Denver auditor Tim O’Brien plans a fresh review of a large portion of Denver International Airport’s $2.1 billion expansion after a follow-up of a 2023 audit found persistent oversight problems. “I’m concerned,” O’Brien said. “What we are recommending goes beyond just documentation. The whole procurement of contracts and subcontracts needs to be open and fair and competitive.” DIA officials on Tuesday said they aren’t considering any changes. “The airport remains confident that it has adequate controls in place to ensure proper oversight of its projects,” airport officials said in an emailed response to Denver Post questions. Launched in 2018, DIA’s expansion was budgeted to cost up to $770 million and be done within five years.