Alaska's Largest Fish Passage Culvert Frees Tyonek Creek
Revitalizing Infrastructure for People, Salmon

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If you’re standing in Anchorage, Alaska, you can see a culturally important landmark and place in the distance: the so-called Sleeping Lady. Her other names are Dghelisha (in Dena’ina) and Susitna (in English, and likely adapted from the Dena’ina word “Suyitnu” meaning “Sand River” in reference to the glacial waters that flows just east). Just south, and across Cook Inlet, is the Native Village of Tyonek. Your naked eye will only see the Alaska Range and hazy lowlands that meet the sea, but you can be landing in Tyonek in as few as 21 minutes after taking off from Merrill Field in a very small plane. 

Along the way, the landscape below very quickly changes from urban city to pothole lakes rich with waterfowl, wild snaking creeks and huge braided rivers full of fish. To your left, gray, silt-laden marine waters where the occasional beluga whale or oil platform breaks the surface. Once you fly low over the Susitna River and pass Sleeping Lady, you’ll hug the northwestern shoreline of Cook Inlet until you descend and land on Tyonek's small, gravel runway. Upon landing, you'll be greeted by people on ATVs and in trucks collecting the mail or perhaps picking up a relative who's back from a doctor's visit in Anchorage or returning with an ice cream cake for their kid's birthday party. 

A small plane lands at Tyonek Airport.

Despite this close proximity to Alaska’s biggest city, the logistics of getting to Tyonek—including materials and supplies—are challenging. Small plane or boat are your options (weather dependent) and, for the Tebughna People (Dena’ina for “beach people”), food security is a priority. Tyonek and partners have been investing in cost-effective, safe, and fish-friendly infrastructure that lets an important food source—salmon—get where they need to go. This helps continue a long tradition of fishing and caring for the land. 

Revitalizing Infrastructure for People, Salmon

Tyonek Timber Road. Logging Road. Names speak to history, but these speak to recent times. Tyonek’s history stretches way beyond roads that came with the exploration of the Cook Inlet region by oil and gas companies in the 1950s and 1960s and logging that came in the 1970s. 

Tyonek Timber Road where it intersects Tyonek Creek at the coast of Cook Inlet.

The Native Village of Tyonek and Tyonek Native Corporation steward a large land base with extensive intersections of salmon streams and roads—134 miles of roads to be exact. And where roads cross streams and rivers, they need culverts or bridges. 

A number of these road-stream crossings are located on “flashy” river systems that rise and fall quickly during or after storms and have a history of washing out roads with undersized culverts on an annual basis. Due to Tyonek only being accessible by air or barge, infrastructure installation and repair costs are very high. In addition to chronic road washouts delaying tribal subsistence and land use practices, more than 30 of Tyonek’s road-stream crossings were documented as barriers for juvenile salmon. Luckily, these critical pieces of infrastructure can be designed with dual intentionality of maintaining reliable road infrastructure and keeping migratory corridors open for fish and free-flowing rivers. 

In 2012, the Tyonek Tribal Conservation District began working with partners to install bigger, channel-spanning stream simulation culverts designed to reduce road maintenance, safely carry flood flows, provide for fish passage fish passage
Fish passage is the ability of fish or other aquatic species to move freely throughout their life to find food, reproduce, and complete their natural migration cycles. Millions of barriers to fish passage across the country are fragmenting habitat and leading to species declines. The U.S. Fish and Wildlife Service's National Fish Passage Program is working to reconnect watersheds to benefit both wildlife and people.

Learn more about fish passage
, and support natural stream processes along the Tyonek road system. These superior culverts have been demonstrably better for fish and have held fast during major flood events. The culvert that spans lower Tyonek Creek marks the partnership’s 13th fish and flood-friendly culvert. Salmon seeking the 30 miles of habitat upstream could be seen moving upstream under Tyonek Timber Road immediately after the culvert was installed. If fish could talk, we know what they’d be saying: bigger is better. And at over 45 feet wide, 22 feet tall, 120 feet long, this is Alaska's biggest fish passage culvert. 

The new culvert overlaid with its design schematic and the approximate location and size of the old, too-small culvert. 

By the Numbers

Old Culvert

New Culvert

6 feet wide45 feet 10 inches wide
5 feet high22 feet high
99 feet long120 feet long
good for nothinggood for salmon, people, and the land
Old culvert (left), new culvert (right). 

Why bury such a large corrugated structure structure
Something temporarily or permanently constructed, built, or placed; and constructed of natural or manufactured parts including, but not limited to, a building, shed, cabin, porch, bridge, walkway, stair steps, sign, landing, platform, dock, rack, fence, telecommunication device, antennae, fish cleaning table, satellite dish/mount, or well head.

Learn more about structure
rather than erect a traditional bridge? With a span large enough to house the plane you flew in on, the structure is technically considered a “buried bridge” and is seconded in Alaska only to the replacement for the Captain Willian Henry Moore bridge outside Skagway (designed with earthquakes in mind). The Tyonek structure designed with fish in mind consists of a bottomless arch sitting on concrete foundations set well below the bottom of the creek. The arch, built out of 240 plates weighing 500 pounds each and held together by 1,416 bolts, allowed for in-place assembly of components that could be shipped on pallets and moved with forklifts. This modular approach and reduced the size of equipment and materials barge to Tyonek. Cost and logistics are huge players when it comes to infrastructure improvements in rural Alaska and this whale-of-a-culvert is a great example of creative engineering.

Partners help vegetate the banks of Tyonek Creek in the construction zone.

Celebrating the Return of Salmon & Momentum Forward

On September 27, 2024, community members, Tribal Leadership, landowners, school children, agency partners, contractors, and non-governmental organizations gathered for a culvert blessing ceremony in Tyonek to celebrate completion of this massive project and a decade-long, collaborative effort to remove all barriers to migrating salmon in the Tyonek Creek watershed. 

Ribbon cutting at the culvert blessing ceremony on September 27, 2024.
Fish passage-themed cupcakes at the celebration.

Removal of every fish passage barrier within the 6-million-acre Tyonek Tribal Conservation District is in sight, as is a larger goal of a barrier-free Alaska within our lifetimes. The U.S. Fish and Wildlife Service is dedicated to supporting Alaska communities and salmon habitat statewide. We are investing in Tribal capacity building and on-the-ground projects to connect fish habitats and human communities. In the near-term, this includes supporting the Chickaloon Village Tribal Council in pursuing a barrier-free Moose Creek, working throughout Southeast Alaska to inventory, prioritize and restore fish passage where roads and streams intersect, and removing barriers to fish in the Yukon and Kuskokwim watersheds. 

Conservation is a Team Sport

Partners include Tyonek Tribal Conservation District, Tyonek Native Corporation, Native Village of Tyonek, U.S. Fish & Wildlife Service, USDA Natural Resources Conservation Service, Alaska Department of Fish and Game, Alaska DNR Division of Forestry and Fire Protection, National Oceanic and Atmospheric Administration, Cook Inlet Region Inc., Boutet Company, HDR Inc., Tyonek Contractors LLC, Tyonek Hospitality, Western Construction, Knik Tribal Council, and Contech.

Funds involved: 

  • U.S. Fish and Wildlife Service ($2.4M in Bipartisan Infrastructure Law and National Fish Passage Program funds)
  • National Resources Conservation Service ($1.9M via Environmental Quality Incentives Program)
  • Cook Inlet Region, Inc. ($160,000 gravel donation)
  • State of Alaska Department of Forestry ($74,000)
  • Donations and other ($90,000)

In Alaska we are shared stewards of world renowned natural resources and our nation’s last true wild places. Our hope is that each generation has the opportunity to live with, live from, discover and enjoy the wildness of this awe-inspiring land and the people who love and depend on it. 

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Anadromous fish
Fish migration
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