U.S. Interior Secretary Ken Salazar on Tuesday called on his department’s inspector general to investigate so-called midnight oil shale leasing regulations issued in the waning days of the Bush administration. “We want to avoid the booms and busts of the past,” said Salazar, a former U.S. senator from Colorado, referring to a devastating oil shale bust on the Western Slope in the 1980s. “We want to ensure the potential development is done in a way that is environmentally appropriate."