Work to build new bridges over the Kansas River will force a monthlong closure of a popular recreational trail alongside the Kansas River.

The levee trail in Lawrence Riverfront Park, which runs along the northern side of the river, will be closed beginning today at the point where the Kansas Turnpike’s existing bridges cross the river. Those bridges are about 1.4 miles north, by trail, from the Massachusetts Street bridge that crosses the river in downtown Lawrence.

Closing a 200-foot portion of the trail is necessary so that crews can build a new section of levee to allow for construction of bridge piers, which ultimately will support a new bridge, said Rex Fleming, project engineer.

The initial monthlong closure will be followed up with intermittent — likely weeklong — closures through the end of May, he said. Those temporary closings will allow for cranes to lift large bridge beams — each weighing 20 tons — into place.

It’s no place for walkers, runners or cyclists, Fleming said.

“It’s a safety issue,” he said.

Anyone using the trail will be forced to turn around, Fleming said. One side of the levee is bounded by the river and the construction zone; the other is occupied by Union Pacific railroad tracks.

“We just need to have construction employees in there only,” Fleming said. “For the next few days, there actually won’t be any trail there. It will be being reconstructed. We’ll have equipment all over it.”

The work is part of a $130 million project to replace the turnpike bridges and upgrade the West Lawrence and East Lawrence interchanges. Work on the overall project is scheduled to last into 2011.