RESTORATION AND REHABILITATION OF THE BIG SLACKWATER SECTION OF THE HISTORIC C&O CANAL ALONG THE POTOMAC RIVER

Prior to becoming a National Park, the Chesapeake & Ohio Canal was part of a network of American canals dug during the late 18th and early 19^th centuries for commercial trade. By the time it of its completion, canals had become an antiquated mode of transportation and the tow-path was later repurposed for recreation. In the project area, the tow-path is bounded by the Potomac River on one side and limestone cliffs along the other. In this segment, the path was originally constructed on fill sections behind masonry walls or on intermittent rock ledges. Annual floods caused damage and erosion to the tow-path which required the closure of several miles, forcing the use of unsafe detours along public roads. The project goal was to restore the path over a 1.5-mile stretch and included the construction of elevated walkways requiring 122 pier locations secured by over 800 rock anchors placed in the massive karstic limestone unit. The value-engineered project included investigation, design, and construction observation phases, and the analysis determined that simple spread footing foundations stabilized with rock anchors would provide adequate capacity, allow construction from barges, and were flexible enough to account for unexpected karstic features in the highly variable bedrock topography. To supplement the limited pre-existing subsurface data, a geophysical investigation that included SASW and electrical resistivity profiles were conducted. Project challenges including the application of geophysical surveys, construction from barges, and complications with anchor installation will be discussed.