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Zoo Interchange


The Interchange as seen from eastbound I-94

The interchange is scheduled for major rebuilding in 2016, but three spans are so badly deteriorated that they must be replaced soon.

Photo taken by J.R. Manning in November 2009


BH Photo #149624


Street Views 

Emergency Rebuilding of Three Zoo Interchange Bridges Required 

Written by J.R. Manning

The Wisconsin DOT announced, in mid-November of 2009, an aggressive plan to replace three seriously deteriorating bridges, located in Wisconsin's busiest freeway interchange, by Memorial Day, 2010. Plans are to use building techniques that replace each bridge over a weekend, to minimize traffic impact.

The interchange, built in 1963, carries upwards of 350,000 vehicles per day. During the summer of 2009, WisDOT detoured large trucks around the interchange because of severe weight limits that were implemented. The interchange, located in western Milwaukee County, carries I-94, I-894 and US 45.

In a press release, Wisconsin DOT said, "Thorough investigations of the bridges conducted over the past three months show significant deterioration that prompted WisDOT to move forward immediately with plans to build new structures at the three locations."

Requests for proposals are out for ways to accomplish this monumental task. One plan calls for building the bridges at another location and swaping new for old over a weekend.

As you might guess, the politcal slings and arrows started flying around hot and heavy since this announcement was made. Without getting into the political fray and finger-pointing, the characters include Governor Jim Doyle, who is not running for re-election in 2010. Two candidates for the governor's chair are from the Milwaukee area, the Mayor of Milwaukee and the Milwaukee County Executive. Each has, as you might expect, differing views of the issue. The Zoo Interchange flap is already appearing to be a major issue in the 2010 gubernatorial campaign.

There are three major freeway interchanges in Milwaukee County, the Marquette Interchange is downtown, the Mitchell Interchange is on the south side and the Zoo Interchange is on the west side. Three major highway projects were identified in the early part of this decade to rebuild the freeway system in Milwaukee County, as well as the I-94 corridor between Milwaukee and the Illinois state line. The Marquette Interchange was determined to be the most pressing need, followed by the Zoo Interchange, followed by the rebuild of the north-south I-94 corridor to the state line.

The Marquette Interchange was rebuilt between 2004 and 2008 at a cost of $800 million. When the project started, the political wrangling over the Zoo Interchange and the I-94 rebuild started. I-94 won, the project is underway as of this writing. The Zoo rebuild was pushed back to 2016, estimated to be a $2.3 billion project.

Meanwhile, the deterioration of three Zoo Interchange bridges is significant enough for the emergency rebuild of the spans. Inspections revealed severe cracking in concrete with subsequent rusting of steel beams and rebar, and concrete has been falling off the bridges. Further reports tell us the emergency replacements, with a budget of $12 to $22 million, will themselves be replaced during the rebuild in 2016.

Inspired by the work on the San Francisco Bay Bridge, where a span was built adjacent to the extant span, then moved into place over a weekend, the Wisconsin DOT decided such a technique would be best to replace the weakened bridges. The concept of building a span beside the original, then moving the replacement span into place with cranes, has been implemented in Oregon and Utah but never in Wisconsin. DeWayne Johnson of WisDOT says the technique will work. "It has worked elsewhere, it will work here."

Taxpayers, meanwhile, will be expected to foot the bill for up to $22 million to replace the three bridges, only to pay to have them replaced again during the 2016 interchange rebuild. That fact was not missed by State Senator Ted Kanavas (R-Brookfield). "Now, we're going to have to pay twice for bridging and we're going to rip these things out in five to seven years, when we get started on the Zoo [Interchange]."

According to WisDOT, the bridges to be replaced include a northbound span, which carries US 45 from I-894 across I-94 and carries over 42,000 vehicles per day. The othe two spans include the ramp that carries southbound US 45 traffic to I-94 eastbound, used by over 26,000 vehicles per day and the ramp that carries northbound I-894 traffic to westbound I-94. That bridge carries over 25,000 vehicles per day. The Zoo Interchange is the busiest in Wisconsin.

More updates will be posted as this story unfolds.


Interchange of I-94/I-894/US 45
West Allis, Milwaukee County, Wisconsin
Open to traffic
Future prospects
Major rebuild planned circa 2016; emergency replacement of three bridges scheduled for 2009-2010.
Built 1963
Concrete deck girder
Approximate latitude, longitude
+43.02740, -88.03475   (decimal degrees)
43°01'39" N, 88°02'05" W   (degrees°minutes'seconds")
Approximate UTM coordinates
16/415696/4764376 (zone/easting/northing)
Quadrangle map:
Inventory number
BH 43654 (Bridgehunter.com ID)

Update Log 

  • May 23, 2010: New Street View added by Nick Brnot
  • May 8, 2010: New photo from J.R. Manning
  • March 26, 2010: Updated by J.R. Manning: Added satellite image
  • November 21, 2009: Essay added by J.R. Manning


  • J.R. Manning - thekitchenguy [at] sbcglobal [dot] net


Zoo Interchange Didja ever wonder what a "concrete box beam" was?
Posted May 8, 2010, by J.R. Manning (thekitchenguy [at] sbcglobal [dot] net)

The three suspect bridges in the Zoo Interchange have been replaced. The new bridges are on line and the old bridges are being removed this weekend.

Here is what was left of the southbound US 45 to eastbound I-94 bridge earlier this week. If you ever wondered what a concrete box beam was, this photo should clear up the mystery for you.

Zoo Interchange
Posted April 8, 2010, by Nathan Holth (form3 [at] historicbridges [dot] org)

I agree. The concrete would last a LOT longer than it does if we didn't dump salt on our roads. There are already alternatives to salt (chemicals in beets for example) that are friendly to your car, the bridges, and the environment. The only reason we don't use them is probably cost, and perhaps back door lobbying by the auto industry. After all, salt reduces the life of cars. Stop using salt, people won't have to buy new cars as often.

Zoo Interchange
Posted April 8, 2010, by Anonymous

The reason all these bridges deteriorate so quickly can be blamed mostly on one thing: Road Salt. If we were smart, the next generation of bridges should have geothermal heat systems built into them so they last longer. Road salt destroys private property (cars) and public property (infrastructure) Anyone ever heard of SNOW TIRES! We dont need salt!

Zoo Interchange
Posted March 27, 2010, by J.R. Manning (thekitchenguy [at] sbcglobal [dot] net)

Craig, along those same lines, Charles Whitney designed bridges that were inspired by, and modeled after, English Renaissance bridges. The bridges were mostly built in the 1930s out of (drum roll, please) concrete.


The model bridges, built in the 15th and 16th centuries, are still standing and still in use. Whitney's bridges, built in the 1930s, are in need of major rebuilding. The Range Line Road Bridge http://bridgehunter.com/wi/milwaukee/P40070000000000/ shows a Sufficiency Rating of 67.5 and is listed as structurally deficient.

I do hope the Range Line Road Bridge is restored and not just replaced with a UCEB as it is a beautiful structure that deserves to be preserved for future generations.

Zoo Interchange
Posted March 26, 2010, by Craig Philpott (cphilpott [at] puc [dot] edu)

Mostly irony. Reinforced concrete was first patented in 1867 (according to the internet). This structure was constructed nearly one hundred years after that and now it must be replaced after forty seven years of use. It seems to me that the Romans used various forms of un-reinforced concrete more then a thousand years ago and many of those structures, including some viaducts and bridges are still standing. Progress?