A state engineer says weather is the “wildcard” when it comes to whether or not the Main Street Bridge in Niles will open to traffic this year.

Chris Jacobs, engineer with the Michigan Department of Transportation, said the project is about four weeks behind schedule, meaning the bridge would open sometime in mid-December.

Original estimates had traffic moving on the bridge by mid-November.

“They (contractors) are 100 percent committed to trying to get it open this year, but weather is going to be the wildcard,” said Jacobs.

On Monday, workers were busy placing the last of the 21 beams on the bridge with the anticipation that they would all be placed sometime today.

After that is done, Jacobs said crews would begin constructing “back walls” on each of the two abutments. Made out of steel reinforced concrete, each back wall “ties” the beams to the abutment.

Jacobs said they would begin on the west abutment and move across the bridge placing concrete and steel reinforced diaphragms between each of the beams at both of the bridge’s two piers.

“A lot of these operations will be going on at the same time,” Jacobs said. “From start to finish it will take approximately two (or three) weeks to go from abutment A (west side) to abutment B (east side).”

From there, Jacobs said workers would begin forming the deck, or the roadway surface above the beams.

“Once we starting working on the deck we should have a much better idea (of our time frame), especially when we see what the weather is doing,” said Jacobs, adding that the substructure (abutments and piers) is finished.

Jacobs said contractors can work on substructure all year long without many problems.

When it comes to the superstructure — essentially everything above the abutments and piers — that isn’t the case.

Jacobs said they would be using different grades of concrete for the superstructure that are sensitive to temperature.

“If the weather turns on us we have to do a lot more things to ensure that concrete is protected and doesn’t have any premature defects in it,” Jacobs said. “It will take longer and will cost more money… they will have to heat and house, use thermal blankets. There are lots of different things we will have to do, but then again that slows things down.”

The MDOT project to build the new bridge is expected to cost approximately $10.6 million.

The new bridge replaces one that stood for 90 years. Work to demolish the bridge and build a new one began in October 2014.