Hoonah, Petersburg, and Skagway Roadway and Culverts Project

Official Project Name: SKG-HNH-PSG Roadway & Culverts - DEC 20 SE PR
State Project No: 0093008 | Federal Project No: SFHWY00447
A project in the DOT&PF 2020 Storm Recovery Program

Project Overview

The Alaska Department of Transportation and Public Facilities (DOT&PF) is repairing several  sites damaged in the 2020 Storm in Hoonah, Petersburg, and Skagway, Alaska.

Purpose & Need

In December 2020, a week of record rainfall in Southeast Alaska led to widespread flooding and landslides in local communities. By the end of the storm, Alaska Department of Transportation and Public Facilities (DOT&PF) roads in Juneau, Haines, Skagway, Hoonah, and Petersburg had sustained widespread damage. DOT&PF conducted immediate emergency repairs on numerous sites to address roadway damage, washed out culverts, filled drainage ditches, and landslides. Permanent repairs are required to rebuild Alaska’s infrastructure.
The purpose of this project is to repair infrastructure that was damaged by the December 2020 Storm event.

Project Description

This project will repair damages includes emergency and temporary repairs at four locations between Hoonah, Petersburg, and Skagway that experienced damage from the storm event. Permanent repairs address damage affecting culvert replacement, paving, roadway and embankment reconstruction, rock scaling, and striping. Proposed typical sections generally match the existing road sections. There are no planned improvements to the road widths, grades, fore-slopes, ditches, or back-slopes at any locations included in this project. This project does not address damage and repairs on the Klondike Highway north of Skagway because that location has its own standalone project.
Hoonah: Front Street Mpt 0.20 Culverts
The repair at this location consists of replacing the two culverts that are plugged with storm debris and an associated inlet structure. The two culverts will be replaced with a single concrete box culvert due to cover restrictions, and the road subbase will be rebuilt. Both lanes of travel will be repaved, pavement markings will be reapplied, curb & gutter will be reinstalled, and the sidewalk will be rebuilt. Additional work includes scaling the rock slope and installing rock dowels above the culvert inlet to reduce the debris potential at the culvert inlet.
Petersburg: Mitkof Highway, Mpt 15.46 Culvert
Coordination with the Alaska Department of Fish & Game has confirmed that the replacement culvert must provide fish passage. The repair at this location consists of removing the damaged culvert and replacing it with a structure with an increased culvert diameter to provide fish passage and addition of concrete headwalls at the culvert inlet and outlet. Both lanes of travel will be rebuilt and repaved, and pavement markings will be reapplied.
Petersburg: Mitkof Highway, Mpt 2.57 Culvert
The repair at this location consists of removing the damaged inlet section of the culvert to the failed junction, along with the overlaying roadway subbase and pavement as needed. A new section of culvert will be attached to the existing intact culvert, and a headwall installed to protect the culvert inlet. Field investigation noted the repair of the culvert inlet as an eligible permanent repair and that a headwall at the inlet would represent a betterment which is not eligible for funding. The road subbase and pavement disturbed by the culvert inlet replacement will be rebuilt, and the eastern lane repaved and striped for 50-ft.
Skagway: Klondike Highway
This project will remove and replace a section of the existing 48-inch corrugated steel pipe at the culvert inlet and outlet, and perform permanent stabilization of the embankment, including excavation of existing material and replacement with an approximately 6-foot-deep structural roadway section, constructed of evenly spaced geogrid layers and selected material. As a result of the proposed embankment repairs, existing pavement and guardrail would be removed and replaced with new materials.
The lane and shoulder widths will match existing pre-storm dimensions. Grades, cross slopes, fore slopes, back slopes and ditches will match existing, where possible, with minor modifications expected to meet the standards. Minor changes to the existing grade are needed to provide smooth transitions and meet the required design standards. Locations where the project includes safety appurtenances, such as guardrail, will be improved. Replacement will include the replacement of old materials with new and be constructed according to current standards. Roadway striping will be restriped according to current standards and signs that have diminished reflectivity will be replaced.

Project History

Hoonah: Front Street Mpt 0.20 Culverts
Front Street is a rural major collector road serving the community of Hoonah with a 2022 AADT of 1,290 vehicles per day (VPD). This location features two side-by-side culverts that carry an unnamed drainage across Front Street at Mpt 0.20, adjacent to a fuel storage facility which is southeast of the ferry terminal. Prior to entering the twin culverts, the unnamed drainage flows down a rock face. Both existing culverts were damaged and blocked by debris from the rock face during the flood.

Petersburg: Mitkof Highway, Mpt 15.46 Culvert
Mitkof Highway is a rural major collector road serving Petersburg. This site is located on Mitkof Highway at Mpt 15.46, northwest of the Crystal Lake Hatchery. The 2022 AADT at Mpt 15.46 is 180 VPD as measured at the closest location, near Mile Post (MP) 16.46. The storm damaged the corrugated metal pipe at both ends and interior buckling due to flooding. The unnamed drainage is listed in the Anadromous Waters Catalogue as fish passage site 10203193, AWC Code 106-44-10170, and has documented observances of juvenile Coho (Silver) Salmon, juvenile Cutthroat Trout, and juvenile Dolly Varden. The existing culvert has a Fish Passage Rating of Red, indicating that it is inadequate for fish passage due to the culvert gradient and outfall height.

Petersburg Mitkof Highway, Mpt 2.57 Culvert
This site is located on Mitkof Highway at Mpt 2.57, across the street from the Alaska Marine Lines terminal in the City of Petersburg. The 2022 AADT is 1,110 VPD as measured at the closest location, near MP 3.45. An existing 36-inch corrugated high-density polyethylene (HDPE) culvert incurred damage at the inlet due to debris blockages. Clearing the debris blockage led to a pipe junction failing at the inlet section of pipe.

Skagway: Klondike Highway
Klondike Highway is a Rural Principal Arterial that begins in the City of Skagway and continues north to the Canadian border at Mpt 13.108. The design speed limit through the project area is 40 miles per hour (mph) and the current AADT is 440 VPD (measured in 2022).

The pre-disaster typical section at the project site includes two 12-foot paved driving lanes with a 2-foot-wide shoulder on the west side and a 4-foot-wide shoulder on the east side, with wood-post guardrail present on the east side.

Underground electric and communications utilities run along the west side of the roadway. There is a 48-inch corrugated steel pipe (CSP) culvert crossing the roadway at the site.

Findings from both the site visit in July of 2023 and survey of the site conducted in September of 2023 confirm that during the severe storm event of December 2020, the roadside ditches at Mpt 4.085 along the Klondike Highway became blocked by debris, which caused water and debris to backup and flow over the highway; resulting in damage to the 48-inch CSP culvert and saturation, failure, and subsidence of the roadway embankment. The culvert inlet and outlet are both damaged and partially crushed. Visible sagging of the highway surface and embankment was observed as well.

Status

The project is currently in design and nearing completion of the Environmental Document. Construction is anticipated to occur in 2027.

Temporary Traffic Disruptions

DOT&PF will coordinate with the local governments to develop a traffic control plan that minimizes impacts to residents and businesses, particularly during the tourist season, and safely guides and protects the traveling public in work zones.

Hoonah and Petersburg
The project will seek to keep one lane open throughout construction with the possible exception of short temporary closures for paving.  Nearby cruise ship terminal traffic in Hoonah will be maintained during daylight hours, with closures only permitted at night.

Skagway
Due to the nature of the highway repair, it is expected that both travel lanes will require closure during excavation and construction of the full width deep patch highway repair. Excavation and construction of the highway will occur overnight, during the time when the US/Canada border crossing is closed (11 pm to 7 am). Provisions will be made to safely move emergency vehicles through the project area during full closures. During daylight hours the highway will be reduced to single-lane traffic with flaggers. Lane restrictions will be conducted so that vehicles experience no more than a 10-minute accumulated delay or 40 vehicles are detained in a queue, whichever occurs first.