The Environmental Protection Agency (EPA) is approving an application from the Navajo Nation ("Tribe") under Section 1425 of the Safe Drinking Water Act (SDWA) for primary enforcement responsibility (or "primacy") for the underground injection control (UIC) program for Class II (oil and gas-related) injection wells located within the exterior boundaries of the formal Navajo Reservation, including the three satellite reservations (Alamo, Canoncito and Ramah), but excluding the former Bennett Freeze Area, the Four Corners Power Plant and the Navajo Generating Station; and on Navajo Nation tribal trust lands and trust allotments outside the exterior boundaries of the formal Navajo Reservation. (These areas are collectively referred to hereinafter as "areas covered by the Tribe's Primacy Application.")