Subtitle I of the Resource Conservation and Recovery Act, as amended by the Hazardous Waste Disposal Act of 1984, brought underground storage tanks (USTs) under federal regulation. EPA implements the underground storage tank (UST) program in Indian country, providing support to tribal governments to prevent and clean up petroleum releases from USTs. The UST program in Indian country includes marketers and nonretail facilities that have USTs. Marketers include retail facilities such as gas stations and convenience stores that sell petroleum products. Non-retail facilities include those that do not sell petroleum products, but may rely on their own supply of gasoline or diesel for taxis, buses, limousines, trucks, vans, boats, heavy equipment, or a wide range of other vehicles. Of the more than 560 federally recognized tribes about 200 have federally-regulated underground storage tanks on their lands. Of those 200 tribes, over half have 10 or fewer active underground storage tanks. About 20 tribes have 30 or more underground storage tanks. Data on sites managed by this program is assembled by the EPA Regional Offices and varies from region to region in scope and content. Not all regions include Indian Nations. Publicly available data is limited to Excel spreadsheets, but regional contacts are also available to answer questions about the data. Data is updated in May and November of each year.