Construction on Sunset Street Bridge will start by the end of the month, Dale Rademacher, the director of Longmont’s public works and natural resources department, told the City Council on Tuesday.

The bridge was damaged in the September 2013 flood and the city has been working with Boulder County, the Federal Highway Administration and the Colorado Department of Transportation ever since. The goal is to replace it with a bigger bridge that should be able to withstand 100-year flood flows.

The bridge has been a flashpoint in the community, with many residents wondering why the bridge remains closed more than two years after the flood. City officials have said that the joint decision between Longmont and Boulder County to completely replace the older bridge instead of repair it at a higher cost, as well as working within the constraints of state and federal grant requirements is why the bridge construction is starting in 2015.

“I know a lot of folks, myself included, have been frustrated in the time it has taken to start the bridge,” Rademacher said. “But the time it took to convince the Federal Highway Administration to build back not only what was there, but a bigger and better bridge, I think was time well spent.”

Rademacher said that the city has contracted with Broomfield-based Flatiron Construction for the project, for a total cost of roughly $3.4 million. The Federal Highway Administration will pay for roughly 83 percent of the cost, while the county and the state will split nine percent and the city will take on 8 percent of the cost.

“So if you think of that as eight cents on the dollar, I think we’re getting a pretty good deal,” Rademacher said.

While the old bridge is 90 feet long and 30 feet wide, the new bridge will be 220 feet long and 50 feet wide, partially to accommodate a wider St. Vrain river channel as part of the Resilient St. Vrain project and to add sidewalks and bike lanes. Resilient St. Vrain aims to widen the river channel in several places in and around Longmont, reducing the flood plain and encouraging development along the river banks in the core part of Longmont.

Construction is set to start Nov. 30, and project manager Tom Caprarella said people can expect to see heavy machinery and personnel. The bridge is expected to be completed by early May, he said.

While the bridge has been closed to vehicular traffic, the city o pened it up to pedestrian and cyclist traffic in November 2014. The bridge will again be closed to pedestrian and cyclist traffic starting the week of Nov. 30 and while construction is going on through May, Caprarella added.

Rademacher said that the replacement of Sunset Street Bridge coincides with the replacement — one half at a time — of Main Street Bridge.

“Sunset should go a lot quicker and easier than Main Street because we’re keeping Main Street open while we’re rebuilding it,” Rademacher said.

Karen Antonacci: 303-684-5226, antonaccik@times-call.com or twitter.com/ktonacci