The U.S. Geological Survey estimated in 2013, "more than 100 million people in the United States, about 35 percent of the population-received their drinking water from public groundwater systems." The Safe Drinking Water Act, passed in 1974, sought to protect drinking water by establishing the Underground Injection Control (UIC) Program in the Environmental Protection Agency (EPA). The UIC Program, as administered by the EPA, contains regulations for injection wells to prevent endangering drinking water sources.