WASHINGTON.- The Anschutz Exploration Corp. oil company decided not to drill in a Montana valley Indian sacred place that has important tribal art drawings on the Northern Plains. The Indians call this area the ’Valley of the Chiefs.’ The Indian tribes had appealed to stop drilling to the oil company. William Miller, vice president of Anschutz, said, ’We chose to forgo the opportunity. It was simply risk management.’ Richard Moe, president of the National Trust for Historic Preservation, said, ’We thought it was, by far, the best possible solution. We don’t know of another instance where a drilling or mining company has donated leasing rights to a nonprofit organization.’