Tribal Authority Rule, to provide tribes with more control over enforcement of clean air quality. The company abandoned the plant and related mine, due in large part to increased costs of electricity and competition from cheaper Chinese phosphate. Seventeen mines in the region have been designated as Superfund sites because of selenium poisoning. Since 2001, FMC has been working on cleanup at the reservation. The tribe has developed its own expertise in air, water and land quality, but its resources are still seriously threatened by the extensive cleanup needed. The Shoshone-Bannock Tribes chose to participate in the Department of Interior's Native Nations Land Buy-Back Program, established after 2009 as part of the government's settlement of the Cobell v. Salazar class action suit over mismanagement of fee/lease accounts. Under this program, the government is buying back fractional interests in lands within reservations to put the land into trust for the communal use of the tribes. It is an effort to restore some of the lands lost following the 19th century allotment process and reduce fractional holdings too small to use readily. In July 2016, the Department of Interior made offers to 536 landowners with fractional interests at Fort Hall Reservation for buy-back of lands valued at $11 million. In total by July 2016, the Department of Interior had put about 1.5 million acres of land into trust for tribes under this program. Relations with the city of Pocatello became strained in April 2016 after the tribes learned that the city had contracted with Pocatello Solar, based in Boise, to lease a new property at the airport. The tribe was consulted by FAA officials, who are handling the environmental assessment for the project, but they learned that the company was prohibited by the city from entering into any written agreement with the tribes. They are worried about getting stuck with an operation that could cause environmental damage. Economy In the 21st century, the tribes employ nearly 1,000 Native and non-Native people in various trades: 575 in tribal government, 85 by the enterprises, and more than 300 in gaming. Since the late 20th century, the Tribes have developed the Fort Hall Casino and two smaller satellite casinos on the reservation. They are all operated by the Shoshone-Bannock Tribes, who use the revenues for additional economic development and to support education and healthcare for the people. The combined payroll of the various activities is