Norwich — A new plan to replace the deteriorating Sherman Street Bridge over the Yantic River — called the Canada Bridge — and a second smaller span over the adjacent former mill canal would move the bridges some 200 feet north, creating a new intersection at Asylum Street at a wider spot along the Yantic River.

The $14 million plan would replace an earlier design in the works for several years that called for replacing the two bridges in their existing locations. But Public Works Director Ryan Thompson said the earlier plan would cost an estimated $10 million and wouldn't solve persistent elevation and flooding problems.

The project would be funded 10 percent by the city, 10 percent by the state and 80 percent by the federal government.

The poor condition of the 60-year-old bridges forced the Public Works Department on Oct. 27 to downgrade the weight limit over the canal bridge from 20 tons to 10 tons — allowing short-box delivery trucks, snow plows and school buses, but not 18-wheeler trucks or large, heavy cranes.

The bridges are inspected by the DOT every six months, instead of the normal two-year inspection schedule for local bridges. The Public Works Department also recently repaved the canal bridge to repair crumbling asphalt.

Thompson said the new design, which would need approval by the state Department of Transportation and Department of Energy and Environmental Protection, emerged during a recent meeting with the project's engineering firm, WMC Consulting Engineers of Newington.

If approved, permitting could take two to three years, and construction another two years, Thompson estimated.

The new design would resolve complex problems with the two bridges. After heavy rains, snow or ice melts, the water rushes through the bridge abutments, and the water level can reach the underside of the bridge.

The original plan included a proposal to remove the middle section of the historic granite Upper Falls dam on the Yantic River a short distance downstream. But Thompson said removing the dam would only reduce water levels by 6 inches. Because of the minimal impact, Thompson said the Federal Highway Administration might not cover that cost.

New bridges in the same location could only be 3 feet higher than the existing spans, because of the elevation of Asylum Street, Thompson said, and would requiring taking portions of at least three residential properties across Asylum Street. Any higher, and the homes themselves would have to be taken, Thompson said.

The proposed new span would be located on city land at a wider spot on the river. The new bridge would be about 175 feet long, verses the existing 60-foot long main bridge, and would end atop a rocky island that divides the river from the canal. The second canal bridge would be about the same length as the current shorter span.

The preliminary design would require taking only a small portion of the parking lot of the Haitian Health Foundation at 97 Sherman St. at the end of the canal bridge. The driveway entrance to the Upper Falls Heritage Park would be lengthened to meet the new roadway just over the canal bridge.

With the new plan, traffic would not be disrupted during the estimated two-year construction period, whereas a circuitous detour would be needed to get across the river if the existing bridge were to be closed and replaced.

c.bessette@theday.com

Twitter: @Bessettetheday