Marketplace: What looks like a decorative pond at Fort Knox is actually the heart of a geothermal cooling system for the server farm powering the Army's human resources database. Water piped from the air-conditioning system gets cooled to 57 degrees at the bottom of the 25-foot-deep pond, then returns to the building, saving $10,000 a month.
The Obama Administrations Clean Power Plan, unveiled in June, requires every state to reduce greenhouse-gas emissions from power plants. But some states have tougher...