Marine USCOE Soo Cofferdams

PREPARING FOR THE NEW SOO LOCK

The USCOE – Detroit District & Sault Saint Marie City Area Office constructed 2 – 90 ft diameter cofferdams in preparation of the new lock project.  

INSIDE THE PROJECT

The 2 cofferdams were designed to allow the Sabin Lock to be dewatered and for demolition of that lock to begin.  To construct the cells, we designed, fabricated, and install a 89 ft diameter double row template to assist with our construction.  The template allowed for the sheets to be on the outside because it was to fit tightly between the north and south lock faces.  At each tangent pint against the locks, a concrete seal pour was installed to prevent water from bypassing the structure.  

A large crane with extra boom was used to install the 172 sheets, which made up each cell.  Each sheet was set and threaded to its adjacent sheet creating an enclosed cell.  When all the sheets were installed and tamped to top of rock, the cell was backfilled with clean stone.  After filling and finishing the first cell, the template was removed and reused for the second cell.  

Upon completion of both cells, a drilling subcontractor was employed to install a series of piezometers inside each cell.  

In the course of the contract there were several changes of conditions.  The largest was an existing concrete sill not shown on the drawings, which required demolition prior to constructing the westerly cell.  

WHY IT MATTERS

The cofferdams were the first step toward construction of the new “Super Lock”, which will be the same size as the existing Poe Lock.  

BEYOND THE PROJECT

The construction of the new “Super Lock” will be vital infrastructure for the shipping industry for decades to come.