Replacement of Pedestrian Bridge at Seneca Creek Aqueduct

A red stone aqueduct spans a creek leading into a river, while the sun sets behind it.
The new pedestrian bridge spanning the Seneca Creek Aqueduct.

NPS | Joe Reed, Park Engineer

Mile 22.8: The Seneca Creek Aqueduct is open.

The park replaced the existing pedestrian bridge across the west arch of the historic Seneca Creek Aqueduct (mile 22.8) in Poolesville, Maryland. The previously existing 1970s era bridge reached the end of its service life.

The project's aim was to increase visitor safety along the towpath, protect historic features of the park, and establish a more sustainable method of crossing the west arch of the Seneca Creek Aqueduct that failed during a flood in September 1971.

The project was focused on the replacement of the previously existing bridge. No repairs to the historic aqueduct were done as part of this effort.

 
 
A wood and metal pedestrian bridge spans a portion of a stone aqueduct.
The newly placed pedestrian bridge at the Seneca Creek Aqueduct

NPS | Joe Reed, Park Engineer

NO CURRENT DETOURS AND CLOSURES

The Seneca Creek Aqueduct at mile 22.8 is OPEN..

FREQUENTLY ASKED QUESTIONS (FAQs)

What is the need for the project?

The west arch of the Seneca Creek Aqueduct failed during a flood event in September 1971. The arch failure has been stabilized by the National Park Service (NPS) but never restored. A timber pedestrian bridge was installed shortly after the failure in the 1970s to bridge across the west arch. This bridge has experienced significant weathering and deterioration over the years, and it has reached the end of its service life. The bridge needs to be replaced to prevent any further deterioration and to ensure visitor safety at the Seneca Creek Aqueduct crossing.

What does the project include?

The project consists of removing the existing timber pedestrian bridge and its associated support materials, installing a pre-cast concrete abutment on the upstream side of the aqueduct, and placing the new Fiber Reinforced Polymer (FRP) composite pedestrian bridge. The concrete abutment on the upstream side will be offset away from the historic masonry in order to protect it. The National Park Service (NPS) anticipates the contractor to rely on a crane set up in the Rileys Lock parking lot to perform the work.

 
Existing timber pedestrian bridge spanning the failed west arch of the Seneca Creek Aqueduct.
The previously existing timber pedestrian bridge spanning the failed west arch of the Seneca Creek Aqueduct. This bridge has been replaced with a new pedestrian bridge.

NPS | Joe Reed, Park Engineer

Where will the project take place?

This project took place at the Seneca Creek Aqueduct on the C&O Canal towpath at mile 22.8, approximately 8 miles downstream of Lock 25 – Edwards Ferry, and 0.7 miles upstream from Lock 23 – Violettes Lock.

When will the project begin and end?

The project began in late November 2021, and the aqueduct was re-opened in February 2022.

How will this project benefit park visitors?

With the project complete, the method of crossing the failed arch of the Seneca Creek Aqueduct is safer and more sustainable for visitors.

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. Permits authorizing the work from other regulating agencies (e.g. Maryland Department of the Environment) have also been issued.

What is the park doing to protect those resources during the project?

NPS resource protection experts, engineers, and the contractor’s team have surveyed the adjacent historic features at the project site. The new bridge has been placed so that the new, precast abutment on the west (upstream) side is offset away from the historic masonry. NPS representatives monitored construction activities, along with the contractor’ operations and visitor safety during the project with the goal of safely protecting the environment surrounding the project. Every project undertaken by the NPS is conducted in compliance with the National Environmental Protection Act (NEPA), the National Historic Preservation Act (NHPA), and other regulations.

How is the project funded?

The contract for the removal of the existing pedestrian bridge and installation of the new FRP bridge at the Seneca Creek Aqueduct in Poolesville, MD was funded from the National Park Service’s Repair Rehabilitation Program.

Who can I contact if I have further questions regarding the project?

Additional questions are to be directed to the park headquarters Monday-Friday at (240) 520-3135 and Saturday-Sunday and holidays at (301) 767-3714, or choh_information@nps.gov until our main phoneline service is restored.

 
A stone aqueduct spans a creek on a sunny, clear day.
View of the Seneca Creek Aqueduct over Seneca Creek featuring the newly placed pedestrian bridge spanning the failed west arch.

NPS | Joe Reed, Park Engineer

Last updated: February 10, 2022

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