How Do Milwaukee's Movable Bridges Work?

Jun 29, 2018

If you live, work, or drive through downtown Milwaukee, chances are your route has been interrupted by the sound of a dinging bell and the bellow of a horn as a bridge prepares to allow a boat pass.

After all, Milwaukee is home to 21 movable bridges, which cross the Menomonee, Kinnickinnic, and Milwaukee rivers.

Listener Kate Riordan’s remembers a bike ride that was interrupted by a bridge lifting, and she noticed something that caught her interest and inspired this week’s Bubbler Talk:

“As the boat was approaching the next bridge, it kind of seemed like the bridge was not going up, so I was wondering how exactly do the bridges work? Is it something the boat communicates to the bridge? Is there a person in there watching? Is there some kind of sensor?”

To find out, we visited the Michigan Street bridge house. If you’ve ever noticed these little towers attached to the bridges, there’s actually a person in some of them.

“That would be Broadway, Water Street, Michigan, and Kinnickinnic. Of those four bridges, most of the other bridges are operated remotely,” explains James Washington of the Department of Public Works.

Milwaukee is home to two different types of bridges that lift. A vertical – or table top bridge – moves directly up and down, similar to a lift you would see in a mechanic’s garage.

“There’s an electric motor that’s connected to a large hydraulic pump and they activate the cylinder which actually lifts the jacking beams - these are beams that support the entire lift span on each side of the river," Washington explains.

The other type of bridge is a bascule – the classic drawbridge style in which two platforms open in the middle to let boats pass. The bridge on Kinnickinnic Avenue is one of those, and happens to be the fastest bridge to open and close in town.

The South 1st Street bascule bridge over the Kinnickinnic River was built in 1958 and is anticipated to be rehabilitated in 2017/2018.
Credit City of Milwaukee

The city's movable bridges have been constructed over several generations. The oldest bridge is located at North 16th Street and was built in 1929. The newest bridge at East Juneau Avenue was constructed in 2012. With such a wide range in construction ages, maintenance is important.

Basic routine yearly maintenance involves greasing, maintaining oil, and maintaining the hydraulic systems of the bridges. And, all of them need an overhaul every 40-45 years, which is why the Wells Street Bridge is currently closed.

But back to Kate Riordan’s question – how do they decide when to open the bridges? 

Credit Ben Binversie

The Michigan Street, Wisconsin Avenue, and Wells Street have the lowest clearance of all the lift bridges in operation. Overall, clearance under the bridges ranges from 10 to 24 feet, according to Washington.

But he adds that, that can change from one day to the next. "One of the main limiting factors is the level of the river, and if we have a big snow fall in winter or a heavy rainfall – the levels could be higher.”

However, what doesn’t change is that the bridges open whenever a boat needs to pass through.

"The rivers were here first, so the river technically has the right of way."

“The way that the regulations are currently written is that the rivers were here first, so the river technically has the right of way,” Washington says.

According to the City of Milwaukee, there were 23,000 bridge openings last year alone. One bridge can have up to 50 openings on a single busy Saturday during the summer.

With so many openings, the sound of the warning bell can cause some anxiety for drivers and pedestrians alike.

Riordan shares one particular memory: “I remember as a child my family would do the Miller Ride for the Arts, and we would bike from our car to the starting point and I was always terrified of the bridges. Because I thought that they would just start going up while I was on there and I’d be stuck in the middle or fall into the river!"

The DPW’s James Washington says Kate and everyone can rest assured that won’t happen.

A lead bridge worker controls the Saint Paul Street bridge from the Michigan Street bridge house. In addition to computer controls, there are video monitors to make sure the bridges are clear before any operations.
Credit Audrey Nowakowski

“Sometimes you’ll have someone that starts to cross the bridge as we get ready to turn the bells on. If that happens, we do allow those people to pass so there’s not going to be an incident where you’d be walking and then all of a sudden the bridge starts raising and you go sliding down.”

So now that we know how the bridges work, and there’s no need to worry about getting stuck on a rising bridge. We just need to have a little patience so that we can all get where we need to go – whether by land or by water.

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