Pittsburgh's Urban Redevelopment Authority gave the go-ahead Thursday for construction of a major linchpin that will connect the network of hiking and biking trails that run along the banks of the Allegheny, Monongahela and Ohio rivers.

The authority unanimously approved a series of contracts for the construction of a 14-foot-wide pedestrian and biking trail along a portion of the nearly 1,100-foot Hot Metal Bridge, which runs from the South Side Works over the Monongahela River to Second Avenue in Oakland.

An entrance to the South Side Trail -- which begins near Station Square and runs upriver about 6 miles to the Glenwood Bridge -- is located along the river at South Side Works.

A new 136-foot pedestrian bridge will be built over Second Avenue to connect with the Eliza Furnace Trail, which is about 3 miles long and connects Oakland to Downtown. From Downtown, bikers or hikers can cross over one of several bridges and pick up the North Shore Trail, which runs along the Ohio River near Heinz Field and up the Allegheny River to Washington's Landing.

The Hot Metal Bridge work and the new Second Avenue connector bridge will cost about $6.5 million, said John Coyne, the URA's director of engineering and construction. The bulk of the project is being paid for with federal dollars, although additional money will come from the city, the URA and the Allegheny Trail Alliance.

Work is expected to begin this fall, with completion slated for fall 2006, Coyne said.

URA Chairman Tom Cox called the linking of the various trails around the city "a milestone."

"In 12 years, we've been able to develop a trail system that has taken Pittsburgh from kind of a shameful position in American cities to one that has gotten a lot of national recognition," Cox said.

The contracts, all approved unanimously by the URA board, gives the agency the go-ahead to advertise, bid and award contracts for construction. Trumbull Corp., of West Mifflin, received a $490,000 contract to serve as construction manager for the project. Parsons Brinckerhoff Quade and Douglas Inc., of Norfolk, Va., was awarded a $225,000 contract to provide engineering services.