Photo Credit: Yukon River Inter-Tribal Fish Commission
Part 3 [1]: The Cost of Fish Friendly Culverts
April 2026 – Gale K. Vick [2]
They cost what????
When I first started learning about culvert issues for fish passage, I had no idea what a rabbit hole I was entering. As mentioned in Part 2 of this series, not only are culverts extremely instrumental to anadromous fish passage, but they cost a heck of a lot of money to construct or replace. Think up to a million dollars or much more for a single pipe, with “fish friendly” pipes being the most expensive. And that cost is compounded by a minimal semi-annual inspection and maintenance.
According to the US Army Corps of Engineers / Hydrologic Engineering Center / River Analysis System [3]: “A culvert is a relatively short length of closed conduit, which connects two open channel segments or bodies of water. Two of the most common types of culverts are: circular pipe culverts, which are circular in cross section, and box culverts, which are rectangular in cross section.”
Within that simple explanation is a vast array of culvert designs, sizes, uses and maintenance requirements. And so many questions, starting with what is a “fish friendly” culvert? Just how big or wide do they need to be? And what do they need to be constructed from? Each culvert need is specific to geographical circumstances with remote site construction being an additional variable.
The current cost estimates for culverts and bridges on the Ambler Road alternatives are based on other project analyses and very likely not even close to reaching what the true costs should be. Right now, the state of Alaska already has thousands of culverts that need to be replaced, a situation that is contributing to salmon decline. The Ambler Road will substantially magnify that situation.
Realistically, how much does a single “fish-friendly” culvert cost? Examples of recent culvert replacement projects in Alaska:
- On the Parks Highway Fish Passage Improvement Plan [4] a single culvert replacement and reconstruction ranges from $1.1 million to $9 million.
- $4.6 million for replacement of a culverts in Tyonak to make fish friendly [5], including creating Alaska’s largest culvert (45’10” wide, 22’ high) [6]
- Naknek River Watershed culvert replacement $3.747million [7]
Ambler road project construction estimates currently run $765 million to over $2 billion [8] but that seems woefully inadequate based on the number of needed culverts. With over 3,000 -4400 currently estimated culverts needed for the Ambler Road, the implications for fish passage is enormous. Estimates in the March 2020 Final Ambler Road Environmental Impact Statement (EIS) [9], the 2024 Draft Supplemental (SEIS) and the hundreds of documents required for permitting, right-of-way agreements, etc., for the project are going to need massive cross-referencing and updating to provide any assurances at all that the Ambler Road can protect salmon, sheefish and other anadromous species. So far, judging from the projections, just the proposed size of culverts alone are a giant red flag.
Ambler Road Estimated Culverts [10] Final Supplemental Environmental Impact Statement (SEIS):
Number of minor culverts (to 3 feet wide)
- Alternative A: 2,864
- Alternative B: 3,150
- Alternative C: 4,076
Number of moderate culverts (4-10 feet wide)
- Alternative A: 7
- Alternative B: 5
- Alternative C: 131
Number of major culverts (10-20 feet wide)
- Alternative A: 12
- Alternative B: 9
- Alternative C: 141
This sizing estimate does not come close to minimum fish friendly sizes for culverts. Three feet (36”) is a recipe for massive culvert failure for fish. “Fish-friendly culverts should generally match or exceed the bankfull width of the stream to maintain natural water velocity and habitat, typically requiring a minimum diameter or width of 6 feet (or at least 1.2x the stream width). They must be embedded (buried) 20–50% into the streambed to allow for sediment transport and natural passage.” [11] The USFWS guidelines utilized by the State of Alaska in permitting reiterates these minimums.
Alaska law requires that culverts in fish-bearing waters must provide free passage for all fish, mandated by the Anadromous Fish Act (AS 16.05.871) and the Fishway Act (AS 16.05.841). The Alaska Department of Fish and Game (ADF&G) requires a Fish Habitat Permit [12] for installation, often requiring designs that mimic natural stream channels (stream simulation) to allow safe passage for both juvenile and adult fish.
Key Legal and Regulatory Requirements
- Permitting Requirement: Any project involving the installation, replacement, or maintenance of a culvert in anadromous or fish-bearing waters requires a Fish Habitat Permit.
- Fish Passage Mandate: Culverts must be designed to allow free movement for fish, preventing “perched” culverts that block migration.
- Design Standards: The state prefers designs—such as stream simulation—that match the natural stream gradient, width, and substrate, allowing fish to pass through as if the pipe were not there.
- Waterway Protection: Regulations 11 AAC 95.305 require that culvert discharge points are protected from erosion to prevent downstream habitat degradation.
- Fish Passage Improvement Program: A dedicated ADF&G initiative that partners with agencies like the S. Fish and Wildlife Service [13] to identify and replace barrier culverts.
Because the Alaska Department of Fish and Game has no road authority, they entered into an April 14, 2025 Memorandum of Agreement (MOA) between the Alaska Department of Fish and Game (ADF&G) and the Alaska Department of Transportation and Public Facilities (DOT/PF) for the Design, Permitting and Construction of Culverts for Fish Passage [14] that details the permitting requirements for any construction project that would be affecting anadromous and resident fish.[15]
It is almost impossible to calculate the true cost of culverts for the Ambler Road Project. They are certain to multiple over time as more fish bearing streams and wetlands are identified, as requirements will change for permitting and as construction costs will escalate. A January 2026 cost analysis of the Ambler Road based on current assessments noted: “Fisheries data not yet collected for the proposed Ambler road may show the need for additional, costly, bridges and/or culverts. The fisheries data needed to design the road’s culverts and bridges have not yet been fully collected. The SEIS states that “Additional field study would be necessary to identify all streams and other aquatic habitats in the study area and to determine potential fish use.” [16]
Expect ultimate costs to be in the billions for culverts without any estimates for maintenance.
Culverts that are not maintained are useless to fish. Part 4 of this series will focus on related laws and the necessity of culvert maintenance.
[1] Part 2 of this series discussed how culverts impact fish passage. Part 3 will discuss general costs, as a very brief overview, of culvert installation and what that could mean to the Ambler Road Project.
[2] Gale K. Vick is a 57 year resident of Alaska with a long history of research and commentary on fisheries policy for various organizations. This is researched opinion and should not be considered definitive. Original sources should always be consulted and verified.
[4] https://dot.alaska.gov/stwddes/dcspubs/assets/aop/parks_aop.pdf
[5] Federal appropriations / Press release, Sen. Lisa Murkowski 12/5/22
[6] Alaska’s Largest Fish Passage Culvert Frees Tyonek Creek, .U.S. Fish and Wildlife Service, https://www.fws.gov/story/alaskas-largest-culvert-frees-tyonek-creek
[7] National Culvert Removal Replacement and Restoration Grant Program Year One [FY 2022] Grant Recipients https://www.fhwa.dot.gov/engineering/hydraulics/culverthyd/aquatic/2022recipients.pdf
[8] Estimating Ambler Road Construction, Maintenance, and Financing Costs Prepared by L. Epstein,1 P.E. of LNE Engineering and Policy (Anchorage, Alaska) January 2026 https://alaskawild.org/wp-content/uploads/2026/03/roadcostrptfinal26.pdf
[9] Environmental Impact Statement FINAL Volume 2: Appendices G–K March 2020 U.S. Department of the Interior Bureau of Land Management Ambler Road https://npshistory.com/publications/gaar/ambler-rd-feis-v2-2020.pdf
[10] Ambler Road Record of Decision / U.S. Department of the Interior / Bureau of Land Management June 2024 https://alaskabeacon.com/wp-content/uploads/2024/06/Ambler-Road-BLM-ROD_508.pdf P.6
[11] “Fish Friendly Culverts” University of Wisconsin, Stevens Point, https://www3.uwsp.edu/cnr-ap/UWEXLakes/Documents/ecology/shoreland/background/fish_friendly_culverts.pdf
[12] https://www.adfg.alaska.gov/index.cfm?adfg=uselicense.faqs
[13] U.S. Fish & Wildlife Service Culvert Design Guidelines for Ecological Function https://www.fws.gov/alaska-culvert-design-guidelines
[14] https://dot.alaska.gov/stwddes/dcspubs/assets/pdf/directives/attach/25/041625_moa.pdf
[15] https://www.adfg.alaska.gov/index.cfm?adfg=fishpassage.regulations
[16] Estimating Ambler Road Construction, Maintenance, and Financing Costs Prepared by L. Epstein,1 P.E. of LNE Engineering and Policy (Anchorage, Alaska) January 2026 https://alaskawild.org/wp-content/uploads/2026/03/roadcostrptfinal26.pdf