Consol Energy Inc. yesterday announced the biggest capital project in company history, a $500 million expansion of the Enlow Fork Mine in southern Washington County that will create 400 mining jobs.

The expansion would tap Pittsburgh coal seam reserves in Washington and Greene counties for as long as 30 years, Peter B. Lilly, Consol's chief operating officer, said at a press conference at Washington County Airport.

"In other words, Consol will be actively hiring for the next decade, providing job opportunities that will help keep a younger generation of Pennsylvanians here at home," Lilly said.

Enlow Fork currently employs 575 and produces 10 million tons of coal annually, putting it neck-and-neck with Consol's Bailey Mine in Greene County for the distinction of top-producing deep mine in America.

The expansion would put 15-year-old Enlow Fork squarely on top. Lilly said the new longwall operation would boost annual production by about 70 percent, or seven million tons, generating an additional $20 million in taxes and an additional $150 million in spin-off business to suppliers each year.

"This project will have a real impact for communities and people living around here," said Dennis Yablonsky, state secretary of community and economic development, who flew to Washington County for the announcement.

Lilly said Upper St. Clair-based Consol, the nation's largest producer of high-energy bituminous coal, spent about a year developing the project and had begun seeking necessary permits.

He said earth moving and construction would begin in 2006, with coal production beginning in late 2010. The plan would involve construction of a portal and processing plant south of Prosperity, a village in Morris Township, Washington County.

Coal also would be mined in South Franklin, Washington County, and Morris and Washington townships, both Greene County, according to a map Consol provided yesterday. Officials said the expansion would tap reserves in roughly a 50-square-mile area.

Consol is seeking no public subsidies for the project. But Lilly said the company would need a stable regulatory environment -- no sweeping changes in pollution-control requirements, for example -- to sell coal to power plants.

Thomas F. Hoffman, Consol's vice president of investor and public relations, said the expansion is driven by increasing demand for electricity and emerging opportunities for Pennsylvania coal. He said federal regulations requiring power plants to install scrubbers have given a boost to Pennsylvania coal, which can be higher in sulfur than that mined elsewhere.

Lilly said Consol's investment would be the largest in southwestern Pennsylvania in many years. It would be an economic boon to largely undeveloped Greene County and a complement to the retail and office development that's dominated Washington County's growth in recent years.

"The scope of this project is really overwhelming," said state Sen. J. Barry Stout, D-Bentleyville.

The new jobs would add $41 million a year to Consol's Pennsylvania payroll, now $197 million annually. Hoffman said the company employs about 1,950 at four mines, its headquarters, a land company and other operations here.

While touting the economic benefits, officials acknowledged the project would bring subsidence and other inconveniences to residents. Lilly said the company this summer would hold a series of community meetings to explain its plans and let residents voice concerns.