Emsworth Lock and Dam, Back Channel Left Abutment Stabilization and Scour Protection

Emsworth Locks and Dams are located on the Ohio River immediately downstream from the city of Pittsburgh, Pennsylvania. The back channel dam and locks are located on Neville Island, Pennsylvania, at river mi 6.4. The dam length is 960 ft (293 m) and the water depth exceeds 30 ft.

During low-flow conditions the loss of the pools of the Ohio, Monongahela and Allegany Rivers, at the point of Pittsburgh, would cease all navigation. Shippers using Emsworth had estimated that loss of the dam would increase transportation costs by $130 million annually.

The $32 million U.S. Army Corps of Engineer’s Contract W911WN08B0007 was awarded to Trumbull Construction in July of 2008. Synthetex was brought into the project, working closely with the U.S. Army Corps of Engineers and Bergmann Associates for the design of formworks for the underwater casting of armor units for the scour aprons on both the Main and Back Channels of the Emsworth Locks and Dams. The concrete armor units ranged in sizes up to 32 ft x 18 ft x 6 ft and weights in excess of 15000 lb each. Prior to the installation of the HYDROCAST® Concrete Bag Scour Protection downstream of the dam, there were 10 ft (3.0 m) deep scour holes and 65% of the existing stone scour protection was in a failed state. Due to the extreme corroded state of the dam gates, failure of any one of seven lift gates would most likely cause a portion of the stilling basin to fail and possibly undermine the dam. The dam had been categorized as Dam Safety Action Class 1, urgent and compelling.

The scour protection measures consisted of grading, placing bedding stone, and installing HYDROTEX® concrete-filled bags downstream of the existing dam for six individual bays.  During the project, approximately 10000 yd³ (7600 m³) of concrete was placed in more than 200 individual armor units with no lost time for more than three years.