WASHINGTON, D.C. --- A Senate committee hearing last week grew a little tense when California Senator Barbara Boxer challenged Transportation Secretary Mary Peters' assertions that the nation's infrastructure isn't facing a safety crisis. Appearing before the Senate Environment and Public Works Committee, Peters testified: "While we can and must do more to improve the quality of our nation's infrastructure, it would be both irresponsible and inaccurate to say that the nation's transportation system is anything but safe." Peters told committee members that data before the Minnesota bridge collapse suggested that the bridge was safe for use, although it had been rated structurally deficient. "How can you say that everything is rosy when 13 people died?" Boxer asked Peters. "I don't get it." More than 70,000 bridges have been designated as structurally deficient. The American Society of Civil Engineers estimates that repairing those bridges will cost at least $9.4 billion a year for 20 years. Peters said it will likely take the National Transportation Safety Board a year to determine the cause of the Minnesota bridge collapse. Peters also argued against a proposal by Rep. Jim Oberstar to raise the federal gasoline tax by 5 cents per gallon to help fund the bridge repairs. "The answer is not to spend more; it is to spend more wisely," Peters said.