An inside look at the largest geothermal heat system in the US

Posted at 12:46 AM, Dec 06, 2018

BOISE, Idaho — Two high-profile geothermal water-line breaks in Downtown Boise have residents a bit concerned — especially since the city has plans to expand the system.

But the City of Boise said the leaks were a lot less dramatic than the cool air mixed with steam made them look (images show bright green colors in the air), and are looking forward to the future of innovative geothermal ideas.

Boise's geothermal heat system has been in full operation since the 1980s, and as usual, using water and metal is a recipe for corrosion. But the city says it is doing its best to remain proactive.

"A lot of people walk the streets of Downtown Boise and have no idea that such a big footprint of Downtown Boise is heated with this renewable, clean resource that we take advantage of in a big way every day," said Colin Hickman, communications manager in the Public Works Department for the City of Boise.

It's a system that dates back to the 1890s when Boise began using geothermal heat for Victorian homes and the original natatorium. In 1983, Boise began the geothermal heat system, now holding the record for the largest geothermal system in the United States, supplying heat to 92 buildings in Downtown Boise.

"That equates to about 6-million square feet," Hickman said.

It’s primarily used for heating buildings but it also provides heat for the YMCA pool, as well as sidewalks, providing shovel-free snow removal in the winter.

JUMP is one of the buildings that uses the system.

"It's really a smart investment for JUMP, and for our community, as it's a low cost, clean, renewable, and local energy source, it made sense on a lot of levels," said Kathy O’Neill, the community engagement director at JUMP.

The geothermal water is pumped from a well in the Boise Foothills. It's then brought downtown underneath buildings and run through pipes, where the water is sitting at 170 degrees. It's then put in a heat exchanger where it takes off about 55-degrees of that water, to heat the building.

Afterward, it's taken back to be redeposited at Julia Davis Park.

That process only started in 1999. Before then, the geothermal water was taken out of the aquifer, then disposed of in the Boise River — and aquifer levels started to decline. That happened until that re-injection site was made at Julia Davis Park, bringing aquifer levels right back up to where they began.

"The carbon footprint is almost nothing. it relies almost entirely on electricity just to pump up. There's no fossil fuel being used. It's a really clean and efficient energy," Hickman said.

It also comes with a relatively low price tag.

"As far as our overall utilities, the geothermal is not a substantial cost for the city," Hickman said.

The geothermal heating bill is costing about $1,000 each winter month for the entire downtown area. And lucky for Boise, it's a system very unique to the Western U.S.

"It really comes down to where geothermal, an aquifer is available. And so it's really, Boise is very fortunate to have this aquifer right under our streets," Hickman said.

The City of Boise's representatives said they are looking forward to expansion plans and new innovative uses of the geothermal system.