The demolition of the historic Sixth Street bridge that connects Boyle Heights with downtown Los Angeles is back on.

Originally set for earlier this month, the city will begin demolishing the 3,500-foot concrete structure, officially known as the Sixth Street Viaduct, on Wednesday.

The roadway will be closed from Mateo Street on the west and Boyle Avenue on the east, announced the Los Angeles Bureau of Engineering Thursday so crews can begin tearing down the 84-year-old structure. The bridge suffers from a chemical deterioration of the concrete that makes it vulnerable to collapse during a major earthquake.

Demolition will take nine months. Construction of a new viaduct will be completed in late 2019, said Caltrans.

To make way for the demolition of the bridge which hangs over the 101 Freeway, the freeway will be closed for 40 hours beginning Friday, Feb. 5 at 10 p.m. until Sunday, Feb. 7 at 2 p.m., the city and Caltrans announced.

The 2 1/2-mile section of the 101 in downtown L.A. will be closed to all traffic at the 10/101 juncture just east of downtown to the 5/10/101 interchange. Also, motorists traveling west on the 60 Freeway from the San Gabriel Valley will not be able to access the 101 Freeway.

“We are encouraging drivers to plan ahead, expect delays and to follow detour signs to alternate freeways,” said Carrie Bowen, director of Caltrans’ District 7, which includes Los Angeles County.

A new bridge will be built complete with arches, a bikeway and a walkway. The project costs $445 million.