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w w W Salinity increases resulting from coal mining include: ..... -leaching of coal spoil materials, -discharge of saline ground waters, and -increased sediment yields resulting from surface-disturbing activities. Spoil materials have higher permeabilities than similar undisturbed areas, allowing most of the precipitation falling onto spoils to inftltrate. The water percolates through the unconfmed spoils encountering more mineral surfaces. The water moves vertically until it encounters undisturbed bedrock. The bedrock will be less permeable than the spoil material, creating a spoil pile aquifer. This increase in contact surfaces and residence time allows greater opportunity for dissolution of these soluble minerals. At some time in the future, the saturated spoils will begin discharging to the surface water systems. Studies conducted on post-mining spoils in northwestern Colorado indicate that dissolved solids concentration of waters flowing from these spoils range from 3,000 to 3,900 mg/I. Salinity concentrations flowing from spoils vary depending on water residence time and the chemical and physical properties of the spoils. Increased dissolved solids concentrations resulting from leaching of spoil materials can last for thousands of years. The time required to reduce the dissolved solid concentrations to pre- mining levels is dependent on spoil pile size, porosity of the spoils, and the annual precipitation of the area. The Bureau of Land Management along with the U.S. Geological Survey's (USGS) Water Resource Division, and Office of Surface Mining, are currently studying the rates of movement of recharge through coal spoils, increases in concentrations of dissolved constituents, regional ground water movement, and crop tolerance. This is the most current stage of the BLM's long-standing efforts with the USGS from 1975 to evaluate the problems related to coal drainage. The dewatering of coal mines may increase salinity concentrations in the Colorado River. The disposal of the water is necessary if the volume exceeds the needs of the mine itself. The discharge of excess water to receiving waters requires a National Pollutant Discharge Elimination System (NPDES) Permit as required by the Clean Water Act. Before a coal lease is issued, an environmental analysis is conducted to assess the impacts associated with the leasing action. Increased salt loading to the Colorado River is analyzed and mitigating measures recommended. When the lease is issued, the company completes a detailed mining plan. The Office of Surface Mining is required to complete another environmental analysis prior to issuance of the permit to mine. At the mine-permit analysis stage, specific salt-load analyses are conducted again with mitigation measures incorporated. Saline waters are also a by-product of oil and gas production. It is not uncommon to produce much more saline waters than oiL The salinity of these production waters varies greatly from location to location and is dependent on the producing formation. Common disposal techniques include injection and disposal in lined and unlined pits. The approval authority for produced water disposal varies from State to State, with the exception of underground injection which is administered by the State or EP A. The BLM's requirements for production water disposal methods are outlined in Notice to Lessees and Operators of Federal and Indian Oil and Gas Leases No. 2B (NTI...-2B). The disposal of production waters in lined pits relies on evaporation as a water disposal method. For this method, the operator must periodically dispose of precipitated solids and analyze water, type of liner, and leak detection system. 14