FACILITY LOCATED AT INTERSECTION U.S. HIGHWAY 160 AND ARIZONA ROUTE 264. THIS ADMINISTRATIVE ORDER UNDER SECTION 7003 OF RCRA WAS ISSUED BASED ON A FINDING THAT THE PAST OR PRESENT DISPOSAL OF SOLID WASTE AT RESPONDENTS' GASOLINE STATIONS MAY PRESENT AN IMMINENT AND SUBSTANTIAL ENDANGERMENT TO HEALTH OR THE ENVIRONMENT. THE CONTAMINATION RESULTED FROM RELEASES OF REGULATED SUBSTANCES FROM UNDERGROUND STORAGE TANKS LOCATED AT RESPONDENTS' GAS STATIONS AND SPREAD FROM NAVAJO NATION LANDS TO HOPI LANDS, THREATENING IMPACTS TO DRINKING WATER SUPPLIES. IN ADDITION, HYDROCARBON CONTAMINATION HAS BEEN FOUND IN SURFACE SOILS AND WATER IN THE VICINITY OF A DOWNGRADIENT CULVERT WHICH CONDUCTS AN UNNAMED DRY WASH UNDER U.S. HIGHWAY 160 ON HOPI LANDS, THREATENING IMPACTS TO THE MOENKOPI WASH LESS THAN ONE-HALF MILE FURTHER DOWNSTREAM. THE ORDER REQUIRES THE RESONDENTS TO POST SIGNS, BUILD AN INTERCEPTOR TRENCH TO CONTAIN THE CONTAMINATION EMANATING FROM THE CULVERT AND TO UNDERTAKE APPROPRIATE SITE ASSESSMENT AND CORRECTIVE ACTION TO ADDRESS THE COMMINGLED PLUME OF PETROLEUM CONTAMINATION. THE NAVAJO EPA AND THE HOPI DEPARTMENT OF WATER RESOURCES COOPERATED IN THE DEVELOPMENT OF THIS CASE.