Like many other territories across the American West during the mid-to-late-19th century, Arizona was subject to heavy prospecting in search of gold, silver, copper and other valuable minerals and ores. Years later in the 20th century, deposits of both asbestos and uranium were also identified and mined around the Grand Canyon from the 1950s through the mid-1980s.
Unfortunately, many of these abandoned mines ended presented significant hazards to public health including loose rock falls, unsecured vertical mine shafts with high radon concentrations, and leaching of toxic metals and asbestos. Still worse, many of these Arizona mines were located in National Parks and ecologically important wilderness areas, and thus they proposed environmental damages in addition to human health and safety impacts.
In 2010, the National Parks Service (NPS) selected 139 high priority Arizona mines located in Coronado National Memorial, Grand Canyon National Park, Organ Pipe Cactus National Monument, and Saguaro National Park for permanent closure and reclamation.
During the planning phase, NPS was required to carry out an environmental review under the National Environmental Policy Act (NEPA). This review process is designed to ensure federal agencies identify and publicly disclose any potential environmental, public health, or economic impacts a proposed action may have.
Using the NEPA process, NPS solicited input from surrounding communities and tailored specific mine closure activities for each feature in the four parks. The Environmental Assessment also identified specific mitigation measures that would be taken to protect several endangered species, most notably the long-nosed bat.
 “Abandoned Mine Lands Closure Plan and Environmental Assessment available for public review and comment.” Grand Canyon News. February 16, 2010. https://www.grandcanyonnews.com/news/2010/feb/16/abandoned-mine-lands-closure-plan-and-environment/
 “Proposal to Close Abandoned Mine Lands (AMLs) within Coronado National Memorial, Organ Pipe Cactus National Monument, Saguaro National Park, and Grand Canyon National Park.” U.S. Department of the Interior. April 12, 2010. https://www.fws.gov/southwest/es/arizona/Documents/Biol_Opin/090452_NPSMineClosure.pdf
 “Proposal to Close Abandoned Mine Lands Environmental Assessment.” National Park Service. https://parkplanning.nps.gov/projectHome.cfm?projectID=24740