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Water Supplies from Underground Coal Mines in Eastern Kentucky

Contact: Dennis Cumbie

This study assesses the development potential of abandoned underground coal mines as municipal water supplies in the Eastern Kentucky Coal Field. Current water systems using deep mines as primary water sources serve communities as large as 1,500 homes. Development potential depends on storage capacity, the rate of recharge, water quality, and proximity to population centers with water-supply needs.

Thus far, detailed analysis has been completed at sites in Letcher, Perry, Clay, and Harlan Counties. High-volume pumping tests are conducted for mines below local drainage level, and natural discharges are monitored for mines above local drainage. Results from detailed studies indicate recharge rates ranging from 120,000 to 700,000 gallons per day. Storage volumes for these mines range from 260 to 480 million gallons. Previous results from Letcher County show that deep-mine water levels (and thus, storage capacity) vary seasonally.

Water found in abandoned underground mines tends to have higher concentrations of sulfate and dissolved metals (typically iron, magnesium, and manganese) than surface waters because of prolonged contact with pyritic rocks associated with coal-bearing strata. Detailed analysis indicates that water quality varies little over time within an individual mine, but can differ substantially between mines, even for mines within the same coal seam. There is also evidence that water from mines within the same coal seam may have mineral concentrations similar in proportion, but dissimilar in magnitude.

Municipal water systems currently using underground mines as primary water supplies have had few problems with water quantity, and use conventional treatment methods. Another benefit is that mine waters are less susceptible to contamination from surface sources such as hydrocarbons, pesticides, industrial solvents, and human pathogens.

This work has been funded by the Kentucky Infrastructure Authority, the Kentucky River Authority, and the Kentucky Geological Survey.