Paw Paw Tunnel Scaling Project

A 2020 current conditions image shows a rock slide from April 2016 near the northern (downstream) entrance of the tunnel. The current scaling and repair project is one to prevent rock slides like this in the future and to remove debris from the canal prism.

NPS | Joe Reed, Park Engineer

The Paw Paw Tunnel is currently open. However, the towpath just downstream is closed.

Phase 2 of construction for the interim slope stabilization at the north (downstream) portal of the Paw Paw Tunnel was completed in July 2019. In September 2020, the National Park Service awarded a Design-Build contract to stabilize the rock slopes along an approximately 1000-LF length of canal just downstream (North) of the Paw Paw Tunnel, located in the Chesapeake & Ohio Canal National Historical Park in Alleghany County, Maryland.

While more recent projects completed in 2017 – 2019 addressed the stability of rock slopes on the towpath (East) side of the canal, the current project will address the highest risk slopes within the 1000-LF long reach of canal, on all sides. Loose rock above the towpath at the “cut” and north (downstream) portal presents potential safety hazards to visitors and cultural resources (i.e. Paw Paw Tunnel). The rock also threatens to damage the boardwalk section of the towpath. This stabilization project provides for visitor safety from rock fall as well as protection for the boardwalk/towpath and Paw Paw Tunnel Portals by removing existing debris remaining in the canal prism from a rockslide in May 2016, stabilizing the rock face adjacent to the canal, and replacing the wooden boardwalk that serves as the towpath for a portion of this stretch.

As of November 2020, the towpath North of the tunnel, near mile 155.1, has been closed and the Tunnel Bypass Trail detour activated. This closure is due to potentially unstable conditions observed in the rock mass during a recent site investigation. This detour is anticipated to remain in place until construction can be completed to mitigate the rock fall hazards. While design & permitting is still underway, construction is anticipated to extend until as late as mid-2022. During this time, NPS anticipates that the Paw Paw Tunnel will remain open to visitors. However, through-access onto the towpath downstream of the tunnel will be closed until the rock fall hazards are addressed through construction of the awarded contract.

Frequently Asked Questions

When will the project begin and end?

Construction for the interim slope stabilization at the north portal of the Paw Paw Tunnel began in June of 2017 and was completed in July 2019. The current design build contract, awarded in September 2020, will continue with addressing rockfall hazards and aim to remove rock and debris caused by the rockslide of 2016. This work will also address the timber boardwalk portion of the towpath by removing and replacing it. A design-build type of procurement facilitates the contractor’s team to complete the design/permitting, as well as construct the fix. Once the ongoing design is completed and permitted, construction is anticipated to begin in 2021 and extend into 2022.This work will provide long-term safe passage through this stretch of towpath. The National Park Service is doing everything possible to minimize closure time and impacts to visitors.

What is the need for the project?

Loose rock above the towpath at the “cut” and north portal (downstream entrance to the tunnel) presents potential safety hazards to visitors. The rock also threatens to damage the boardwalk section of the towpath. This project provides for visitor safety from rock fall as well as protection for the boardwalk/towpath.

What does the project include?

While the next phase is still in design, it is anticipated that the project will include measures similar to the previous two phases. Typical measures include “scaling,” or removing, loose and unstable rock and debris from above the towpath/boardwalk in the “cut” approaching the north portal. Additionally, rock was “pinned” in place to provide further stability and long-term protection. Rock scaling and pinning has occurred in this area before. Measures to better manage surface and ground water are also included. In some areas, a pinned mesh will be used to stabilize localized rock slopes. In some areas, existing “shelves” of rock will be supported through the use of concrete “shear keys” pinned underneath the rock slabs into competent rock. Concrete will be colored and sculpted to minimize aesthetic impacts to the landscape.

What is the history of the Paw Paw Tunnel?

The Paw Paw Tunnel is one of the most significant engineering features on the Canal. To save building six miles of canal along the river, the C&O Canal Company decided to construct a tunnel through a steep topographic ridge now called Tunnel Hill. When work began on the tunnel in 1836, the builders estimated the project would be complete within two years. The tunnel ultimately required 14 years to complete due to labor issues and violence, funding shortfalls, work stoppages, and the challenges of digging a 3,118-foot tunnel through the hard, loose shale. The tunnel opened in October 1850 with rockslides continuing to be a challenge throughout the tunnel’s history.

 

During the 2017-2019 project work, the rock wall along the towpath was bolted and pinned with rockfall mesh to prevent future rockslides.

NPS | Joe Reed, Park Engineer

How will this project benefit park visitors?

Visitor safety is improved by removing loose rock and debris from above the towpath and by stabilizing the remaining rock to reduce potential for future rock fall. This work also protects the boardwalk section of the towpath from potential rock fall.

A slide that occurred in 2016 deposited a large amount of rock debris into the canal, which stretches over to the boardwalk with additional areas of concern throughout the “cut” that have been identified by the design team. This material will be removed, and the slope will be stabilized to restore the canal.

How will this project impact natural and cultural resources?

Every project the National Park Service 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.

An environmental assessment (EA) was prepared by the park for phase 1 & 2, which can be found on Planning, Environment and Public Comment (PEPC) website. An assessmnent was also prepared for the project currently being designed, which can also be found on the PEPC website.

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

National Park Service resource protection experts, engineers, and the contractor’s team will be monitoring the stone and brickwork in the tunnel, along with contractor’s operations and visitor safety during the project with the goal of safely protecting this unique cultural resource and the environment surrounding the project. Every project undertaken by the National Park Service is conducted in compliance with the National Environmental Protection Act (NEPA), the National Historic Preservation Act (NHPA), and other regulations. Please see the Environmental Assessment (EA) prepared by the park for further details.

How will this impact park visitors?

To facilitate the work, construction equipment staging is anticipated to require closing a section of the Paw Paw Tunnel Campground Parking Lot. Additionally, temporary delays are expected as work crews and equipment move to/from the work site. As the design develops and construction work approaches, additional updates regarding detours, shuttle services, and other impacts to visitors will be provided by the NPS. While the tunnel currently remains OPEN, the section of towpath downstream (North) of the tunnel near mile marker 155.1 has been CLOSED due to the increased potential for rock slope instability.

How much does the project cost?

The first project (consisting of phase 1 and 2) was completed in 2017 – 2019 for a cost of less than $1 million and was funded by the National Park Service’s National Recreation Fee Program.

The design build contract for more extensive slope stabilization and boardwalk rehabilitation was awarded in September 2020 for $7.64 million and was funded from the National Park Service’s Line Item Construction Program.

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

Reach out to the park Headquarters at 301-739-4200.

 

A graph and map showing the Tunnel Bypass Trail and elevation change.

NPS | Andrew Landsman

Tunnel Bypass Trail

How long is the Tunnel Bypass Trail? How steep is it?

The Tunnel Bypass Trail is approximately a mile and a half in length with an elevation change of 375 feet. From the upstream (parking lot) end, the Tunnel Bypass Trail begins by crossing the canal prism and climbs 0.63 miles to the top (or about one foot of rise per nine feet of distance). On the downstream (construction) end, the bypass begins where the Tunnel Hill Trail meets the towpath near mile marker 155 and climbs 0.82 miles to the top (one foot of rise per 11.5 feet of distance).

What should I know about the Tunnel Bypass Trail?

Wear sturdy shoes that have good traction. Carry and drink lots of water during ascent and descent. Plan for the Tunnel Bypass Trail taking between one and a half to two and a half hours depending on your load, fitness level, and pace. Cyclists are reminded that they are required to dismount along the Tunnel Bypass Trail.