Three replacement bridges will be built alongside deteriorating spans in the Zoo Interchange, in a quick and temporary fix that will cost $15.3 million, according to a contract detailed by the state Department of Transportation on Monday.
Milwaukee Constructors LLC will start work on Jan. 4 and have the new bridges open for traffic by May 24, with very limited traffic disruptions during the construction, under the agreement with the DOT.
Milwaukee Constructors LLC is made up of Edward Kraemer & Sons Inc., Lunda Construction Co. and Zenith Tech. The same three contractors teamed together and received more than $413.7 million for work on the Marquette Interchange, completed in 2008.
The consortium of Wisconsin-based firms submitted the only bid for the emergency work in the Zoo Interchange and proposed to build the replacement spans for $11.3 million.
The price increased by $4 million during negotiations, as the DOT sought to limit the ramp and lane restrictions during the construction, according to Paul Trombino, operations director for the DOT highways division.
Full traffic closures on the bridges being replaced and the roadways under them will be allowed on only one weekend - for each ramp - during the project. Traffic restrictions on single lanes and the shoulders will be limited primarily to nighttime hours, according to Trombino.
"The way we've constructed the work, with the restrictions, this is fairly unique for Wisconsin," he said. "The Zoo Interchange is unique in Wisconsin, with the level of traffic that comes through there.
"We're very confident with the contractor we have, that they're going to deliver the work."
The Zoo Interchange on the west edge of Milwaukee connects I-94 and I-894/U.S. Highway 45, major east-west and north-south routes for commuters and commercial traffic in the state. Roughly 350,000 vehicles pass through daily, making the Zoo the busiest interchange in Wisconsin.
Its ramps and bridges are now more than 40 years old and are showing their age, particularly the three spans the DOT has determined won't last until a full reconstruction can be started around the middle of the decade. Inspections conducted over the summer showed three bridges in the interchange required immediate replacement because of severe cracks in the concrete girders, corrosion that weakened the steel reinforcing bars and concrete falling from the bridges.
Weight limits were imposed on the bridges in August, and the DOT sought bids for the emergency replacements in November.
Officials estimated the project would cost $12 million to $22 million for bridges that will be in place for less than a decade. They will be torn down in the full redesign and reconstruction of the interchange, which is still being planned.
The new bridges will replace the span that carries traffic northbound on Highway 45 through the interchange, the ramp carrying traffic from northbound Highway 45 to westbound I-94 and the ramp connecting southbound Highway 45 to eastbound I-94.
In a more traditional construction, the old bridges would be demolished and traffic would be detoured until the new spans were finished.
To keep traffic flowing, Milwaukee Constructors will build the new bridges immediately adjacent to the spans they are replacing. Traffic will be re-aligned onto the new ramps, and the old structures will be demolished after the new ones open.
States have begun to seek such alternatives to limit the disruption on congested roadways. In planning meetings, the DOT reviewed options that included building new bridge spans near the interchange and using self-propelled transporters to move them into place in one weekend.
The alternative proposed by Milwaukee Constructors eliminates the need to hire a transport company and uses more conventional construction methods.
Mary Lou Ralls, a national expert in rapid construction, said it appeared the DOT and the contractor had found a reasonable approach to replace the deteriorating bridges.
The former Texas bridge engineer said it would have been preferable to have the competition of multiple bidders, but the goal of completing the project in a short time frame should be met.
"It's not an ideal situation," she said. "For them, in that environment, in that location, that may be the best they can do."
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