the project in 2016. After the rise of shale gas in the United States, natural gas power prices ($32/MWh) fell under the cost of coal power for NGS ($38/MWh), and NGS production decreased. The owners require a potential new owner (such as the Navajo Nation) to assume responsibility of future cleanups. Design and specifications The plant had three identical 750 MW steam electric generating units. Major components of each unit included a boiler, turbine, generator, closed-cycle cooling system, and environmental control equipment. The boilers were tangentially fired, balanced draft, reheat type steam generators, supplied by Combustion Engineering. Designed for supercritical operation, each boiler supplied up 5,410,000 pounds of steam per hour to the turbines at 3500 psi (241 bar) and 1000 °F (537 °C). The main turbines are General Electric (GE) tandem compound reheat turbines, each directly coupled to a generator and designed to rotate at 3600 rpm. Steam discharged from the turbines entered a condenser where water circulating through tubes cools and condensed it, producing a vacuum that maximized the pressure drop across the turbine. The heat picked up by the circulating water was removed by evaporation in six induced-draft cross flow cooling towers (two per unit). The plant used about of water per year from Lake Powell, or about 1/2 gallon (1.9L) per kWh, mainly for cooling water and scrubber operation; see section #Wastewater handling. The plant consumed about 8 million tons of low sulfur bituminous coal each year, supplied by Peabody Energy's Kayenta Mine near Kayenta, Arizona. The coal was hauled 75 miles from mine silos to the plant by the Black Mesa and Lake Powell Railroad that is owned and operated by the plant. Characteristics of the coal in 2011 included a sulfur content of 0.64%, an ash content of 10.6%, and higher heating value (HHV) of 10,774 Btu/lb. The plant had three 775 ft (236 meter) tall flue gas stacks, listed among the tallest structures in Arizona. The stacks were constructed of reinforced concrete, supporting an internal metal liner. The plant's original stacks were demolished in the late 1990s after being replaced by larger diameter stacks of the same height, resulting in the plant having up to six stacks visible for a time. The new stacks were required to accommodate cooler flue gas saturated with water vapor that resulted when wet SO2 scrubbers were added. Performance The plant had a net nameplate capacity of 2250