GROUND-WATER MONITORING IN THE POWDER RIVER BASIN, SOUTHEASTERN MONTANA
The Montana CBM ground-water monitoring program is based on scientific concepts developed over more than 30 years of coal-mine hydrogeology research. The program includes inventories of ground-water resources and regular monitoring at dedicated wells and selected springs. The program is now providing baseline potentiometric and water-quality data, and will continue to be active through the duration of CBM production and post-production ground-water recovery.
In southeastern Montana 158 wells and 29 springs are currently included in the program, and they monitor coal beds, adjacent sandstone units, or alluvium. After 4 years of CBM production, ground-water levels within the producing area have been lowered by as much as 150 feet and by about 20 feet, 1 to 2 miles outside the producing area. CBM production water is dominated by sodium and bicarbonate ions, with sodium adsorption ratios greater than 30 and total dissolved-solids concentrations typically between 1,000 and 2,000 mg/L.
Coordinating the needs of several agencies through a single agency for data collection and reporting improves the economic efficiency and reliability of the program. All data collected as part of this program are made immediately available to the public on the Internet at http://mbmggwic.mtech.edu/. Data and reports are used by industry, landowners, regulators and researchers. Funding for this program is provided by the U. S. Bureau of Land Management, U. S. Forest Service, U. S. Environmental Protection Agency, local Conservation Districts and the State of Montana.