A change to the design of a new bridge on the Bremen-Bristol town line means up to a week delay but will result in a much stronger bridge, according to Kitty Breskin, a senior geotechnical engineer with the Department of Transportation.
Route 32 has been closed while two culverts are replaced by the bridge spanning Muscongus Brook and the road originally was scheduled to reopen Thursday, Aug. 8. The deadline, however, has been pushed back a week to Thursday, Aug. 15 because of a change to the facing of the bridge’s abutments, Breskin said.
Breskin, who designed the bridge, said it is of a new style that uses soil layered with geosynthetic fabric to create the abutments and is only the second bridge in Maine that uses that design.
The friction of the compacted soil on the fabric limits the amount of load on the facing of the abutments, she said.
The Federal Highway Administration recommends using cinder blocks to create the facing of the abutments, but when the blocks were tried in this project the blocks were “bouncing around” while the soil was being compacted, Breskin said.
“If something is going wrong you need to admit it rather than build it,” she said.
As a result, last Friday a design change to a poured concrete facing was discussed, and Hagar Enterprises, the Damariscotta contractor building the bridge, poured the facings the very next day, Breskin said.
“I can’t speak highly enough of them. I was really pleased,” Breskin said.
Even though the bridge has a poured concrete facing, the facing is still not a structural part of the bridge since the beams sit on top of the soil in this design, Breskin said.
Using soil and aggregate to build the abutments is a cheaper and faster option than making them solely out of poured concrete, Breskin said. Poured concrete takes up to 28 days to set – which would have meant a longer road closure – and since the poured concrete facing is not structural, accelerators were used to help it set up more quickly, she said.
Breskin said she was sorry to have to extend the road closure to accommodate the design change, but new technologies sometimes require tweaking.
“I personally apologize to everyone we’re inconveniencing, but we’re going to get a better bridge out of it,” she said.
