Northern Cheyenne Utility Commission (NCUC) notified the EPA on May 16, 2018 about a waterline that had broken on May 15, 2018, at the Lame Deer Public Water System (System). A large portion of the System was without water resulting in complete pressure loss on the east and south sides of town. Indian Health Services (HIS) reported pressure loss at the IHS facility located on the north side of town. The EPA determined that pressure loss could present imminent and substantial endangerment to the persons served by the System