While the North Avenue bridge has reopened to traffic, it is still an "active construction site," according to Stephen Edwards, public works director.

The bridge was closed to traffic for the past six months while the $980,000 reconstruction job was underway.

But even though traffic has resumed flowing, some work remains on the project, including installing guard rails and completing masonry work, Edwards said Friday.

"That could mean alternating one lane while they do those jobs," he said.

The work on the 56-year-old concrete span, which crosses the Aspetuck River, included widening it by 6 feet to allow for two, 12-foot wide travel lanes and a new 4-foot-wide sidewalk, according to Sydney Smith, of Diversified Technology Consultants, the business that designed the new bridge.

A new water main and fire hydrant were also installed to service the area, he added.

One of the challenges engineers faced was determining how to repair the bridge's structurally deficient superstructure, said Smith.

He said the replacement structure needed to be constructed in the least amount of time to minimize the time the traffic detour was required.

But Edwards said the bridge closure did not have "a tremendous impact" on the entire town because it is "one of the most outlying bridges."

He said the North Avenue Bridge "doesn't pick up a lot of traffic," but its closure did affect "access for those in the area into the downtown."

Smith said that, after performing hydrologic and hydraulic evaluations in the river, DTC engineers determined enhancements were also needed to protect the structure from river scour and create a viable fish habitat during periods of low flow.

"They came up with a three-part process to correct the problem" which included installing a concrete-block revetment system directly into the stream bed and a rock weir in order to reduce bank erosion and provide "a tranquil pool for fish migration," Smith said.

"The Aspetuck River at this location experiences high river velocities, making the bridge susceptible to failure due to scour," said J. Andrew Bevilacqua, DTC civil engineering manager. "The addition of the block revetment and rock weir provide necessary scour protection, while still being sensitive to environmental concerns."

The cost of the project was 90 percent funded by the federal government's local bridge program, and 10 percent funded by the town, said Edwards.

The construction was administered by the state Department of Transportation, Smith said.