The public authority overseeing the new Minnesota Vikings stadium and the main contractor building it are headed for a three-day mediation session next month over some disputed costs.

Minnesota Sports Facilities Authority Chairwoman Michele Kelm-Helgen said Wednesday that the commission and Mortenson Construction are going before a mediator starting Nov. 9 to determine who should pay for $15 million in unforeseen costs resulting from changes to the $1 billion project. She told a legislative panel that taxpayers won’t face additional exposure because the public share is capped and a $29 million contingency fund remains available.

The mediation is private. If it fails the dispute could head for arbitration.

The stadium is more than 70 percent complete and slated to open next summer. The Vikings are covering about half the costs.