CASPER, Wyo. (AP) — A Virginia-based company that is among the largest coal miners in Wyoming's Powder River Basin has been informed it no longer meets the state's self-bonding requirements, which could mean it will have to come up with millions in three months to cover any cleanup obligations here. In a statement issued Friday, Alpha Natural Resources disagreed with the state's assessment and said it is working to have the decision changed, the Casper Star-Tribune (http://tinyurl.com/pejdf8w) newspaper reported. Self-bonding status allows a mining company to agree to pay for future cleanup costs associated with its operations without putting down collateral, provided it meets certain financial criteria.