WATFORD CITY, N.D. — Three years ago, the local government in this small town faced a big challenge. At the epicenter of the Bakken Shale oil boom, people were pouring into Watford City and its 30-year-old high school badly needed replacing. The school district came up with $54 million in loans and grants to build the classrooms, and the city government borrowed $94 million to build a complex including a football stadium and an indoor event center. The various loans are backed by property taxes, sales taxes, and the local share of state oil and gas taxes. If the oil industry recovers from its current three-year oil bust, Watford City will have plenty of tax money to pay off the loans, and the industry will carry most of the financial burden. But Watford City's taxpayers could be on the hook for those loans if the oil industry falters and tax revenue falls short, which has already happened once.