The Department of Transportation ordered the bridge carrying traffic northbound on US 45 through the interchanged closed after inspectors found an alarming growth in cracks.
Some of the cracks, mapped during inspections last fall, grew by as much as four inches since then.
"The cracks are very indicative of an overloading problem," says Beth Cannestra, the DOT's director of structures.
Weight restrictions have been in place on the bridge -- and two others in the Zoo Interchange -- since last fall, when inspectors discovered severe detererioation on the three bridge decks.
Motion scales were installed to monitor traffic and State Troopers patrolled the interchange, citing drivers carrying overweight loads.
A request for comment on the number of citations issued from the State Patrol was not immediately returned.
Traffic on the now-closed bridge was limited to 30 tons but a review of data collected from the scales showed that the number overweight vehicles using the bridge was growing, some carrying in excess of 100,000 pounds -- nearly twice the posted limit.
"This was not a regular inspection, Cannestra says. "This was totally in response to overloading on this specific bridge. We just saw a total lack of adherence to our weight limit postings."
The DOT did not perform an inspection on the other two bridges in the interchange because similar patterns of disregard for restrictions were not determined to be a problem. Those bridges, which carry traffic from southbound US 45 to eastbound I-94 and to I-894 aren't used as heavily and had higher weight restrictions in place.
"We have not seen parallel overloading on the other bridges," Cannestra says. "We will continue to monitor those, though, and if we start to see similar patterns, then we'll do an inspection on those bridges, too."
The Zoo Interchange, built 50 years ago, is the state's busiest interchange, carrying roughly 350,000 vehicles daily, and it connects drivers with the Fox Valley as well as Madison and northwest Wisconsin.
Plans to rebuild the interchange beginning in 2012 were put on hold when Gov. Jim Doyle withdrew funding for preliminary engineering work from the current state budget.
When deterioration was discovered last year, plans for weight restrictions and the temporary spans were put into place and the DOT awarded a $15.3 million contract to Milwaukee Constructors, LLC -- builders of the Marquette Interchange.
Milwaukee Constructors is building three new bridges alongside the exisiting ones, with traffic being rerouted onto the new spans once finished.
Concrete pouring for the northbound bridge deck was already scheduled for early next week, but the DOT is working with contractors in an effort to accelerate the schedule, which called for all three bridges to be finished by Memorial Day weekend.
"We've been in contact with our contractors but there is no conclusion yet," Cannestra says. "Certainly, it's in everyone's best interests to accelerate the construction of the bridge."
Detour route: The marked detour will carry northbound traffic onto eastbound I-94 to S. 84th St., where it will exit, turn around and re-enter westbound I-94 and then rejoin northbound US 45.
In addition to the bridge closure, the northbound on-ramps at Greenfield, Lincoln and National Avenues will be closed. Portions of S. 84th St. will also close to help with the flow of detoured traffic.
Traffic from northbound I-894 can still use the Zoo Interchange ramp and bridge to westbound I-94.
To assist drivers, the DOT is deploying a number of portable message boards to supplement the overhead signs throughout the area.
Drivers on northbound I-43 -- the Rock Freeway -- are urged to use Moorland Rd. and eastbound I-94 as an alternative to I-894. Locally, S. 76th Street to W. Bluemound Rd. or W. Wisconsin Ave. will steer motorists clear of the closure.
"If travelers are coming through the interchange, they should give themselves extra time; it's going to be slow," Cannestra says. "Drivers can avoid frustration by using alternate routes."
Motorists can call 511 from their mobile phones or log on to 511wi.gov for more information.
Bus routes affected: The Milwaukee County Transit System has made changes to two Freeway Flyer routes and one regular service route due to the closure.
Flyers 45 (Watertown Plank) and 79 (Menomonee Falls) will now travel west on Wisconsin Avenue before proceeding north on US 45. No stops will be affected, but riders should expect to add time to their evening commute.
Route 67, which serves S. 84th St., will also be slightly detoured. Northbound buses will travel west on Schlinger Ave. to 92nd. St. St., travel north on 92nd St. to Bluemound Ave. and east on Wisconsin Ave. back to 84th St. Southbound buses will follow the same route in reverse.
