NPS | Professional Services Division – C&O Canal National Historical Park The Great Falls Entrance Road (near milepost 14.3) is open. The Swains Lock parking area (near milepost 16.7) is open.
The existing timber retaining wall surrounding the Swains Lock parking area was also impacted by this event. This project will repair embankments, place drylaid stone “rockery” armoring walls, reconstruct roadway shoulders, install a new drainage pipe, and stabilize stream beds. These project areas serve as primary access points to some of the most highly used areas of the park. Maintaining these access routes is critical for safely supporting the over 1 million visitors that explore Great Falls, MD, each year. 
NPS | Professional Services Division – C&O Canal National Historical Park 
NPS | Professional Services Division – C&O Canal National Historical Park 
NPS | Professional Services Division – C&O Canal National Historical Park CURRENT DETOURS AND CLOSURESThe Great Falls Entrance Road (near milepost 14.3) is open. The Swains Lock parking area (near milepost 16.7) is open. Above are maps showing the project areas. Park users are asked to not enter any construction project areas and follow all flaggers and signage. FREQUENTLY ASKED QUESTIONS (FAQs)What is the need for the project?On July 8, 2019, a high intensity rainfall event caused damage to National Park Service (NPS) infrastructure along the Great Falls Entrance Road and at the Swains Lock parking area. Currently, there are existing eroded embankments that threaten to undermine the Great Falls Entrance Road and scoured roadway shoulders causing major drop-offs from the edge of the roadway. An existing damaged timber retaining wall along the edge of the Swains Lock parking area needs to be remediated. Without repairs, these systems will continue to degrade, impacting access along the existing roadway/parking area and potentially damaging historic features. What does the project include?This project will repair eroded embankments, place drylaid stone “rockery” armoring walls, reconstruct roadway shoulders, install a new drainage pipe, and stabilize stream beds. At the Swains Lock parking area, the existing timber retaining wall will be removed and replaced with an embankment constructed with fill and seeded topsoil. Traffic control will be provided to close one lane of the Great Falls Entrance Road intermittently during construction to facilitate the repairs. Where will the project take place?This project will take place along the Great Falls Entrance Road (near milepost 14.3) and Swains Lock parking area (near milepost 16.7) within the historic Chesapeake & Ohio Canal National Historical Park. This project is located in Potomac, MD. When will the project begin and end?The project is anticipated to begin Fall 2025 and continue through winter 2026, weather dependent. How will this project impact park visitors?During construction, the Great Falls Entrance Road will remain open with single lane closures intermittently. Visitors are asked to obey all signage and flagging operations. While single lane closures are in-effect, visitors may experience delays upon entering and exiting the Great Falls area. During construction, the Swains Lock parking area will be closed. The Canal Quarters at Lockhouse 21 will remain accessible throughout construction. The nearest upstream parking lot for towpath access is Pennyfield Lock (milepost 19.6) and the nearest downstream parking lot for towpath access is Great Falls (milepost 14.3).
How will this project benefit park visitors?The completion of this repair work will improve safety, reduce impacts of future storms, stabilize/preserve historic resources, and provide for reliable access to Great Falls and the towpath via Swains Lock. The work will make the park more resilient to flooding and climate associated hazards. Many existing impairments, such as erosion, shoulder drop-offs, and damaged infrastructure will be repaired to result in a safer visitor experience. How will this project impact natural and cultural resources?Every project the NPS executes undergoes review by a multidisciplinary team to ensure compliance with Section 106 of the National Historic Preservation Act (NHPA), National Environmental Policy Act (NEPA), and other federal, state, and local laws. What is the park doing to protect those resources during the project?NPS resource protection experts, engineers, and the contractor’s team will be monitoring the work, along with contractor’s operations and visitor safety during the project with the goal of safely protecting the environment surrounding the project. How is the project funded?This project is being funded through the Emergency Relief for Federally Owned Roads (ERFO) program under interagency agreement between National Park Service and Federal Highway Administration – Eastern Federal Lands. Who can I contact if I have further questions regarding the project?Additional questions are to be directed to the park headquarters at 301-739-4200. 
NPS | Professional Services Division – C&O Canal National Historical Park 
NPS | Professional Services Division – C&O Canal National Historical Park |
Last updated: July 15, 2025