85 Years of Change: The Lower Guard Wall at Charleroi Locks and Dam

Abstract Only - The Monongahela River Locks and Dam No. 4 facility (commonly referred to as Charleroi Locks and Dam) is situated on the right (east) bank of the Monongahela River, approximately 20 miles south of Pittsburgh. Since its original construction by the US Army Corps of Engineers in the 1930’s the facility has undergone several major renovations, including the current work to increase the size of the dual lock chambers to accommodate modern barge and shipping traffic. These renovations have resulted in numerous different loading conditions that the original timber pile supported concrete structures were not designed to withstand, and which would have likely led to unsatisfactory performance or failure of the structures had they not been modified and reinforced accordingly.

This presentation will focus on a specific section of the facility’s lower guard wall, which has been subjected to significantly varying loading conditions over the past approximately 85 years. This includes the loads resulting from the lower guard wall previously functioning as a portion of a cofferdam system (for certain phases of the lock and dam renovation work) and currently acting as a portion of the dam across the Monongahela River. With limited original as-built drawings and other information to go by, complex and creative geotechnical and structural measures, including high capacity H-pile underpinning and inclined rock anchors installed underwater, were modeled, designed, and constructed in order to ensure the stability of the lower guard wall and continued operation of the lock and dam facility during the renovations.