Construction is nearly finished on a new 147-foot rolling bascule span that will be installed the last week in April, as part of a $16 million project to replace the Canadian Pacific Railway's century-old swing bridge over the Black River at La Crosse.

Beginning at 7 a.m. Monday, April 26, spectators will be able to watch the work from a public viewing area set aside at the F.J. Robers Co. terminal at 816 S. Bainbridge St. on French Island, just north of the railroad bridge. Public parking will be along Bainbridge Street, railroad spokeswoman Laura Baenen said.

For safety reasons, the Black River beneath the bridge is expected to be closed to all boat traffic from 7 a.m. April 26 until 7 a.m. May 1, said Ray Strelesky, manager of project services at the railroad's U.S. administrative offices in Minneapolis. The railroad's headquarters are in Calgary, Alberta, Canada.

And the bridge is expected to be closed to train traffic from 7 a.m. April 26 to 7 p.m. April 28, then will be closed intermittently until 7 a.m. May 1. When the bridge is closed, train traffic will be rerouted onto other rail lines.

The old swing span will be removed April 26. The new rolling bascule span, which has been assembled at the F.J. Robers terminal, will be floated into place on a barge April 27.

Early in the morning of April 27, explosives will be used to remove two old bridge piers.

Nearby residents probably will hear the blasting. "I would characterize them as thuds," Strelesky said of the sounds.

Once it's operating, the west end of the new span will lift into the air to allow barges and other large boats to pass. The old truss swing span swings open to allow them to pass.

The old span typically has been opening 1,800 to 2,000 times a year to allow the boats to pass.

Small boats usually can travel beneath the bridge without having the span opened, said Bill Hager, Canadian Pacific construction supervisor for the project.

"The new one will be easier to repair and maintain," Baenen said. And it will take two minutes to open, compared with six minutes for the current swing span.

Improvements to the railroad bridge, which is a mile south of the Interstate 90 bridge, will allow train traffic to operate more fluidly between Wisconsin and Minnesota, Baenen said.

The new structure will substantially reduce maintenance costs and provide more reliability in operations, benefiting both the railroad and users of the river, Strelesky said.

Baenen said at La Crosse, about two dozen freight trains and two Amtrak passenger trains a day cross four bridges over the east and main channels of the Mississippi River, the Black River and the French Slough.