MW of electricity, enough to supply 24,000 homes. Steamboat two and three use two separate closed loops, one consisting of geothermal brine, and the other containing isobutane. Brine at 310 to 330 °F (155 to 166 °C) is pumped from nine underground wells using nine 450 horsepower, motor-driven, sixteen-stage vertical centrifugal pumps. The wells extend 590 to 2700 feet (180 to 823 meters) below ground and were drilled through fractured granite. Drill bits, at a cost of $10,000 to $20,000 each, were replaced after only 20 to 30 feet (6 to 9 meters) of drilling. Each well pumps an average of 1800 gallons (6813 liters) per minute. A bubbler tube is used to measure brine levels. By monitoring these levels, operators know they are not drawing down the underground reservoir. The water pressure never varies, and well levels are very stable. The brine remains a pressurized liquid as it is piped to twelve forty-foot long heat exchangers. Heat exchanger pressures and temperatures are controlled to minimize fouling. As the geothermal brine is piped through one side of the heat exchanger, isobutane is pumped through the other side by six horsepower pumps. Isobutane's 11 °F (-12 °C) boiling point makes it a good medium for use in a binary plant. Writings In 1935, state engineer Alfred Merritt Smith wrote about Steamboat Springs: “Geologically, the springs are among the most interesting in the world, for they demonstrate in a striking way how mineral veins and deposits are formed. The hot water is constantly depositing silica, gold, silver, mercury, antimony, and other minerals and metals, which it holds in solution. The silica is held in solution as a jelly-like colloid, and upon the evaporation of the water is deposited as translucent gelatinous silica, which on the surface is gradually dehydrated to become amorphous white sinter. In cracks and crevices, the silica becomes banded chalcedony, or even quartz. The metals are deposited simultaneously with the silica. One of the most beautiful mineral specimens in the well-known Mackay School of Mines Museum at Reno is a mass of intermixed dazzling white silica, crimson cinnabar, and meta-stibnite from Steamboat Springs.” Name Mark Twain wrote in August 1863 "... From one spring the boiling water is ejected a foot or more by the infernal force at work below, and in the vicinity of all of them one can hear a constant rumbling and surging, somewhat resembling the