Mississippi deltas rise at St. Louis
One of the most challenging tasks in constructing the new Mississippi River Bridge between St. Louis and southwestern Illinois was casting the massive concrete foundations for the towers.
Each of the two tower footings is 24 ft deep, 55 ft wide and 88 ft long. They are the largest of the mass concrete objects on the project. The tower bases sit on top of the footings and rise 70 ft above to the base of the bridge deck. Each massive foundation contains more than 1.9 million lb of closely packed reinforcing steel. The reinforcing steel was nicknamed the “canary cage” by some workers, who joked that even a canary could not fit between the bars.
Pouring the concrete for the first foundation, on the Illinois side of the river, took 43 hours and involved more than 3,600 cu yd of concrete.
Below the two foundations are six 12-ft-diam. drilled shafts sunk through about 30 ft of water, 70 ft of silt and mud and 20 ft of limestone.
The delta-shaped towers for the new Mississippi River Bridge reached their full 400-ft height over the summer. The bridge as a whole reached No. 4 on the ROADS & BRIDGES Top 10 Bridges list.
The bridge is the first bridge built in more than 40 years between downtown St. Louis and southwestern Illinois. The new bridge will carry the rerouted I-70 across the Mississippi River and give drivers less congestion and less travel delay than they have been experiencing with I-70 sharing the Poplar Street Bridge with I-55, I-64 and U.S. Rte. 40. The cable-stayed main span of the bridge will be 1,500 ft long, with a total span of 2,803 ft.
The deck segments and stay cables will be assembled at the same time in balanced-cantilever method.
Construction of the four-lane deck for the bridge has started and workers are connecting the first of more than 600 miles of cable between the towers and the roadway.
Construction work for the Illinois approach is proceeding well. Crews have completed installation of all the girders on the Illinois approach and have started the initial work to form up the driving surface. The Missouri approach structure is complete.
Live pictures of the construction site are available on the project’s website at www?.newriverbridge.org.
Construction of the bridge is part of the larger project of rerouting I-70, which also involves constructing a roadway connection between the existing I-70 on the Missouri side of the river and the new bridge, a roadway connection between the new bridge and the existing I-55/64/70 Tri-Level Interchange in Illinois and improvements at the I-55/64/70 Tri-Level Interchange. R&B