Representative image of a snow-covered mountain highway using underground geothermal heat to melt ice and snow. Image Credits: ChatGPT.
In the winter of 1948, a steep stretch of road in Klamath Falls, Oregon, became a test site for geothermal energy. When US 97 was rerouted through downtown Klamath Falls in 1948, the new road included an adverse 8% grade approaching a traffic signal, where winter conditions created traction problems for vehicles, according to the Geo-Heat Centre Quarterly Bulletin . A 419-foot geothermal well transferred heat through a downhole heat exchanger to a 50:50 mixture of ethylene glycol and water, which circulated through a grid of ¾-inch iron pipes installed three inches below the concrete surface and spaced 18 inches apart.
Instead of relying on ploughs, salt or other conventional methods, engineers embedded a network of metal pipes beneath the pavement and used underground heat to warm the road. The Oregon Highway Department incorporated a geothermal pavement de-icing experiment into the project.
The reconstruction project cost approximately $115,000, according to the Geo-Heat Centre Quarterly Bulletin, and the redesigned system covered about 22,000 square feet of road and bridge deck. It was built to provide enough heat to keep the surface clear of snow at temperatures as low as -10°F. Because it showed a principle central to hydronic pavement heating: heat can be transferred through pipes buried inside a road or bridge deck to warm the surface from below, the experiment was significant.
A later paper in Advances in Civil Engineering described the Klamath Falls installation as the first hydronic pavement heating system using geothermal energy and noted that the approach helped establish a technology that has since been studied with geothermal, solar and other heat sources. For Klamath Falls, however, keeping the system working was more complicated than simply tapping underground warmth. The geothermal well’s output declined over time. Water temperatures at the well declined, reducing the amount of heat available to the system. In the early 1990s, engineers modified the well by extending the downhole heat exchanger so it could reach hotter water at greater depth. The changes allowed the system to keep supplying heat to the pavement without relying on the original setup. What began as an attempt to make a steep Oregon road safer for vehicles ultimately became a long-running demonstration of how geothermal energy could be adapted for winter road maintenance, with the experiment continuing to shape the way engineers approached snow and ice control.
