The Ambler Road Project Creates Immense Challenges for Wild Fish Part 8: Sedimentation and Asbestos-Laden Soils Threaten Fish-Bearing Waters

by | Sep 30, 2026

Photo: Ambler Road SEIS Chapter 3 Maps Affected Environment

Many Alaskan salmon returning to spawn in natal streams must navigate glacier-silt laden waters.  So, what’s the big deal about sediment and run-off from mining, road construction and forever traffic?

It’s all in the topography of where salmon are at various life stages and the chemical composition of what is going into the water.

Returning adult salmon have, over thousands of years, developed adaptations that fit their return cycle journey. Some go from saltwater directly to clear water rivers; others must traverse thousands of miles of gritty silty rivers on their way back to spawning grounds. Salmon have adapted and thrived in these conditions for millennia.  Adaptations include: Gill rakers that act like combs to trap large sediment pieces and stop them from harming the delicate gill tissue, thick mucus on skin and gills to secrete extra slime that traps dirt and prevents cuts, swimming close to riverbanks where the water moves slower and holds less dirt, finding resting spots behind big rocks or in quiet side channels, not eating during their return river run, which keeps mud and sand out of their stomachs. In addition, glacial turbidity acts as a sunscreen for adult returning salmon and a predator protection for out-going juvenile salmon. “The milky white glacial waters (produced by glacial silt) act as a sun barrier for the salmon. Even wild fish are susceptible to UV-B radiation and degradation.

These adaptations and physical changes are predicated on naturally occurring water conditions, including sediments.

In the simplest terms, “Sediment is tiny pieces of solid matter, like sand, dirt, rocks, or organic bits, that are moved by wind, water, or ice and settle at the bottom of a liquid or a land area.”

In rivers like the Yukon River, this includes silt, clay, sand, gravel, minerals, soil erosion, remains of plants and animals. More than 90% of the Yukon’s glacier sediment are extremely find particles created by glaciers grinding against bedrock, with grain sizes smaller than 62.5micrometers. Sediment plays a very important part in enriching soil and water with nutrients and increasing biodiversity.

But sediments can also be a hazard.  Sediments are constantly changing form as they shift, some eventually hardening into sandstone, rock, etc.  Re-channelization of a watershed, loss of riparian habitat, melting permafrost, flooding, scouring, erosion and other sediment events can disturb or smother redds. (Female salmon dig nests in gravel, called redds, where they lay their eggs. Fine dirt and sand fill the spaces between rocks. This blocks the fresh, oxygen-rich water that eggs need to hatch and grow.)

Some “naturally-occurring” sediments, like those laden with asbestos, are toxic to fish.

Asbestos is extremely harmful to animals and fish as well as humans.  Aside from the danger of airborne fibers to humans and land animals, asbestos fibers entering the watershed can significantly harm fish by damaging gills, building up toxins in organs, creating tumors and swelling and creating balance issues.  Layering fibers can smother fish. Because asbestos does not dissolve, degrade, or break down biologically in water, it forms a persistent, hazardous blanket over critical underwater zones. Asbestos fibers especially affect juvenile fish as well as micro-invertebrates that fish feed on. Severe chronic exposure during early life stages has been shown to stunt growth and cause complete mortality in developing larval cohorts over extended periods. Asbestos exposure induces behavioral and anesthetic-like stress, causing fish to become ataxic (losing motor coordination) and lose their physical equilibrium. Studies on coho salmon show that chrysotile asbestos causes physical distortion of the lateral line region. (The lateral line is a sensory organ fish use to detect vibrations, depth, and movement in the water. When damaged, fish experience severe orientation aberrations, losing the ability to track moving prey (feeding) or accurately sense the movements of potential partners (mating.) Asbestos fibers suspended in water physically scrape against the fish’s body. “This leads to epithelial hypertrophy (thickening of the skin tissue) and physical abrasion of the gill lamellae. The resulting respiratory distress leaves the fish too weak and lethargic to actively forage or participate in highly energetic courtship behaviors.” Trace minerals like nickel and manganese are also often found in asbestos and are toxic to fish.

Both animals and humans that eat fish that have ingested asbestos can be harmed, Studies of humans being directly harmed by eating fish that ingested asbestos fibers are largely inconclusive. However, it is well known that ingested asbestos can lead to digestive cancers in humans. People exposed to airborne asbestos fibers as a result of disturbance are likely at a much higher risk.  A diet high in local fish in an exposed area should be a studied factor.

Naturally occurring asbestos (NOA) is all over Alaska.  “Alaska has large known deposits of ultramafic and serpentine mineral ore throughout the state containing naturally occurring asbestos (NOA).  There are four major asbestos-rich areas throughout the panhandle region.  Two of these areas are located in Juneau and Ketchikan and the other deposits are found along the Yukon River around the Kobuk Valley and Wrangell-St. Elias National Parks. Specific to the Ambler Road project are several areas that are high asbestos risk, including, but not limited to:

  • The Cosmos Hills:Located roughly 13.5 miles east of Ambler, Alaska, this area is a significant known source of serpentinite rock, which poses a high asbestos risk.
  • The Jade Mountains:Positioned about 7.5 miles northwest of Ambler, this region consists of partially serpentinized peridotite and dunite, presenting another heavily documented high asbestos risk
  • The Angayuchum Terrain:This broader mountain range encapsulates both the Jade Mountains and the Cosmos Hills. The SEIS identifies mafic volcanic rocks throughout this terrain as posing moderate to high asbestos risks.

“Naturally Occurring Asbestos (NOA) is found in mineral deposits in rock and in soils derived from rock sources.  Asbestos is a generic term for several different naturally occurring silicate minerals with long, thin fibrous crystals.  Once a widely used commercial material, asbestos has been known since the 1980s to be a human carcinogen.  Mining and use of asbestos in manufactured products is banned. Due to geography, limited road systems and relatively sparse and scattered population centers within Alaska, NOA has not been a historical concern for the state. However, over the past several years NOA has been encountered in Alaska and has impacted some DOT&PF projects (e.g. Dalton Highway, Ambler, etc). DOT&PF has an ever-increasing demand for gravel and rock to construct and repair its roads and airports. Large construction projects such as the proposed roads to resources, gas pipeline and railroad extension will require large quantities of gravel and rock sources.  Unfortunately, some localities in Alaska that have a demand for rock and gravel do not have nearby sources that are NOA-free. This impacts the cost of such projects when DOT&PF is required to haul rock and gravel long distances by road or barge.”

Six naturally occurring asbestos (NOA) minerals (chrysotile, amosite, crocidolite, fibrous tremolite, fibrous anthophyllite, and fibrous actinolite) are regulated through testing and the use of construction materials in Alaska Department of Transportation & Public Facilities (DOT&PF) statutes. Other unregulated asbestiform minerals are known to occur in Alaska and may have similar health concerns as the regulated asbestos minerals (data table of known asbestos occurrences).”

How does asbestos get into watersheds?  Naturally occurring asbestos (NOA) enters a watershed when geological formations containing asbestos are broken down or disturbed, allowing the microscopic, insoluble mineral fibers to wash into nearby water systems. Because asbestos minerals (like chrysotile or tremolite) are highly resilient and do not dissolve, degrade, or evaporate in water, they remain suspended and travel long distances downstream. Asbestos disturbance releasing fibers into rivers eventually finds it way to marine estuaries.

“Asbestos does not dissolve like many chemicals. When asbestos-containing materials weather, break or are mishandled, they can release small mineral fibers. Surface water, drains, wind and floodwater may then carry fibers away from the original source…. Poorly controlled washing and runoff give that contamination a route to water.”

Naturally occurring asbestos is harmless unless disturbed which can cause potential health hazard. “Disturbing these fibrous minerals through geological processes such as weathering and erosion or human activity can release tiny asbestos fibers, as dust too small to see, into the air, creating an environmental health concern.”   Natural conditions (weathering) can leach asbestos into Alaska’s rivers,  but the major threat of asbestos leaching is from construction and mining where crushed rock for gravel or simply moving rocks and soil around can release significant amounts of asbestos. Gravel mining, storm run-off from unpaved road dust, degrading road systems, road grading, trenching, and just traffic all contribute to the high potential for asbestos entering the watershed.

While there are strict requirements for projects that might disturb NOAs, there is very little than any project can do to mitigate asbestos impacts on fish and water invertebrates from run-off into streams.

The potential for naturally occurring asbestos to be disturbed and enter the adjacent watersheds in the Ambler Road Project is extremely high.  Building up a 211 mile road in the wilderness calls for a massive amount of moving locally found gravel, much of which is likely to be asbestos laden. Because the planned industrial corridor traverses northwest Alaska’s Brooks Range foothills—a region dense with natural serpentinite and asbestos-containing mineral deposits—finding entirely asbestos-free gravel is a known logistical challenge.

Abatement measures to protect watersheds in the Ambler Road Project area are poor. The containment and mitigation of Naturally Occurring Asbestos (NOA) is a highly critical issue for the Alaska Industrial Development and Export Authority (AIDEA) regarding the planned 211-mile industrial haul road cuts through remote terrain laden with natural asbestos bedrock, construction, drilling, and material hauling risk releasing microscopic fibers into the surrounding Brooks Range watershed—which feeds crucial salmon and subsistence rivers like the Kobuk River.

AIDEA’s reliance on existing “guidelines” for asbestos containment is arguably misguided at best. Appendix 4-F of the Alaska Department of Transportation and Public Facilities (DOT/PF) asbestos guidelines outlines the Interim Guidance and Standards for Naturally Occurring Asbestos (NOA) Material Use. “This document provides interim guidance to owners and contractors regarding use of Naturally Occurring Asbestos (NOA) material within the State of Alaska.  Asbestos fibers are a known health risk. Under new state law signed in May 2012, DOT/PF is charged with reviewing and approving plans using NOA material, if the owner or contractor using the NOA material seeks immunity under state law as provided in House Bill 258 (HB 258)”.  But DOT/PF’s “Best Practices for the Use of Naturally Occurring Asbestos” does not, for instance, provide guidance on asbestos entering watersheds.  Additionally, most of the guidance is largely impractical and unenforceable on large projects, creating hazards for both humans and animals.

Future articles will discuss tire run-off, mining discharge and failure threats to wild fish. 

References and Further Reading: