| Title | City of Boise Geothermal District Heating System |
|---|---|
| Authors | Neely, Kenneth; Galinato, Gerry; Johnson, Kent |
| Year | 2006 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Direct Use; Idaho, Idaho Department of Water Resources, geothermal, low temperature, district heating, space heating, ground water management area, moratorium, production, injection, Boise, Boise Front, Boise State Universtiy, Zoo Boise |
| Abstract | The City of Boise (City) operates one of the four geothermal district heating systems in the downtown Boise area. The City’s system, which has been in operation since the early 1980s, withdraws 175° Fahrenheit (F) water from its wellfield located along the toe of the Boise Foothills, and currently delivers it to about 50 customers throughout the downtown area on the north side of the Boise River. The increase in net withdrawals from the Boise geothermal aquifer in the 1980s resulted in declining water levels. In 1987, the Idaho Department of Water Resources (IDWR) established the Boise Front Low Temperature Geothermal Resource Ground Water Management Area. Additional restrictions were put in place in 1988 when a moratorium on further development was issued by IDWR. In the late 1990s, the City sought to increase withdrawals above its moratorium-based ceiling of 200 million gallons a year because of a growing customer base. In 1999, the City completed a 3,213-foot injection well. Water levels in nearby wells began to recover shortly after the injection well went online and continued to rise for the next several years. Currently, about 75% of the City’s withdrawals are returned to the aquifer; the remainder is discharged into the Boise River. In 2002, an agreement between the City and the other local geothermal users was reached that allowed the City to raise its production ceiling to 230 million gallons per year, with the conditions that the City would conduct an aquifer study, and would not ask for an additional increase until January 2005. The City will soon be bringing two new large commercial buildings on-line in the downtown area. As the City continues to expand its system, including a proposed extension across the Boise River to provide service to Boise State University, there will undoubtedly be a request in the near future to raise the production ceiling. Although geological studies and computer modeling have provided a basic understanding of the Boise Front geothermal system, the following question will surface again: Can additional withdrawals from the Boise Front geothermal system be incurred with minimal effects on water levels and water temperatures? |