Stairs from Second Avenue to the Boulevard of the Allies and one lane of Forbes Avenue will close for two months beginning Monday as part of the rehabilitation of the Armstrong Tunnel.

Allegheny County announced the stairs on the Philip Murray Bridge side of the tunnel will close Monday. The right lane of Forbes Avenue that passes in front of the tunnel will close one week later, Oct. 23.

Pedestrians who use the stairs will have a lengthy detour using Second Avenue, Ross Street and Forbes Avenue. Two lanes of traffic will remain open on Forbes, but there could be some congestion in the area, so drivers are urged to use caution.

These closures are part of a $13.1 million project by Mosites Construction Co. to update the tunnel, which is named for former county commissioner and Pittsburgh Mayor Joseph Armstrong and is listed on the National Register of Historic Places. Right now, the inbound side of the 1,298-foot tunnel and one inbound lane of Second Avenue near the tunnel are closed.

The rehabilitation of the 97-year-old tunnel, which began in March and is expected to last two years, is designed to improve safety for motorists, slow traffic and extend the life of the structure. Work will include reducing traffic to one lane in each direction in wider lanes up to the exit, where there will be two lanes.

Additionally, crews will make concrete repairs, remove the ceramic tile liner and bring the safety system up to current standards. The work also will place fireproof wall panels; clean masonry at the entrances and exits; and install a closed-circuit television system, pavement curbs, a sidewalk, signs and pavement markings.

About 11,000 motorists use the tunnel daily.

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.