Building Drilled Shafts to Bridge the Mississippi-Paper

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Michels Corporation installed 242 permanently cased drilled shafts to support 28 piers for the new Interstate 74 twin-arch bridge connecting Moline, Illinois, and Bettendorf, Iowa. Most of the shafts—233—were built from barges in the Mississippi River, using up to four drill rigs. Crews installed 7- to 10-foot-diameter shafts, drilling rock sockets as deep as 28 feet and shafts to depths of about 60 feet.<br /><br />The river setting created major logistical and technical challenges. Tugboats coordinated the movement of crews, equipment, casing, reinforcement cages, excavated material, and concrete; some pours required transporting as many as five concrete trucks by barge. Strong currents, changing water levels, freezing conditions, and limited access complicated the work. At some locations, crews encountered bedrock caverns and developed solutions with the project engineer. A custom “Kitchen Sink” tool helped cut rock to position casing accurately where bedrock was exposed.<br /><br />A load test confirmed shaft capacity and allowed 24 rock sockets to be shortened by a combined 228 feet, reducing time and cost. Cross-hole sonic logging and concrete coring supported quality control, while some identified defects required pressure-grouting remediation. Michels also developed an approved plan to contain and treat drilling water, protecting the river and meeting environmental requirements.<br /><br />The project recorded 39,000 work hours without an OSHA-recordable incident. Despite weather delays and complex river operations, Michels completed its work six months ahead of the contractor’s schedule, helping advance construction of a major new Mississippi River crossing.

Keywords

Interstate 74 bridge

Michels Corporation

drilled shafts

Mississippi River

twin-arch bridge

rock sockets

barges

casing

quality control

OSHA-recordable incident