The intersection of Penn Avenue and Stanwix Street, Downtown, will be closed for 12 hours tomorrow by the Port Authority.

Traffic already is restricted in that area around the authority's tunnel project from Downtown, under the Allegheny River to the North Shore.

The intersection will be closed from 5 a.m. to 5 p.m. while workers place concrete on the floor of the boring machine's receiving pit.

Regular traffic will be diverted to Sixth Street to get to Liberty Avenue.

The closure will affect only one outbound bus route, the 31D-Bridgeville.

That route will turn left off Penn Avenue onto Fifth Avenue and directly to Liberty where it will resume its normal route, the Port Authority said.