PRAIRIEVILLE — The apparent low bidder on a 2.2-mile project to widen La. 73 in Ascension Parish from two to three lanes came in $3 million under construction estimates, a state highway spokesman said.

Barber Bros. Contracting Co. LLC submitted a nearly $15.51 million construction bid to widen the stretch of La. 73 between Airline Highway and Interstate 10, according to a Louisiana Department of Transportation and Development bid tabulation.

The construction estimate was $18.5 million.

The widening project is a long-awaited improvement on a stretch used regularly by commuters in one of the fastest-growing areas of Ascension between 2000 and 2010.

Another 2.8-mile stretch of La. 73 between Airline and Bayou Manchac was resurfaced, though not widened, with federal stimulus funding and finished early this year, parish officials have said.

Dustin Annison, DOTD spokesman, said Friday work could start this fall on widening La. 73. The job would last a year and a half if the bid from Barber Bros. is approved and contracts are signed after bids are reviewed, Annison said.

If so, Barber Bros. would have beaten out seven other companies whose construction bids ranged from $15.599 million to nearly $23.7 million, the bid tabulation says.

Barber Bros.’ total bid is $17.3 million, bid tabulations say.

As part of the project, Ascension Parish government would have to install sewer lines under the improved road at an estimated cost to the parish of more than $3 million, parish officials have said.

The rest of the project is being paid for with a combination of state surplus funding from fiscal 2006-07 and 2007-08 and federal Congestion Mitigation and Air Quality Improvement Program money, DOTD and parish officials have said.

Annison said DOTD usually takes two to four weeks to review the bid and select the winner.

The La. 73 bids were let Wednesday at DOTD headquarters in Baton Rouge, the DOTD bid-letting webpage says.