In June 2022, unprecedented amounts of rainfall caused substantial flooding, rockslides, and mudslides within Yellowstone National Park. Historic water levels caused severe damage to roads, water and wastewater systems, power lines, and other critical park infrastructure. (Video includes natural sounds only: no narration.)
On the morning of June 13, 2022, Yellowstone experienced a 500-year flood event. Northern parts of the park received a combined 7.5-9.5 inches of rain and snowmelt in a 24-hour period. The flood destroyed several sections of the North Entrance Road between Mammoth Hot Springs, Wyoming, and Gardiner, Montana, and three sections of the Northeast Entrance Road between Lamar Valley and Cooke City/Silver Gate, Montana.
The park immediately set a range of life and safety objectives to ensure all employees and visitors were safe and accounted for, restore power, divert damaged wastewater systems, and help local communities with emergency response. Within 36 hours of the event, the park evacuated all visitors in developed areas and conducted initial damage assessments. Within 48 hours, the park restored power, diverted severed wastewater lines, and planned for recovery and resumption of operations when and where possible. The south loop of the park reopened on June 22, 2022, nine days after the flood event. As repairs continued, additional sections of road and backcountry trails opened throughout the summer.
6/14/22, Conducted initial damage assessments by resident Federal Highway Administration (FHWA) engineers.
6/14/22, Provided $10 million in Emergency Relief Federally Owned Roads - Quick Release (ERFO-QR) funding.
6/15/22, Started to improve Temporary North Entrance Road (Old Gardiner Road) with National Park Service (NPS) roads crews.
6/17/22, Provided additional $50 million in ERFO-QR funding.
6/17/22, Started planning and design for long-term reconstruction strategy.
6/21/22, Started temporary solution assessments to repair Northeast Entrance Road to Cooke City, Montana.
6/29/22, Hosted senior officials from congressional committees, NPS, and FHWA visit to develop strategies around short- and long-term recovery efforts.
7/1/22, Finished NPS improvements to Temporary North Entrance Road allowing for one-way employee traffic.
7/5/22, Started work on Temporary North Entrance Road after Diverting HK Contractors, INC from Old-Faithful-to-West-Thumb project.
7/11/22, Finalized temporary Temporary North Entrance Road designs and awarded contract to HK Contractors, INC.
7/26/22, Finalized temporary Northeast Entrance Road designs and awarded contract to Oftedal Construction, INC.
8/8/22, Started work on Northeast Entrance Road repairs by Oftedal Construction, INC.
10/15/22, Opened Northeast Entrance Road to the public.
10/30/22, Opened Temporary North Entrance Road to the public.
7/1/23, Reopened the Mammoth Hot Springs Hotel and Cabins after Mammoth wastewater system repairs.
Mammoth Wastewater System
A sewer line adjacent to the road that carried wastewater from Mammoth Hot Springs to a sewage treatment plant in Gardiner ruptured. Staff quickly rerouted the wastewater into percolator ponds used between the 1930s and 1960s, allowing for summer day-use visitors and residents to stay in the area. A new wastewater treatment system is being built to serve the Mammoth area with an anticipated summer 2023 completion.
Temporary North Entrance Road
Temporary North Entrance Road: June 16, 2022
Temporary North Entrance Road: October 24, 2022
High water during the flood event destroyed the North Entrance Road in several places, which cut off access to Yellowstone via the North Entrance in Gardiner, Montana. This road and the North Entrance are open year-round and serve as the only winter vehicle access in and out of the park. Two days after the flood, National Park Service (NPS) crews began hauling and applying 20,000+ tons of gravel to establish a passable one-lane along an historic dirt road. Constructed in 1879, the Old Gardiner Road was the original entrance road to Yellowstone until it was replaced in 1884.
On June 24, 2022, compliance to improve the Old Gardiner Road was completed, a contract was awarded to HK Contractors, INC, and work began on July 5. The estimated (to-date) cost of the project is $21 million. HK team’s substantial improvements to the road include: 1) widened 4 miles of road to a 22-foot minimum width by excavating 75,000 cubic yards of material; hauling 31,000 tons of road base, 14,500 tons of asphalt and 6,000 cubic yards of riprap; 2) installed 4,700 ft of guardrail and 22 culverts; 3) constructed mechanically-stabilized earth walls with materials including 12,300 square feet of welded-wire facing and a combined 9,000 cubic yards of select granular backfill and cobble rock facing; and 4) installed a pinned mesh wall with 632 soil nails ranging from 10-40 feet in length.
The effort to design and construct this road on an accelerated timeline was a direct result of the partnerships between NPS, FHWA Western Federal Lands Highway Division, RockSol Consulting Group, Inc., and HK Contractors, INC. The NPS is working closely with FHWA to evaluate a range of permanent road alignment alternatives and identify the most cost effective, resilient, and least environmentally impacting option.
Northeast Entrance Road: October 15, 2022
High water during the flood event destroyed the Northeast Entrance Road in three places and threatened lane collapse in two additional places. The Northeast Entrance Road is open to visitor vehicle traffic year-round and provides winter access to the communities of Cooke City/Silver Gate in Montana and to Lamar Valley, a main attraction in the park.
On July 26, 2022, a contract was awarded to Oftedal Construction, INC. and work began on August 8, 2022. Jacobs Engineering Group worked on design while Oftedal teams completed repairs. At a project (to-date) cost estimate of $25 million, Oftedal teams 1) stabilized over-steepened banks; 2) constructed coffer dams to re-route Soda Butte Creek in three places and Pebble Creek in two places; 3) removed 75,000 cubic yards of material from the Trout Lake Trailhead slope; 4) blasted rock to create a work area of 7,000 square feet above the work zones in Lamar Canyon and Trout Lake washouts; and 5) placed 11,000 cubic yards of riprap to armor the banks of the new road repairs.
The team of FHWA, Jacobs Engineering Group, Oftedal Construction, INC and NPS achieved an accelerated reopening date and the road opened to public travel on October 15, 2022. The NPS will work closely with the other team members as additional efforts continue in the spring of 2023 to finalize road sections in Lamar River Canyon and near the Trout Lake Trailhead.