Permafrost is melting in Alaska, the fastest warming state in the United States, putting the structural integrity of its bridges at risk.
Bridge maintenance is an issue in the US, where more than 37 per cent – or 230,000 – of the nation’s bridges need repair. A 2019 analysis deemed 46,000 bridges structurally deficient while 81,000 need to be replaced. The American Road & Transportation Builders Association puts the national bridge maintenance price tag at $224 billion (US$164 billion).
The recent infrastructure bill passed by the US Congress includes
US$40 billion in federal funds for bridge construction, maintenance and repairs, including US$225 million to fix 140 structurally deficient bridges in Alaska, where just 44 per cent of bridges are in good condition.
A team of academics led by Dr Guangqing Chi, Professor of Rural Sociology and Demography at Penn State University, argues that while this funding is welcome, more is needed. “Given the high cost to build and maintain bridges in rural Alaska, and the increasing risk to their structures as the climate warms, we believe the bill is a good start but hardly sufficient for a growing rural problem,” the team writes, in an article for The Conversation.
Bridge maintenance and climate change
In Alaska, temperatures range from minus 62° Celsius to 37.8°C, which places great stress on infrastructure. Chi and his team outline the challenges of bridge construction and maintenance in Alaska. “Building bridges here is an expensive, complex process, and they require long-term maintenance that gets complicated in rural areas,” they write.
“From an engineering perspective, bridges are vulnerable to the effects of climate change. They are particularly sensitive to seasonal freezing effects, which can quickly change their mechanical properties and structural integrity.”
According to a new report, Alaska has been warming twice as quickly as the global average since the middle of the 20th century and at a rate faster than any other US state. As a result, rivers and lakes are freezing later, thawing earlier, and forming thinner ice, creating safety issues for people who rely on frozen waterways as thoroughfares.
The permafrost that lies under 80 per cent of the state is melting, which accelerates corrosion and causes other forms of damage. As a result, bridges in Alaska require frequent monitoring, which can be difficult in rural and remote settings, particularly for human inspectors.
Drones can overcome the limitations of human inspections and improve the bridge inspection process by advancing safety, reducing costs and enabling access to hard-to-reach areas.
While some jurisdictions – such as New York – are investing in drone inspection pilot programs, authorities have not trialled the technology in Alaska. The state’s government spending has fallen by 43 per cent in the past eight years due to a fiscal crisis brought about by a drop in state oil revenue, its main source of income.