The federal government has authorized the Pennsylvania Turnpike Commission to move forward with the 24-mile, $2 billion northern end of the Mon-Fayette Expressway in Allegheny County.

The Federal Highway Administration's decision ends a dozen years of preliminary planning, public meetings and debate for one of the largest road-building programs under way in the United States.

Another 10 years of work lie ahead.

The clearance will enable turnpike officials to immediately advance the project to final design of the final section north of Route 51 in Jefferson Hills.

The new road will look like a giant Y from the air, with the bottom of the Y connecting to the finished portion of the expressway. The expressway will cross the Monongahela River in Duquesne and then branch off in two directions, with one branch going to Monroeville and the other connecting to the Parkway East, just west of the Squirrel Hill Tunnel.

Turnpike and FHWA officials today will formally announce the milestone in developing the West Virginia-to-Pittsburgh toll road when the Mon-Fayette Expressway/Southern Beltway Executive Committee of about 100 elected, planning and civic officials meets at the Meadowlands Holiday Inn in Washington County.

The Turnpike Commission has already lined up consultants to prepare the final design, breaking the northern end into 13 sections to spread the work among engineering firms. The final design involves the detailed engineering that results in bid specifications, right-of-way boundaries, architectural features, landscaping, lighting and signage.

The final design phase of the massive undertaking is to take up to four years, followed by property acquisition, utility relocation and, finally, construction.

Although it's a 10-year timetable, turnpike officials have previously said segments of the northern end can be fast-tracked and opened to traffic earlier.

The consultants are to be notified next week to begin their work, ending a yearlong lull in activity while various government agencies reviewed the voluminous Mon-Fayette Expressway study documents and addressed issues raised at public meetings.

Two additional contracts involving railroad relocations and designing toll facilities for the northern section are to be advertised soon.

HDR Inc., an international engineering firm with a Pittsburgh office, will oversee the team of consultants as the turnpike's designated design manager.

Thirty-five miles, or about half of the limited-access highway, are finished and open in Fayette and Washington counties and southernmost Allegheny County. They generated $6.3 million in toll revenue in the last year.

West Virginia has finished half of a southern, four-mile section east of Morgantown but none of the road will be opened until the interchange with Interstate 68 is built. Funding has yet to be lined up, so it will is still some years away.

Turnpike chief executive Joe Brimmeier said the Record of Decision for the northern section of the Mon- Fayette Expressway culminates "12 years of work to identify the best route for the Pittsburgh region's long-awaited Parkway South."

But the route that has already survived numerous objections, from Pittsburgh Mayor Tom Murphy to anti-highway groups, and may face more roadblocks in the future.

"We're going to take a close look at the [FHA decision] and decide where we go from here," said Jeanne Clark, director of communications for the environmental group known as PennFuture. "We've raised questions about the [planning and environmental] process all along and felt the Turnpike Commission failed to obey the spirit if not the letter of the law."

Tom Buchele, head of the University of Pittsburgh's Environmental Law Clinic, said it was still too early to determine whether groups with which he has been linked, including the activist Citizens Against Toll Roads, may sue to try to block the project.

The final Environmental Impact Statement includes a summary of the turnpike's conclusion saying that a "Citizens Plan" advanced by PennFuture was not a reasonable alternative to a high-speed, four-lane road. The PennFuture plan incorporated transit improvements and upgrades to existing highways, as well as limited new construction.

Turnpike officials vowed to continue working closely with Allegheny County communities in order to produce a highway compatible with its surroundings.

Five Design Advisory Teams composed of community and local government representatives are to be established to provide input to engineers and finalize issues raised during the environmental process. The teams will be set up for Dravosburg, Turtle Creek, the Braddock-Rankin-Swissvale area, Nine Mile Run including Duck Hollow, and the Glenwood Bridge-to-Bates Street area that includes South Oakland and Hazelwood.

"We will continue our dialogue and be receptive to local input," said Frank Kempf, the turnpike's assistant chief engineer.

The route that the FHWA approved begins where the expressway (Toll 43) ends at Route 51 in Jefferson Hills.

The road heads north through West Mifflin and part of Dravosburg to a large, new Monongahela River bridge connecting Route 837 and Duquesne at the south end to Braddock Avenue and the Tri-Boro Expressway at the north end, in East Pittsburgh and North Versailles.

The alignment then splits into the Y, with a northeastern leg following the Turtle Creek Valley to Business Route 22 and the Parkway East in Monroeville, and with a northwestern leg following the north shore of the Monongahela River through Braddock and Hazelwood, connecting to Pittsburgh on Second Avenue, Bates Street and the Parkway East below Oakland.

Besides providing a new high-speed route to Pittsburgh from traffic-clogged southern points, the project is intended to spur economic redevelopment in old Mon Valley industrial towns.

The turnpike commission said the expressway will alleviate traffic on overburdened routes such as 51, 837, 885 and 148 as well as provide an alternative to the Squirrel Hill Tunnel.