LOCK AND DAM NO. 25 SCOUR PROTECTION & REHABILITATION

Winfield, Missouri

Massman was asked by the U.S. Army Corps of Engineers to correct a problem that had resulted in significant scour occurring on the upstream side of Lock and Dam 25. At five of the piers, steel forms were pre-assembled on barges and then lowered into position, where they were attached under the pier footings by divers. The average water depth at the time of the installations was 37 feet with zero visibility. Divers used mechanical wedge anchors, pneumatic equipment, and hydraulic equipment to attach the forms to the existing concrete.

After the stay-in-place forms were installed under the dam piers, a sand and grout slurry was pumped underwater and into the forms. The slurry flowed evenly under the pier and around the existing wood foundation piling, filling in the scour areas. A grout cap was pumped on top of the slurry to interface with the bottom of the concrete footings. The sand/grout slurry and the grout were all stored, mixed, and pumped from work barges positioned on the upstream side of the dam.

Eight of the 17 dam tainter gates were repaired on-site. The bottom seals of the damaged gates were retrofitted and improved in order for the gates to seal properly. This work was crucial to reducing the underwater current immediately upstream of the dam, which was required for the safety of the divers.