CARLBAD, N.M. (AP) — U.S. officials are pushing New Mexico regulators to clear the way for a new ventilation shaft to be built at the federal government’s nuclear waste repository. But watchdog groups say modifying the permit for the Waste Isolation Pilot Plant to allow for the construction could open the door to expansion. The state Environment Department's Hazardous Waste Bureau held a virtual hearing this week to gather comments on the proposed permit change. A 2014 radiation release contaminated parts of the underground facility in southern New Mexico and resulted in limited ventilation. Officials contend more air will be needed as mining and waste operations continue.