Many closed coal mines are proving valuable once again. When the mines were open, water was always a concern and required continuous pumping to keep it out of miners' way. Now, however, that water in those mines is providing a home for a new industry—raising coldwater fish.

Clean mountain water continually seeps into the mines, and the low sulfur content makes the water highly desirable. In addition, the water is groundwater and therefore has a constant temperature. That is an advantage over farms that use surface water, according to Matt Monroe, coordinator of High Appalachian, a government-run trout farm deep in West Virginia's coalfields that processes about 200,000 pounds of fish a year for grocery stores, restaurants and hotels.

One of the fastest growing sectors in U.S. agriculture, fish farming became a $1 billion industry in 1998. Demand for seafood has risen, but overfishing and increased regulatory pressures led to a decline in the harvest of wild fish. Thanks to the coal mines, West Virginia alone has enough water resources to increase annual production from 400,000 pounds of fish to 10 million pounds, says Joe Hankins, director of the National Conservation Fund's Freshwater Institute.