Bubbling Up From The Ground
City of Boise uses geothermal to heat recreational facilities and more
By Bonnie Shelton
Photos: City of Boise
Deep below the earth’s surface near Boise, Idaho is a natural resource that people have been using for more than a century. A reservoir of geothermally-heated water flows under neighborhoods and streets, including some well-known landmarks. This sustainable heating source is used in a variety of ways, from melting snow on sidewalks to using hot water for hotel laundry to providing space heating for homes and businesses, and even heating the water that fills recreational pools.
The Boise valley’s geothermal resource has a rich and storied history dating to the late 19th century, with Native Americans from the Shoshone, Bannock, and Paiute Indian tribes using local hot springs for bathing, healing, ritualistic purposes, and negotiating peace. In 1890, what is now known as the Warm Springs Water District began providing hot water to residents and businesses in East Boise.
Today, about 300-million gallons of geothermal water are pumped out each year by the city’s heating utility. The infrastructure utilizes 20 miles of pipes underneath the downtown area to move the roughly 177 F water to more than 90 buildings throughout the system that use geothermal as a heating source.
“Nearly all commercial buildings can benefit from using clean geothermal energy in downtown Boise,” says Jon Gunnerson, the city’s geothermal-utility manager. “For any number of uses, geothermal provides a unique and attractive alternative to conventional ways of heating.”
Tapping In
The Fort Boise Community Center is one of the recreational buildings connected to the system. It is home to basketball and volleyball courts, dance classrooms, a gym, and an art center.
“The community center was one of the original buildings to connect to Boise’s geothermal system and has been a real steward of conservation of this resource, using it efficiently for space heating and heating of all hot water coming from the taps,” says Gunnerson.
Minimal electricity is required to power the system’s pumps, keeping the environmental impact of the resource lower than any other heating option. Another advantage is cost. Geothermal is not impacted by volatility in natural gas prices, so users can expect much more stability.
“The city’s geothermal-heating utility is truly innovative, and we are pleased to be a part of this historic program,” says Doug Holloway, Boise Parks and Recreation Director. “We are always looking for ways to be more sustainable and promote renewable energy within our recreational facilities, and tapping into the geothermal system is a great way to achieve both of those goals.”
Here’s how the system works:
Rainwater and snowmelt on nearby mountains are absorbed into the ground.
Beneath the ground, granite rock slowly breaks down. This is a natural process which generates heat.
The water is continually warmed by the disintegrating granite.
The water is drawn up by pumps through a fault line near the Boise Foothills.
The water is then pumped through a system of underground pipes to provide heat to buildings.
Once the heat has been taken from the water, it is injected back into the underground aquifer below the city, making it a truly closed-loop system.
A Storied Past
Boise’s geothermal-heating utility is the nation’s largest, and the city’s geothermal history has roots in recreation-facility management.
The original Natatorium Pool on Warm Springs Avenue initially tapped into the city’s geothermal aquifer in 1892. The ornate building, often referred to as “the Nat,” featured a 125-foot pool that was always kept at 98 F for visitors, thanks to geothermal heating. The building also featured a women’s parlor, dining room, steam room, and saloon. It was a popular destination for Idahoans for over 40 years until it was torn down in 1934 following a storm that badly damaged the building.
Today, the legacy of “the Nat” and its early geothermal use lives on in the Natatorium and Hydrotube recreational complex that is next door to the original location. Operated by Boise Parks and Recreation, the water in the Natatorium Pool and Hydrotube Slide remains heated by geothermal, as does the pool’s operations building.
“We’re proud to continue the legacy of using this renewable natural resource to heat the Natatorium Pool and Hydrotube,” adds Holloway. “We understand this heat source isn’t available in every city, but want to encourage other recreation managers to think outside the box and aim to be more sustainable.”
The Natatorium Pool isn’t the only facility utilizing geothermal energy. Boise’s Downtown YMCA also uses geothermal to heat its showers, swimming pool, hot tubs, and tap water.
A Bright Future
While the city’s geothermal program has many benefits, there are some barriers to businesses and homeowners tapping into the system. Much of the infrastructure lies in the downtown core due to its proximity to the foothills. That means potential customers farther away from downtown don’t have the opportunity to take advantage of the natural resource. However, the city has plans to expand the geothermal-heating utility in the coming years.
That’s good news for those already reaping the benefits of the system, including the parks and recreation department, although it means the planning must begin now for additional budget and infrastructure to potentially connect other city pools or recreational facilities to geothermal.
“We look forward to what the future holds,” says Holloway. “Boise is on the cutting edge, and the more we can utilize this clean, natural resource, the better we can serve our customers.”
Bonnie Shelton is the Boise Parks and Recreation Communications Manager. Reach her at bshelton@cityofboise.org.