In 1948, Oregon buried geothermal pipes beneath a steep section of US 97 to melt three inches of snow an hour; the system operated for nearly 50 years before its iron pipes corroded

In the winter of 1948, a steep stretch of road in Klamath Falls, Oregon, became a test site for geothermal energy. 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. According to the Geo-Heat Centre Quarterly Bulletin, 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. The Oregon Highway Department incorporated a geothermal pavement de-icing experiment into the project. 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.Turning underground heat into a snow-free roadGeothermal water was not piped directly beneath the road surface. Instead, the well supplied a downhole heat exchanger, which transferred heat to a closed-loop system containing a glycol-water mixture. The same circulation fluid could then move continuously through the pavement heating system. The Geo-Heat Centre Quarterly Bulletin reported that the system was initially estimated to provide about 350,000 Btu per hour at a flow rate of 20 gallons per minute. At a flow rate of 50 gallons per minute, the reported heat output was about 900,000 Btu per hour. The system was designed to keep the pavement clear of snow at temperatures as low as -10°F, including during snowfall rates of up to three inches per hour.The experiment was significant 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. 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.Nearly five decades beneath the pavementUltimately, the most problematic issue emerged in relation to the pipes. In less than 50 years, corrosion of the original iron grid caused leaks, and by 1997 the system had failed. The failure did not end the use of geothermal energy for snow melting in Klamath Falls. Instead, the system was reconstructed in 1998, with the original iron grid replaced by a network of PEX piping, or cross-linked polyethene, better suited to the demands of the site.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. 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.Catch the latest World News and Live updates. Download the TOI app.