AltaRock Energy Inc., the Sausalito, Calif.-based firm trying to tap into geothermal energy by creating rock fissures in Geysers Geothermal Field in Lake County, Calif., suspended operations on Sept. 2 because of “physical difficulties” encountered when drilling the first 12,000-ft well. The project, funded by $6 million in federal funding along with private money, was controversial because of the possibility that the rock-drilling would trigger earthquakes. The engineered fissures are created by using a hydraulic pressure of up to 4,000 psi to “hydroshear” existing fractures, causing them to open slightly and slip.
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.