| Abstract |
The geothermal springs near Boise Idaho have a long history. They were originally used by Native Americans, then by trappers, miners, and early settlers along the Oregon Trail. Development began in 1890 when the first two wells were drilled to supply hot water to a natatorium and houses being constructed in east Boise. This system, currently referred to as the Boise Warm Springs Water District (BWSWD) continues to operate today serving approximately 350 houses and businesses. Additional wells were drilled in the 1980’s by the City of Boise, the State of Idaho and the Veterans Administration to develop a geothermal district heating system within each of their service areas. Today, Boise is site of the nation’s oldest and largest geothermal district heating system and may well boast as one of the largest in the world. The geothermal resource is a fault controlled system within cretaceous rocks of the Idaho Batholith. Geothermal fluids move up a fault-fracture system along the Boise foothills to the northeast of the city with outflow within interbedded basalt, porphyritic rhyolite and sandstone/conglomerate units underlying the Boise area. The City of Boise, the Veterans Administration and the BWSWD wells produce from the fractured granitic rocks associated with the Boise Front Fault while the wells supplying the State of Idaho system are developed in the porphyritic rhyolitic units. The City of Boise system currently heats over 90 commercial, government, and institutional buildings comprising over 6 million square feet (557,418 square meters) of space utilizing 177°F (80°C) geothermal water. In addition to the historic geothermal district heating system, a commercial green house was started in 1930 and continues to provide fruits and vegetables to residents of Boise. The State of Idaho geothermal heating complex heats 11 state owned buildings totaling approximately 800,000 square feet (74,322 square meters) including the state capital building, which is the only US state capital being heated by geothermal energy . The US Veterans Administration system heats 19 buildings totaling approximately 500,000 square feet (46,452 square meters) of space. The City of Boise, the State of Idaho, the Veterans Administration and the Warm Springs Water District heating systems make an approximate total of 7.5 million square feet (696,773 square meters) heated by geothermal resources. Although primarily utilized for space heating, these systems also heat domestic water, sidewalk-snowmelt systems, recreational pools, laundry facilities and other direct use applications. jgunnerson@cityofboise.org roymink@gmail.com |