Hydrogeologic conditions and projections related to mining near Colstrip, southeastern Montana. Bulletin 102

Technical Report · Wed Jun 01 04:00:00 EDT 1977

OSTI ID:5221682

Van Voast, W A; Hedges, R B; McDermott, J J

The Rosebud and McKay coal beds are important aquifers and are the objects of strip coal mining near Colstrip. They transmit about 5,000 cu. ft. of ground water per day across areas that will probably be mined. Hydraulic conductivities and storage coefficients for mine spoils are similar to those of confined coalbed aquifers. Implications are that spoils do not act as barriers to ground-water flow and that rubble zones along the mine floors contain water under pressure greater than atmospheric. Groundwater quality near Colstrip is diverse. Dissolved-solids concentrations range between about 400 and 6,000 mg/l and are generally highest in waters from the oldest mine spoils. Sulfate is the predominant anion; no specific cation is predominant. Dissolved lead is detectable in most waters in the area; concentrations appear somewhat higher in waters associated with mine spoils than in other waters. Mine-cut effluents are chemical mixtures of ground waters normally discharging along outcrops and subcrops; they have not caused degradation of water quality. Water-level measurements since 1974 have detected no mining-related changes around the Rosebud mine; within 1/sup 1///sub 2/ miles west of the Big Sky mine, declines have been 1 foot or more. Ultimately, active mine cuts may physically destroy five reservoirs, four springs, and twenty-six wells; in addition reliabilities of four reservoirs, three springs, and nine wells may be reduced. Where ground-water supplies are lost, new ones will be obtainable from wells completed in deeper aquifers. After mining, ground-water-flow patterns will reestablish in the reclaimed areas and will not differ greatly from present patterns. Ground waters will be chemically diverse; principal constituents will probably be magnesium and sulfate, and dissolved lead concentrations may be generally higher than before.

• Research Organization: Montana Bureau of Mines and Geology, Butte (USA); Montana Coll. of Mineral Science and Technology, Butte (USA)
• OSTI ID: 5221682
• Report Number(s): NP-22832
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
012000* -- Coal
Lignite
& Peat-- Mining
520100 -- Environment
Aquatic-- Basic Studies-- (-1989)
54 ENVIRONMENTAL SCIENCES
ALKALINE EARTH METALS
AQUIFERS
COAL MINING
ELEMENTS
ENVIRONMENTAL EFFECTS
FORECASTING
GEOLOGY
GROUND WATER
HYDROGEN COMPOUNDS
HYDROLOGY
LEAD
MAGNESIUM
METALS
MINING
MONTANA
NORTH AMERICA
OXYGEN COMPOUNDS
SULFATES
SULFUR COMPOUNDS
SURFACE MINING
TRACE AMOUNTS
USA
WATER
WATER QUALITY