GOVERNMENT: EMERSON BRIDGE CONSTRUCTION TO ENTER NEW PHASE TUESDAY

A steel caisson larger than a river barge is stationed in the middle of the Mississippi River, ready to begin a descent that eventually will end 50 feet below the river bed.

The procedure, to begin Tuesday inside the coffer dam at pier 3 of the new Bill Emerson Memorial Bridge, is considered a milestone in the construction of the bridge.

"It's significant," says Scott Meyer, district engineer for the Missouri Department of Transportation. "We have fixed the fissures and we're back to constructing the pier."

Meyer referred to fissures discovered in the bedrock after construction began. The fissures have been filled with concrete, a process that added $4 million to the cost and a year to the completion date of the project.

Meyer said the work on pier 3 is considered critical to finishing the bridge as projected in 2003. "Pier 3 is what we call the critical path of the bridge, the path we need to do in order to complete the bridge," he said. "Any time you lose time on the pier it adds time to the project."

A caisson is a watertight enclosure construction can be done inside. The caisson walls are like a honeycomb that concrete will be poured into. As more concrete is poured, the weight will put pressure on the sand below. Cranes using buckets will remove sand from the chambers of the caisson grate, allowing the cutting edge of the caisson to sink deeper and deeper into the riverbed over the next few weeks as more concrete is poured.

Meyer said this technique is used only for very large concrete footings.

The work is being done in a "partnering" between MoDOT and the contractor, Traylor Brothers.

The pier is one of a number the bridge will have. Pier one is at the approach area on the Missouri side, near the intersection of Sprigg Street and the Shawnee Parkway. That will be the point where the cables stop. Pier two is at the banks of the river on the Missouri side and has been poured.

Pier four is to be located near the riverbank on the Illinois side and has yet to be built.

Repairs continue to the roadbed of the existing Mississippi River Bridge. During the beginning of this phase of construction at pier 3, traffic on the bridge will be reduced to one lane from noon-5 p.m. Monday, from 7:30 a.m.-5 p.m. Wednesday and from 6:30 a.m.-noon Thursday.

Oversized loads will not be able to cross the bridge during those hours.