Completion of a new drawbridge connecting North Hero and Grand Isle will be delayed by a year because of soil contamination, the Vermont Agency of Transportation announced this month.
VTrans found lead, polychlorinated biphenyls (PCBs) and hexavalent chromium in the soil around the bridge site in July, construction engineer Jeremy Reed said Monday.
The new bridge, part of a key thoroughfare in the Champlain Islands, was initially expected to be complete in May 2021. Now, according to an announcement from VTrans on Jan. 7, it is expected to open for travel in summer 2022. A temporary bridge has been in place since May.
VTrans does not yet have an estimate for how the soil abatement will impact the total cost of the project, which was initially slated at $60 million. Any additional costs, Reed said, would come from VTrans’ bridge program.
The original bridge, built in 1953, was demolished last summer. Reed said the soil contamination was detected as the old bridge was being demolished, which forced a shift in the construction schedule.
Reed said VTrans staff had a contingency plan in place should lead be found around the site.
The agency wasn’t sure soil was contaminated before construction started, but anticipated the presence of lead, due to lead paint on the original bridge.
The presence of PCBs and hexavalent chromium, however, were unexpected.
The other chemicals were detected by tests conducted when the state was working on a plan to address the lead. The contaminated soils are found on the banks of the channel where the bridge lies and in sediments under the water.
At high enough levels, lead can have multiple human health effects, including lower IQs and developmental disabilities in children. At high concentrations, PCBs and hexavalent chromium can cause cancer.
Reed said the levels found on site are “well below” the threshold to qualify the soils as “hazardous waste” and are currently categorized as “soils with contamination.”
“Certainly nothing you want to necessarily make a sandbox out of, but it’s not hazardous waste at these levels either,” Reed said.
Reed said VTrans “immediately” reached out to the Vermont Agency of Natural Resources, which is now collaborating in conjunction with the U.S. Environmental Protection Agency to remove and dispose of the contaminated soils.
To remove the contaminated soil, Reed said crews are currently working to install a cofferdam, a “rigid steel structure” that pushes water out of its way and allows crews to access soils below the water line to remove the contaminants.
Crews will also continuously test the soils below the water until no contaminants are found.
“Then, we will generally be in a place to build a bridge as we typically would,” Reed said.
Reed said bridge projects are more sensitive to delays than other road work or building construction. There are winter work restrictions in place now and the United States Coast Guard has regulations which mandate a navigable waterway must be maintained during peak boating season in the summer.
These restrictions, Reed said, can exacerbate a delay in the project. A discovery like contaminated soil may only delay a building or road work project by a few months, he said.
Aspects of the construction require crew members to occupy the waterway underneath the bridge, which Reed said is not doable during summer months, leading to a longer delay.
“There are certain activities that are sensitive to weather and environmental factors and we didn’t want to, in any way, impair quality by trying to force those activities to occur in, say, January,” Reed said,.
Since the temporary bridge is in working order, Reed said residents should not expect any significant impact on travel.
“We are working collaboratively with our bridge contractor, Cianbro, to ensure that the project proceeds in a safe and environmentally responsible manner,” VTrans Chief Engineer Wayne Symonds said in a statement regarding the delay. “At the same time, our goal, as always, is to build a quality bridge that will last for the next 100 years.”
The 1953 bridge had outlived its useful life, and deteriorating mechanics led to difficulties opening or closing the bridge. It had become imbalanced and its counterweights sometimes dipped into the water. Reed said VTrans decided to replace the bridge rather than repair it because fixing the mechanical elements would have cost more than building a new bridge.
The total project will now last until the summer of 2023. The temporary bridge and road will be removed after traffic is moved to the new bridge.
In 2018, an average of 3,000 vehicles traveled the bridge each day, Reed said.
Read the story on VTDigger here: Champlain Islands drawbridge replacement delayed by one year.
