Polychrome Area Plan

 

Updated: January, 2023

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.

The Federal Highways Administration (FHWA), in collaboration with the National Park Service (NPS), developed a plan to restore reliable road access west of Pretty Rocks by addressing several geologic hazards in the Polychrome area that threaten public safety and infrastructure. The plan includes constructing a bridge to span the Pretty Rocks Landslide, and design work is underway. The environmental and cultural compliance processes for the project were completed in March 2022. Funding was secured and a contract was awarded to begin construction in Summer 2023. Due to the road closure, buses will continue to travel no farther than mile 43 of the 92-mile Park Road until the bridge is complete, estimated for 2025.

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.

 
A mountainside of bare orange, yellow, brown, and gray rock. On the far side of the slope, a flat road is cut into the mountain, then suddenly drops away and piles of slumping rock can be seen below the road. Two people work with equipment on the rock.
Geotechnical investigations near the collapsed portion of the road at Pretty Rocks in summer 2022.

NPS Photo

 
a dirt road precariously situated on the side of a mountain
NPS road maintenance staff made an extraordinary effort in Spring 2021 to repair the road at Pretty Rocks. By August 2021, these road maintenance efforts were no longer sustainable in the face of the landslide’s accelerated movement.

NPS Photo

Project Overview

Although Pretty Rocks Landslide is the highest priority and will be addressed first, the NPS plans to take a comprehensive approach by implementing several engineered solutions along approximately two miles of the Denali Park Road (Mile 44–46) to ensure that once access is achieved through Pretty Rocks, it won't be subsequently jeopardized by another nearby hazard. The project is referred to as the “Polychrome Area Improvements” and has been separated into two phases to expedite the start date of the first phase and allow more time to secure funding and finalize designs for secondary phases:

 
A satellite image of the Polychrome area with colored lines overlaid to mark the boundaries of Phase I and Phase II project work.

Phase I

  • Construction of an approximately 400-foot steel 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 retaining walls and drainage improvements to the east of the bridge, on the uphill slope.
  • Rock scaling, rock reinforcement, and/or creation of rockfall ditches to reduce rockfall risk.

Phase II

  • Construction of a partially buried retaining wall and drainage improvements along 1,000 feet on the south side of the road above Bear Cave Landslide.
  • Temporary widening of the road above Bear Cave Landslide to accommodate traffic during construction.
  • Rock scaling, rock reinforcement, and/or creation of rockfall ditches to reduce rockfall risk.

Phase I will require approximately five months of excavation plus three months of bridge construction and will take approximately two years to complete. Road access through Polychrome is not anticipated during Phase I. Visitor transportation will be allowed to travel as far as mile 43 of the Park Road and buses will turn around at the East Fork Toklat bridge or the East Fork Cabin site. Access to Kantishna inholdings will be primarily by air until the bridge is completed.

Additional funding is needed to complete Phase II and it will be implemented at a later date. Road access through Polychrome is anticipated during Phase II, likely with some delays or temporary restrictions expected at the construction sites. Visitor transportation to destination points west of Pretty Rocks and regular traffic to Kantishna inholdings will be allowed during Phase II.

 

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.

 

Last updated: January 12, 2023

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Mailing Address:

PO Box 9
Denali Park , AK 99755

Phone:

907 683-9532
A ranger is available 9 am to 4 pm daily (except on major holidays). If you reach the voicemail, please leave a message and we'll call you back as soon as we finish with the previous caller.

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