× Thanks for reading! Log in to continue. Enjoy more articles by logging in or creating a free account. No credit card required. Log in Sign up {{featured_button_text}}

Wyoming’s largest coal mines would effectively be banned from self-bonding if the proposed rules that passed an advisory board Wednesday make it through one more round of public input and onto the governor’s desk.

At a sparsely attended meeting in Casper, citizen members of the Land Quality Advisory Board voted 4-1 to require strong credit ratings for companies that want to self-bond.

The credit rating would determine whether a company is financially healthy enough to guarantee millions of dollars in cleanup costs without securing a form of insurance. Wyoming has the largest open surface coal mines in the country and the money required to return those mine sites to open prairie or ranchland someday is significant — both as a potential risk to the state and as a cost carried by companies in a difficult coal market.

The state is also proposing that mines have at least five years of production remaining in order to qualify for self-bonds, and that even companies that qualify for self-bonds hold a percentage of their reclamation obligation in more secure channels so the state has faster access to cash if a company dissolves.

Under the new rules, the massive mines in Wyoming that produce about half the country’s thermal coal are less likely to become a state liability if companies bust, regulators say.