and generally is of the sodium bicarbonate type. Water in the upper Tongue River and Sentinel Butte aquifer system is very hard and generally is either of the calcium bicarbonate or sodium bicarbonate type. There is little or no contribution of ground water to Thirty Mile Creek or the Cannonball River from the area of minable coal. Coal mining will expose sulfide minerals to oxidation, and result in an increase in dissolved solids and sulfate in water in the basal Tongue River aquifer. (USGS)
