America’s bridges are in bad shape. Of the approximately 620,000 bridges on roads, rivers and other waterways across the US, more than 43,500, about 7%, are considered “structurally low”.
In Alaska, as the planet warms, bridges face a unique and growing problem.
Permafrost, the frozen ground beneath large parts of the state, is melting with the changing climate, and it is changing the soil and everything on it. Bridges are also increasingly important for rural residents who can no longer rely on the stagnation of river ice in spring and fall.
The infrastructure bill that made its way through Congress currently includes US$40 billion in new federal funds for bridge construction, maintenance and repair – the largest investment in bridges since the construction of the Interstate Highway System in the 1950s. was started in That funding has about $225 million to address 140 structurally deficient bridges across Alaska.
Given the high cost of building and maintaining bridges in rural Alaska, and the increasing risk to their structures as the climate warms, we believe this bill is a good start, but Hardly enough for a growing rural problem.
As the planet warms, the growing need for bridges
Alaska is warming faster than any other US state. As Alaska’s temperature rises, rivers and lakes later freeze, melt first and form thin ice.
When the snow is unstable or unpredictable, those dependent on the river crossing are trapped and the risk of snowmobile fatalities increases. Rural residents often use rivers to travel between communities, either as snowy roads in winter or waterways in summer, and they often use rivers to hunt, gather traditional foods, or access health care facilities. have to cross.
Alaska has just over 1,600 bridges that are open to the public—the fourth lowest total of any state, despite being the largest state by land area. Only 44% of those bridges are considered to be in good shape.
Mark Ralston / AFP via Getty Images
The construction of bridges here is an expensive, complicated process, and they require prolonged maintenance which becomes complicated in rural areas. This is a challenge with two important aspects: one is structural, and the other is human.
Engineering: the problem of permafrost
From an engineering point of view, bridges are vulnerable to the effects of climate change. They are particularly sensitive to the effects of seasonal cold, which can quickly alter their mechanical properties and structural integrity.
Alaska has some of the toughest conditions for infrastructure, with temperatures ranging from minus 80 degrees Fahrenheit (minus 62 Celsius) to over 100 F (37.8 C). Snowfall can reach up to 81 feet (24.7 m) per year in some areas, and 80% of the state is covered with snow-rich permafrost.
One of the most important factors affecting the service life of a bridge is the corrosion of the reinforcing steel. As the permafrost melts and the water becomes liquid, it can accelerate corrosion and cause other types of damage.
A variety of techniques have been used to reduce the effects of cracking, but damage from freezing and thawing still plays a significant role in limiting the lifespan of a bridge. Once the bridge is built, regular monitoring is required to ensure that it remains in good condition. This is difficult in areas that are remote and where harsh weather can be challenging.
AP. Via Alaska Department of Transportation and Public Facilities
Another major engineering challenge for rural areas is human-dependent bridge inspection, which limits how often bridges can be inspected and presents significant safety risks to inspectors. An exciting development in maintenance involves advances in drone technology. Bridge inspections can be done safely by drone at more reliable intervals, but there is an investment involved.
Read more: Melting Arctic sends message: Climate change is here at large
Higher cost and better planning
Building infrastructure, especially in rural Alaska, already comes with a hefty price tag.
The cost of delivering steel and concrete to a remote location, sourcing available local materials, and bringing in outside specialized labor can significantly add to the cost of a bridge. For example, a 2015 construction cost survey in Alaska found that home construction based on materials alone is three times more expensive in Barrow, a remote community in Alaska’s North Slope, than in Anchorage, the state’s largest city. .
Andrew Burton / Getty Images
In rural Alaska, the process of building bridges is complicated and can take years. It depends on cooperation, often between multiple communities, on navigating state processes and on the support of political leaders. From the outset it is important to understand how building the bridge will affect the well-being of the community and how communities can work together on funding, design, construction and maintenance.
Our team of engineers and social scientists is working on a guide to successful bridge funding, construction and maintenance for remote areas that establishes a community-driven process.
Alaska has no income tax or statewide sales tax and is facing a financial crisis due to declining state oil revenues. Federal infrastructure investments can help direct funding to rural bridges that may otherwise continue to deteriorate.
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