Facing a crisis after a huge crater formed in the main flood-control spillway at Oroville Dam, officials at the California Department of Water Resources called in an old hand to help: David Gutierrez, a nationally known engineer who had just retired as chief of the agency’s dam-safety division. He seemed like an obvious choice for dealing with an emergency at America’s tallest dam – valued for his technical expertise, his coast-to-coast connections in the engineering field, and his years of experience.