In the early 1950s, fifteen investor-owned utility companies operating in the Ohio Valley formed the Ohio Valley Electric Corporation and its wholly owned subsidiary, Indiana-Kentucky Electric Corporation. Until 2005, Indiana-Kentucky Electric Corporation's Clifty Creek Powerplant had a single primary customer, the Portsmouth Area Uranium-Enrichment Complex of the U.S. Department of Energy at Piketon, Ohio. Since beginning operation in 1955, the plant has been a steady regional employer. It generates energy with steam turbines using water from the Ohio River, while barges deliver 4.5 million tons of coal each year to six giant boilers, each holding 52,000 gallons of water. Each day, 1.4 billion gallons of Ohio River water cycle through the plant as it produces enough electricity to power a city of one million people. As built between 1953 and 1956, the complex included three 683-foot stacks visible for miles. In 1978-1979, those were replaced by two taller, more efficient stacks 985 feet high, 77 feet in diameter at the base, and 34 feet at the top, built along with new electrostatic precipitators to remove particulate matter from flue gas. Since its original construction at a cost of $158 million, the plant has spent more than $360 million on environmental upgrades, including scrubbers to remove harmful emissions scheduled for completion by 2010 at a cost of $460 million. The ash produced by burning coal at the plant is recycled and sold to concrete manufacturers.