Pastor Calvin Cash is turning water from an abandoned underground coal mine into big utility cost savings at the John Wesley A.M.E. Zion Church in the Hill District.

And he wants to multiply the church's good fortune by using its new energy-efficient geothermal heating and cooling system to spur residential and commercial development of now-vacant land adjacent to the church along Herron Avenue.

The geothermal system, using the 55-degree mine water to transfer heat into and out of the church, has been in daily operation for three weeks. Although the church has yet to receive an electric bill, it projects a 75 percent savings on heating and 50 percent savings on cooling costs.

Mr. Cash said the 2,400-square-foot church is using only about 25 percent of the geothermal system's capacity.

"We haven't sold off our excess capacity," he said. "Creating a 'green corridor' along Herron Avenue is our overall vision, and the lowered heating and cooling costs would be an attractive feature that a developer could incorporate into a commercial, residential or mixed-use building."

The land is owned by the Urban Redevelopment Authority. A developer willing to build on the land adjacent to the church would be able to tie into the geothermal system, which was paid for with an $80,000 grant to the Herron Avenue Corridor Coalition from the Pennsylvania Energy Harvest program and $12,000 from the Western Pennsylvania Watershed Program.

The system is tapping into mine water that until 2004 regularly flooded the basement of the church and left an unsightly iron orange stain on its walls.

In the summer, the cool water is pumped through the building to cool the air. In the winter the water is heated and pumped through the building, but requires much less energy to heat because it is already 55 degrees.

The Hill District was one of the most heavily mined areas of Pittsburgh in the early 1800s because coal seams either outcropped or were close to the surface. Mining ended there in the late 1800s but mine drainage out of the abandoned mines and subsidence problems still occur.

"I never thought when I became a pastor that I'd be researching geothermal heating and cooling systems, but this project made me do that," Mr. Cash said. "There's nothing in my biography that indicates an engineer. I'm an engineer for the Word."