Norwich — A project that has been designed and redesigned over the past decade now is on the calendar for construction to begin April 1.

The city advertised for bids last month for a contractor to replace two bridges on Sherman Street that cross over the Yantic River. Bids are due Jan. 19, and construction on the project is expected to start April 1 and run through fall of 2023.

The project will replace the main bridge, which dates to 1955, as well as a smaller bridge over an adjacent river canal. The larger bridge was built in 1955 and is rated in poor condition by the state Department of Transportation, with the substructure labeled as satisfactory. The smaller bridge was built in 1920 and reconstructed in 1964 but is rated even lower at “serious” condition with a substructure in poor condition.

The estimated $10 million project — paid for with 80% federal funds, 10% state funds and 10% city money — likely will cause traffic headaches for everyone from city residents to ambulance drivers, school buses and students walking to Norwich Free Academy from Asylum Street and nearby neighborhoods.

The Sherman Street bridge is a major crossing point over the Yantic River, and detours will take drivers miles away along New London Turnpike to Norwichtown or West Main Street into downtown.

“It’s going to be a challenge,” Police Chief Patrick Daley said of the traffic. “We expected it to be a challenge. I hope the public is patient and cooperative. There’s no easy detour, because it’s crossing a river.”

Public Works Director Patrick McLaughlin said city officials have been talking to school system officials about the pending construction and detours.

Construction is slated to begin April 1 with utility work on the Asylum Street side of the bridge before the bridge is completely closed to traffic for the majority of two construction seasons in 2022 and 2023, McLaughlin said. During the winter of 2022-23, the bridge will be reopened as construction shuts down, but it will close again in spring of 2023 until completed.

The project calls for replacing the two spans with one “clear span,” which will be raised up 18 inches to avoid potential damage by the flood-prone Yantic River.

Currently, a large sewage pipe is suspended from the bridge, exposed to the weather and potential damage from flood-borne debris rushing by beneath the bridge. The project calls for incorporating the sewage pipe into the new bridge substructure, which will be “a huge help” to better protect the pipe, Norwich Public Utilities spokesman Chris Riley said. NPU will construct a pump station on the Asylum Street side of the river as part of the project.

Riley said all four city utilities, water, sewer, electricity and natural gas, cross the Sherman Street bridge. All four services will be upgraded and modernized with the new bridge construction.

The bridge also will be shifted slightly to the north to better line up the intersection with Asylum Street, which now features a sharp right turn from Sherman onto Asylum, difficult for school buses and trucks. Asylum Street will be raised about 18 inches at the intersection as well to match the height of the new bridge, McLaughlin said.

The three-way stop signs at the Sherman-Asylum intersection installed several months ago will remain in place. The three-way stop was planned as part of the bridge replacement, but the city installed the two new Asylum Street stop signs early, and McLaughlin said it has worked well to ease traffic turning from Sherman onto Asylum Street.

The sidewalk on the new bridge will shift from the north side to the south side of the bridge.

During construction, the vehicular entrance to the Upper Falls Heritage Park, on Sherman Street just past the bridge, will be closed. The park will remain open to pedestrians through a stairway access a bit farther up Sherman Street.

c.bessette@theday.com