Allegheny County will begin a two-year project Saturday to upgrade the Armstrong Tunnel and change the traffic pattern inside the connection between Second Avenue and Forbes Avenue in Uptown.

The $13.1 million project by Mosites Construction Co. will begin with the closure of the inbound tunnel at 6 a.m. Saturday. Additionally, the right, inbound lane of Second Avenue will close at the intersection with the tunnel.

The county said the work is needed to extend the life of the 97-year-old tunnel and make sure it is safe for the just over 11,000 motorists who use it every day.

The Federal Highway Administration is paying 80% of the cost, the county 20%.

The first part of the project will have different detours for cars and trucks. Cars should follow Second Avenue inbound to Ross Street to Forbes Avenue while trucks should follow Second Avenue to B Street, First Avenue, Grant Street, Boulevard of the Allies, Commonwealth Place, Liberty Avenue, Fifth Avenue and Sixth Avenue to Forbes.

Recent inspections showed the 1,298-foot tunnel needs concrete repairs, removal of the ceramic tile liner and new lighting fixtures, as well as improvements to bring its safety system up to current standards. Crews will install new fireproof wall panels, clean masonry at the entrances and exits of the tunnel, and install a closed-circuit television system, pavement, curbs, a sidewalk, signs and pavement markings.

Besides improving the physical elements of the tunnel, the project is designed to slow traffic and increase driving safety.

Instead of two 10-foot lanes and no shoulders, the rehabilitated tunnel will have one 12-foot lane in each direction. The inbound tunnel will have 4-foot shoulders up to the exit, where there will be two right-turn-only lanes, while the outbound tunnel will have 2- to 3-foot shoulders until the exit, where there will be a left-turn lane and a straight/right-turn lane.

The sidewalk on the outbound side will be expanded from 3 feet, 9 inches to 6 feet, 3 inches.

Named for former county commissioner and Pittsburgh Mayor Joseph Armstrong, the tunnel opened in 1927 and is listed on the National Register of Historic Places.

Ed covers transportation at the Pittsburgh Post-Gazette, but he's currently on strike. Email him at eblazina@unionprogress.com.

Ed Blazina

Ed covers transportation at the Pittsburgh Post-Gazette, but he's currently on strike. Email him at eblazina@unionprogress.com.