The Interstate 59/20 bridges in downtown Birmingham will be closed for an estimated 14 months beginning in the fall of 2018, according to the terms of a new contract for the project.

The Alabama Department of Transportation recently awarded the contract for the third and final phase of the bridge replacement project to Johnson Bros. Corp. based out of Roanoke, Texas. The company bid $474.7 million.

Late last year ALDOT rejected all of the bids for phase three, as they were $150 million over projections. The lowest accepted bid came in at $507.9 million from Granite Construction Co.

Initially, ALDOT estimated phase three of the project to cost an approximate $357 million.

The project was rebid this spring.

Three phases of the Interstate 59/20 bridge replacement. Phase two is about a third complete as of mid-May 2017. The third phase is expected to start by mid-June. (ALDOT)

ALDOT East Central Region Engineer DeJarvis Leonard said Johnson Bros. will implement some "innovative construction techniques to expedite" the construction process.

More details on the future construction are expected to be released next month.

According to ALDOT, the elevated portions of Interstate 59/20 through downtown Birmingham's Central Business District have to be replaced for safety reasons. The bridges are in disrepair - at more than 40 years old - and were only designed for 80,000 vehicles a day. Today, double that amount of vehicles travel on the roadway.

Construction work related to the bridge replacement began in September 2015. Much of the work to date has involved the widening of some roads and elevating of some bridges in the interchange of I-59/20 with I-65 -- known as Malfunction Junction.

Leonard said the major work occurring right now is the construction of a bridge from 11th Avenue over I-59/20 that will connect to I-65 South.

The 31st Street North Bridge, which has been closed for several months for reconstruction, is expected to reopen in about a month, he said.

Earlier this year, ALDOT Director John Cooper said ALDOT will work with the contractor to minimize the closure of the I-59/20 bridges.

"There will be days you can't go through downtown," he said, "but there will never be a day that you can't get to downtown."

When the I-59/20 bridges are closed, Leonard said through traffic will have to use I-459 to get around the city. Traffic will also be able to use I-65 through the city.

Phase three of the project, which will start in the next three weeks includes: the replacement of the I-59/20 bridges, approaches (where the roads meet on the edges) on I-59/20 from the I-65 interchange to north of the 31st Street North interchange. It also includes modifications to the Red Mountain Expressway; drainage and streetscape improvements on 9th Avenue North from the intersection of 15th Street North to the intersection of 23rd Street North and cross streets - 15th Street North through 25th Street North).

Leonard said the first work that motorists will notice as part of phase three will be the modification of the ramps on the Red Mountain Expressway - at the interchange with I-59/20 -- and how the roadway will tie to 31st Street and 12th Avenue.

"We don't anticipate any major (traffic) impact at this time," he said.

Foundation work will also begin soon underneath the exiting I-59/20 bridges in preparation for their removal, Leonard said.