Big incentive

Conway interchange replaced with four-lane bridge

By Mark Friedman

Allan Hoover, project manager for Gilbert Central Corp., of Little Rock, is pressed for time.

If he can finish the $9.3 million Interstate 40/Highway 65B interchange project in Conway, Ark., by the end of June, Gilbert Central will receive an incentive of $15,000 a day, up to 17 days. But if he's late, it will cost the company $15,000 a day.

"It's a huge incentive not to finish late," Hoover said.

Gilbert Central began working on the project after Labor Day. The contract calls for the firm to demolish the two-lane bridge over the interstate and build a new four-lane bridge with sidewalks. It also has to build the on- and off-ramps that will connect the bridge to the interstate.

The Arkansas Highway and Transportation Department designed the project to alleviate heavy traffic in Conway, said highway department spokeswoman Farrell Wilson.

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Gilbert first built two lanes of the new 374-ft.-long bridge, then rerouted traffic to the new bridge and demolished the old bridge.

With the old two-lane bridge out of the way, Gilbert is now in the process of building the remaining two lanes. Upon completion, the new bridge will be 18 ft., 5 in. high at its highest point and will have a metal deck topped with a concrete driving surface.

Before construction of the bridge began, Gilbert supported the bridge embankment with an anchor tieback system.

Hoover said Gilbert is using lattice boom and hydraulic cranes to set forms, place concrete and set girders. Nine concrete columns extend about 10 to 15 ft. underground as support.

"After the girders are set, a subcontractor installs the metal decking, which acts as a form for the concrete," Hoover said.

Gilbert is installing a 3-ft., 9-in. overhang to support the outer edge and is using a paving machine to place concrete for the deck.

"Once the overhangs are set, we install our edge forms," Hoover added. "The paver rides on the inside of the bridge and out on the overhang to finish the bridge deck."

The substructure is made of concrete with reinforcing steel and the superstructure has structural steel beams with a concrete deck. The bridge deck will be made of concrete.

With half of the new bridge built, the next phase of the project was demolishing the old bridge.

"We used two track hoes with hoe rams, so we were able to tip the girders off with the track hoe," Hoover said. Demolition took three nights because the work over the interstate could only be done between 10 p.m. and 5 a.m.

With the old bridge out of the way, Gilbert Central is in the process of building the other half of the new bridge, Wilson said.

To connect the two structures, Gilbert will use pieces of angle iron to attach the metal decks of the bridge sections.

"It just creates a joint," Hoover said. "So when we pour the next deck, we'll pour it flush with the first half of the bridge."

During construction of the bridge, work on the on- and off-ramps was also under way.

To build the ramps, Gilbert imported about 70,000 cu. yds. of sandstone and shell rock, followed by 7 in. of limestone aggregate and 13 in. of asphalt. Workers also installed 18- to 36-in.-diameter reinforced concrete pipe for drainage at the ramps, as well as about 25 to 30 inlets.

One of the obstacles of the job has been maintaining traffic flow on the interstate, Hoover said. The Arkansas Department of Highway requires that the eastbound lanes on I-40 stay open from 6-9 a.m. and the westbound lanes have to stay open from 11 a.m. until 7 p.m.

If the lanes are closed, Gilbert Central faces a fine of $2,000 per mile for the first hour and $500 per mile for each hour after that, Hoover added.

To avoid the fines, the contractor has worked a lot of nights.

"We're used to it," Hoover said. "We'll perform whenever we need to get the job done."

He also said the traffic on Highway 65 B caused slowdowns.

"You can see right now that you can't haul a darn thing across the bridge," Hoover added, pointing to the cars creeping across the bridge. In 2004, the bridge saw 2,995 vehicles a day, Wilson said. By 2024, it is expected to carry approximately 49,000 vehicles.

Useful Source

For updates on the project, go to: http://www.ahtd.state.ar.us/Contract/contract.htm