The final weeks of work on the Interstate 20 bridge across the Mississippi River have begun, with expectation that months of limiting traffic to single lanes will end about April 23.

The work to reinforce support piers, a $13.8 million stabilization project, has been under way for more than a year.

Eastbound and westbound lanes have been made more flexible by new connector plates, a process that the Louisiana Department of Transportation and Development said contributed to traffic snarls on the Mississippi side of the bridge last fall as crews inserted the newer, thicker plates. Most of the time, the narrowing of the road has not interrupted traffic flow across the river, but at times jams have backed up cars and trucks for up to six miles.

Change orders to the contract held by Lafayette, La.-based C.E.C. have extended the overall cost by about $50,000 and the completion date by six weeks.

Independent studies have concluded deep underground movement has caused major movement of the piers, particularly closest to the Mississippi side. Separate analyses of the old U.S. 80 bridge to the immediate north have also confirmed pier movement in supports nearest the river’s east bank, prompting concrete and bearings to be replaced three times in the past dozen years.

LDOTD maintains the bridge, opened in 1973. Warren County owns and maintains the U.S. 80 bridge largely through tolls paid by Kansas City Southern Railway.