Polychrome Area Plan

 

October 21, 2024 Update: The construction season has come to an end and the Pretty Rocks bridge contractors have demobilized for the winter. In 2024, they successfully completed all the major excavation work, installed the east and west bridge abutments, and began assembling the bridge structure on the launch platform. That means we are still on track for a midsummer 2026 project completion, which will allow NPS to use the remainder of that season to work on any necessary repairs to the western half of the Park Road and take care of deferred maintenance of our west district facilities. We expect the full length of the road to be open and all bus services to resume in 2027. Until then, visitors can still take a transit or tour bus out to the East Fork area at Mile 43 between May 20^th and mid-September. Anyone traveling along the Park Road next summer should expect to encounter some construction traffic.

Look back through the Pretty Rocks Construction blog for photos and details on past progress. Check back in the spring, when construction resumes, and continue to look for blog updates throughout next summer.

 

Since late August 2021, a portion of the Denali Park Road near Polychrome has been displaced by the Pretty Rocks Landslide (mile 45.4), cutting off vehicular access to popular visitor destinations and facilities including Polychrome Overlook, Toklat, Eielson Visitor Center, Wonder Lake, and Kantishna.

Check the current conditions of the Park Road and visitor services.

Read more about the science and monitoring of the Pretty Rocks Landslide and other geologic hazards.

 

Contractors visit the Pretty Rocks site in spring 2023, looking east.

NPS Photo

 

Staff visit the Pretty Rocks site in summer 2022, looking west.

NPS Photo

Project Overview

The Federal Highways Administration (FHWA), in collaboration with the National Park Service (NPS), developed the Polychrome Area Improvements plan to restore reliable road access west of Pretty Rocks. The plan addresses several geologic hazards in the Polychrome area (Mile 44–46) that threaten public safety and infrastructure, and includes the construction of a bridge to span the Pretty Rocks Landslide. Funding for the bridge was secured through a combination of Bipartisan Infrastructure Law dollars, additional Federal Lands Transportation Fund dollars, and 2023 Disaster Relief Supplement funding. The construction contract was awarded in January 2023 and work began in Summer 2023. Due to the road closure, buses will continue to travel no farther than mile 43 of the 92-mile Park Road and access to Kantishna inholdings will be primarily by air until the bridge is completed.

 

Rendering of Pretty Rocks project site (mile 45.4), with a school bus included for scale. Tan areas represent excavation. Not based on final designs and subject to change.

Source: BGC and Jacobs Engineering

Project Includes:

• Construction of a 475-foot long, 50-foot tall, and 24-foot wide steel truss bridge to span the Pretty Rocks Landslide.
• Excavation to the east and west of the bridge to accommodate construction activities and traffic. The majority of the excavated material will be placed on the slope below the road.
• Slight realignment of the road on the west side of the bridge to allow for a proper turning radius for buses and other vehicles getting on and off the bridge.
• Installation of 23 thermosyphons in the ground around the eastern abutment of the bridge to mitigate the potential for permafrost thaw and ensure the longevity of the bridge.
• Installation of a retaining wall on the uphill side of the road to the east of the bridge, a soil nail wall below the road near the east abutment, and rock dowels below the road near the west abutment to stabilize the slopes.
• Rock scaling, rock reinforcement, and/or creation of rockfall ditches to reduce rockfall risk.

 

Diagram not based on the final design and subject to change.

Source: NPS and Jacobs Engineering

 

NEPA and NHPA Compliance

The National Environmental Policy Act (NEPA) mandates an environmental assessment of any proposed federal action that has the potential to “significantly affect the quality of the human environment." Section 106 of the National Historic Preservation Act (NHPA) requires that federal agencies identify and assess the effects its actions may have on historic properties and consider public views and concerns about historic preservation issues when making final project decisions. Compliance with the NHPA is conducted concurrent with, but as a separate process to, the NEPA compliance process.

Environmental and cultural compliance for the Polychrome Area Improvements project was formally initiated in October 2021 and was completed in March 2022:

• Step 1. Conducted consultations and civic engagement (July–Oct ‘21)
• Step 2. Analyzed impacts and assessed the effect to historic properties (Oct–Nov ‘21)
• Step 3. Identified mitigations and prepared environmental document (Nov–Dec ‘21)
• Step 4. Posted environmental document for public review (Jan–Feb ‘22)
• Step 5. Reviewed public comments and prepared decision document (Feb ‘22)
• Step 6. Released final decision document to the public (March ‘22)

The NPS contracted an environmental consulting firm (AECOM) to prepare the Environmental Assessment (EA), which considered the environmental consequences of a “no action alternative” (no new bridge and the road remains closed) and an “action alternative” (construct Pretty Rocks Bridge and Polychrome Road Improvements).

Prior to the development of the EA, the NPS consulted with federally recognized Tribes, Alaska Native Corporations, State and local governments, and the State Historic Preservation Office. The NPS also hosted two virtual public meetings in October 2021 to identify and document specific concerns, issues, and potential impacts of both alternatives. Issue topics analyzed in the EA included geology, socioeconomics, visual resources, visitor use and experience, noise / soundscape, wildlife, wetlands and vegetation, cultural resources, and wilderness. Following the publication of the EA in January 2022, two additional virtual public meetings were held to discuss the analysis and provide information to aid the public in reviewing and commenting on the compliance document.

After careful consideration of resource impacts, consultation with stakeholders, and review of public comments, the NPS concluded that the Polychrome Area Improvements project would not have a significant effect on the environment. The Finding of No Significant Impact (FONSI) was approved by the NPS Alaska Regional Director and released to the public in March 2022.

 

How Can I Get Involved?

Learn about other plans and become familiar with the Denali Planning Portfolio.

Check the NPS Planning, Environment, and Public Comment (PEPC) website for documents available for review and comment.

If you have questions, please email us.