For those who prefer a less American-centric metric: 8,000–9,000 feet is approximately 2.5 kilometers. 15,000 feet is about 4.5 kilometers — roughly the height of 14 Eiffel Towers stacked on top of each other!
The usual value for the geothermal gradient is 25 to 30 degrees C per kilometer. So at 2.5km, in most locations they might be able to get boiling water, but not superheated steam. Most of the geothermal enthusiasts are talking about needing to go down 4 to 12 kilometers. Is there something special about the geology at this site?
Beaver County, Utah, has at least one hot spring, and I suspect more than that. I'm pretty sure that the location for this project was not chosen at random.
The US has long been the world's leading producer of geothermal power, mostly generated from this basin.
It's not a fully renewable resource. It's possible to pull out too much heat too and deplete the resource. The entire geothermal heating of the planet is only 50 terawatts, which seems big, but it's spread over 500 million square kilometers. Or 100KW/km^2, which is not much. Solar is orders of magnitude larger.