Walking on Water: Drilling for Missisippi River Bridge Promising So Far

Geotechnical engineers are taking core samples of the bedrock where designers hope to put the foundations for the new Mississippi River Bridge. Randy Hitt, Mississippi River Bridge deputy project director for the Missouri Department of Transportation (MoDOT), said that so far the core samples seem to consist of good, solid rock.

Hitt said engineers will use information obtained from the geotechnical survey to design the foundations for the two piers that will support the bridge. They will decide, for example, whether they have to drill a shaft into the bedrock to support the piers or if they can use caissons, which rest on top of the bedrock.

In order to minimize obstruction to barge traffic, the new bridge will have a clear span of 1,500 feet between the two foundations – the longest clear span across the Mississippi River in Missouri, Hitt said. In comparison, the clear spans of the Alton and Quincy bridges are about 800 feet and the clear span of the Cape Girardeau bridge is 1,150 feet, he said. Engineers think the two towers to support the cables that will hold up the bridge will have to be about 400 feet tall to support that long of a clear span, he said.

The new Mississippi River Bridge will touch down in Missouri just to the left (south) of the cement silos in the background. The cement silos belong to Continental Cement Co.

The geotechnical team assessing the bedrock includes people from HNTB, TSI, and Geotechnology Inc. Massman Construction provided the barge that served as a drilling platform. Geotechnology provided the drilling rig.

In 2001, Illinois and Missouri received approval for a new Mississippi River Bridge and associated roadways (shown on a map which can be viewed through this link) . The components of the project are:

• Relocated I-70 in Illinois, north of its current location

• A new, 8-lane, I-70 Mississippi River Bridge (revised from the original to four lanes)

• An interchange in Missouri with existing I-70 near Cass Avenue

• An improved I-55/64/70 Tri-Level Interchange in East St. Louis

• A connection between the existing I-55/64/70 Interchange and the relocation of I-70 called the I-64 Connector

• Improvements to ramps at the west side of the existing I-55/64/70 Poplar Street Bridge in Missouri

The two states lacked sufficient funding to construct all components of the project at the same time. The estimated cost of the Ultimate Project Concept is between $1.8 billion and $2.2 billion. The scope of work announced on February 28, 2008 is the first phase of the project. This phase is operationally independent since it can be funded and built to function as a viable transportation facility. See the Proposed Initial Phase for details.

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