Norrell Lock Chamber Bulkhead Stoplog Cutting
Mainstream was awarded the contract to provide commercial diving services for modifications to the main lock chamber at the Norrell Lock and Dam. As a part of the contract, new recesses and improved sill support would be installed to allow for the use of a new 110' wide stoplog system for lock dewatering.
Five-person dive teams removed sediment and debris by hand and diver-directed dredging, performed underwater surveys, and performed concrete demolition of the existing corbels. The corbels were demolished using hydraulic drills, breakers, and wire saws. Divers also assisted with the cofferbox placement and sealing, allowing the stoplog slots to be cut, removed, and installed in the dry by the Prime Contractor.
As progress was made on the project, the dive crew assisted with a variety of other tasks including underwater concrete forming, pouring, and finishing for new stoplog sill supports and closure of the center post sockets used for the previous stoplog system. Tasks included placing drill templates, drilling epoxy anchor dowels into the existing concrete, and installing rebar cages. Divers set both precast and plate forms, securing them with steel tiebacks, then placed concrete inside the forms using a tremie pipe.
The crews worked in litte-to-no visibility water on a scheduled rotation to manage a balance between lock closures for construction activities and allowing routine river navigation traffic to pass through the lock. Working from summer through winter meant temperature swings from 100+ degree heat index to single-digit wind chills.