The City of Saint John raised worries last December that an expanded Mackay Highway could lead to more traffic and impact the Renforth bog.
The city outlined its concerns over the proposed widening of the Mackay Highway during the environmental review phase of the project.
The New Brunswick government is still weighing the environmental impact of the plan to widen the Mackay Highway from Rothesay into the city.
Many Saint John residents and politicians have started to oppose the project saying the wider highway could cause more people to leave the city as there would be fewer traffic headaches.
Shane Galbraith, the city's director of public works, said there is a concern that a better highway may lead to more traffic.
"There is a tendency, if you build it they will come," he said.
An increase of cars travelling between Saint John and its neighbouring communities may also pose a series of environmental concerns.
"We have a general concern with possibly increasing traffic, or potentially increasing the number of vehicles on the road and the impact of greenhouse gas emissions on the Saint John region generally," Galbraith said.
The Department of Transportation says 33,000 vehicles use the Mackay Highway daily. The department expects that to increase by 2.5 per cent in the next two to three years.
The document filed by the city also listed a concern about the impact the plan would have on an area known as the Renforth Bog located next to the highway.
"That area, headwaters to the Marsh Creek, it's rather pristine," Galbraith said.
"We had a concern that this project and the access road associated with it would produce more impact, or the potential for more impact, and human activity in that area."
But Transportation Minister Denis Landry says the construction project has already been announced and there is no stopping the highway expansion.
Landry says there is more traffic coming whether the road is widened or not.
"We can expect in the future to have more cars, more vehicles a day, on that same section of road there," Landry said.
The transportation minister said Dexter Construction, the contractor involved with the project, will get all the environmental approvals it needs before it begins to do any work.