A small, picturesque, city-owned bridge that carries Flax Mill Lane over the Wepawaug River in Milford is still safe and structurally sound, state officials said, but it is obsolete and will be replaced next year.

The Milford Inland Wetlands Agency voted recently in favor of replacing the bridge, which is described as “scour critical,” meaning that it is susceptible to erosion by the river current.

Bridge scour is the removal of material, like sand and gravel, from around the bridge support structures caused by swiftly moving water. In this case, the moving water has created a scour hole that has measured up to 15 feet wide by 16 feet long, exposing a portion of the footing at the northwest corner of the bridge.

“The water has been doing a job on it,” said state Department of Transportation spokesman Kevin Nursick.

The bridge is structurally sound and it is safe, Nursick said. But according to minutes on file with the city and state, the bridge is “functionally obsolete.”

Engineers had looked at rehabilitating the existing bridge, but determined that replacing it is the best option because there is no reasonable way to make it resistant to continued erosion by the water.

“It’s a much better use of funding to replace it with a modern bridge,” Nursick said.

Flax Mill Lane is a short, scenic roadway that connects North Street to West River Street.

The existing Flax Mill Lane bridge dates back to 1935, according to Project Engineer Michael Brady of Close, Jensen and Miller PC in Wethersfield. It consists of two reinforced concrete slabs supported by a stone masonry foundation and a central pier.

Plans call for replacing it with a concrete deck on a pile-supported concrete foundation.

“The precast pre-stressed deck units provide the longest service life and lowest future maintenance costs due to its low susceptibility to water infiltration,” according to notes on file in the city’s Inland Wetlands office.

City documents indicate the new bridge will be slightly longer than the existing one, going from 44 feet to 54.5 feet, and the width from curb to curb will go from 22 feet to 24 feet.

The increased length is to “make sure there is no negative impact on the waterway,” Brady said.

The bridge is not expected to lose its New England charm. A stone veneer will be used to help replicate the look of the existing bridge.

Bid documents are being prepared now, and work is expected to start in April, 2020. The project is expected to take six to eight months, and traffic will be detoured while the work is done.

The project is being done through a Federal Local Bridge Program, meaning that 80 percent of the cost will be paid with federal dollars, and the city will be responsible for the remaining 20 percent.

According to a 2017 DOT memorandum, earlier estimates had the project, including design, rights of way and construction, costing between $2.4 million and $2.7 million.