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Construction of the temporary work platform at the Milton staging area for construction of the new Milton-Madison bridge is expected to be completed this week. Meanwhile, strengthening of the existing bridge piers continues with steel reinforcement and crack repair. Scaffolding is also being installed on the three water piers that will be retained for the new superstructure. Materials to be used in construction of temporary access ramps on both sides of the river are being delivered to the work sites.
The ramp structure on the Kentucky side is technically called a “trestle,” according to Walsh Construction Project Manager Charlie Gannon. Like the causeway that has been built into the river on the Madison shore the trestle is “a structure that allows us to get out into the water to have enough depth of water to float our barges,” Gannon said.
While the Indiana causeway is a loading facility for materials and equipment to be loaded onto barges, the Kentucky trestle will be used “to preassemble the truss sections that we’re going to float in and lift into place. It sticks out into the water about 120 feet,” Gannon said. A “T” section will be added onto the end.
The trestle stretches out over the water from the Milton staging area which “is going to be our storage and assembly yard for the new truss,” Gannon said. “This will be where we will receive and store all the parts and pieces for the new truss.”
Later in the summer Walsh Construction will erect temporary support towers on the downriver side of the existing bridge location onto which the new truss system will be lifted and placed. These towers will carry the weight of the bridge when traffic is transferred from the existing structure onto the temporary location. Once traffic is rerouted to the new bridge on the temporary towers the demolition of the old bridge superstructure will commence, Gannon said.
The temporary support towers will be “built out of big heavy pipes and big heavy bracing,” Gannon said. “They’ve been designed to withstand barge impacts and all the loads as part of what we’re doing. In early August the truss pieces will start showing up. We’ll bring in some very large barges and begin assembling the sections that will go in span two.”
Work to erect temporary access ramps to each end of the bridge should begin later this month, Gannon said.
“The whole idea of doing the temporary ramp is to tear down the rest of the approach spans in order to build the new approach spans, which become critical to using the new truss in its temporary location,” he said.
The Indiana ramp will begin elevating Vaughn Drive from just east of the last riverfront overlook near the Rivertown Inn in Madison. The ramp will turn and tie-in to the existing bridge at the land-based pier closest to the river. The temporary access ramps will consist of two, 12-ft lanes and have two bends, Gannon said.
“One will be long and the other will be a short one as we tie into the truss section itself. We will build everything we can up to the existing bridge on both sides prior to shutting the bridge down to make those tie-ins. It will be a combination of dirt fill and an elevated roadway supported by our pipe piling.”
The Kentucky ramp will provide traffic access to the bridge via Ferry Street at the Milton boat ramp and will tie-in to the bridge at the last land-based pier on the Milton shore.
During the first bridge closure Walsh will have a demolition contractor remove existing approach spans, Gannon said.
“That section will be dropped and drug out of our way as quickly as possible,” he said, “then we’ll go in and complete the temporary ramp and tie it in to the bridge.”
Once the new truss is completed on its temporary supports short connector stems will be built “to tie-in the new approach bridge to the new truss in its temporary location and use that as access across the river while we demo the rest of the bridge and complete the pier strengthening—which will be applying the new caps,” Gannon said. “Once the new caps are complete that’s when we’ll do our second closure and slide the new truss into its permanent location.”
When the temporary ramps open to traffic, the Kentucky Transportation Cabinet will reduce the speed limit on the bridge from 35 miles per hour to 20 mph, according to KYTC Project Manager Andy Barber. The weight limit will remain at 15 tons.
“Semi traffic will not be allowed on the bridge,” Barber said. “The (vehicle) length restriction will be cut down to 36 feet.”
Large panel road signs will be placed on a detour route to warn truckers that “they can’t come through here,” Gannon said. “They won’t be able to negotiate two of the curves that we’ll have, especially on the Kentucky side. Truckers talk to each other. I think the word will get out pretty quick that you just can’t do this anymore.”
“We do have funding for extra police patrols for the purpose of monitoring traffic,” Barber said.
The date for the first closure of the bridge to connect the temporary access ramps has not yet been determined, Gannon said.
“With the delay that we’ve suffered on this job we’re really looking at that hard right now,” he said. “If we close it this year it’s going to be sometime during the fall. As soon as we revise our schedules as part of our acceleration effort we’ll put the word out.”