[9] In the 1950s and 1960s, there was a need for new electric generation in the Southwest to supply power to growing populations in southern California, Arizona and Nevada.

The US Bureau of Reclamation also needed a large source of power for running the pumps of the planned Central Arizona Project (CAP).

However, the proximity of the proposed dams to the Grand Canyon raised opposition, initially from the National Park Service and then more vigorously from a coalition of environmental groups which promoted construction of a thermal or nuclear power plant as an alternative.

Major components of each unit included a boiler, turbine, generator, closed-cycle cooling system, and environmental control equipment.

The boilers were tangentially fired, balanced draft, reheat type steam generators, supplied by Combustion Engineering.

The heat picked up by the circulating water was removed by evaporation in six induced-draft cross flow cooling towers (two per unit).

[22]: p3 The plant had three 775 ft (236 meter) tall flue gas stacks, listed among the tallest structures in Arizona.

[23][24] The new stacks were required to accommodate cooler flue gas saturated with water vapor that resulted when wet SO2 scrubbers were added.

Fine particulate measuring 2.5 micrometers or less (PM2.5), of concern for its potential effect on health and visibility, primarily results from reactions of SO2 and NOx in the atmosphere to form sulfate and nitrate aerosols.

[28] Carbon dioxide (CO2) emissions from NGS were seventh highest of all U.S facilities in 2015, largely a result of the amount of energy it produced.

[22][32] Northern Arizona and the Colorado Plateau have consistently met National Ambient Air Quality Standards (NAAQS) established to protect public health.

[36] Unhealthy days for ozone-sensitive groups – those with asthma or lung disease – are also rare in these counties despite high natural background levels in the Intermountain West.

Coconino County, with the highest occurrences, averages less than two unhealthy days per year, these occurring between March and June, suggesting a correlation with spring stratospheric ozone intrusions.

During periods when ozone readings have been highest, peak concentrations in Page were noted to be more than 10 percent lower than those at the Grand Canyon.

[40]: p.11, 8 Fine particulate (PM2.5) levels in the Grand Canyon region have been among the lowest in the nation since before NGS completed installation of SO2 scrubbers and low NOx-SOFA burners.

[41] Annual mean levels for PM2.5 in the Page area are about 3 micrograms/cubic meter (μg/m3) – one-quarter of the NAAQS standard of 12 μg/m3 and as low or lower than the cleanest U.S. cities listed by the World Health Organization.

)[44][45] In 2012, a fish consumption advisory was issued for striped bass in lower Lake Powell, raising concerns about mercury emissions from the plant.

On January 17, 2013, the EPA proposed a BART ruling to further reduce NOx emissions:The Environmental Protection Agency (EPA) is proposing a source-specific federal implementation plan (FIP) requiring the Navajo Generating Station (NGS), located on the Navajo Nation, to reduce emissions of oxides of nitrogen (NO X) under the Best Available Retrofit Technology (BART) provision of the Clean Air Act (CAA or Act) in order to reduce visibility impairment resulting from NGS at 11 National Parks and Wilderness Areas.

NGS, which was built over 35 years ago, is the largest coal-fired power plant in the West in terms of generating capacity.

It is central to the economies of the Navajo Nation and Hopi Tribe and supplies power to the states of Arizona, Nevada, and California.

[51] The ruling would require the plant to reduce NOx emissions to no more than 0.055 pounds per million British thermal units (85 g/MWh) by 2023, necessitating the installation of Selective Catalytic Reduction (SCR) equipment.

Before the plant's owners could invest in SCRs, they will have to resolve the site lease, rights-of-way for the railroad, transmission and water lines, and the coal supply agreement.

After the EPA issued a proposed BART rule[51] it solicited input from stakeholders: the Department of the Interior, the Central Arizona Project, the Navajo Nation, the Gila River Indian Community, the Salt River Project, the Environmental Defense Fund, and Western Resources Advocates who as a technical working group negotiated a "Reasonable Progress Alternative to BART" which was submitted by the Department of the Interior to the EPA on July 26, 2013, for consideration in development of a final rule:[4][55] The Parties shall submit this Agreement to EPA and request that EPA: adopt the Reasonable Progress Alternative to BART set forth in Appendix B as the Final BART Rule;[56]The agreement contains a commitment by the current owners of NGS to cease their operation of conventional coal-fired generation at NGS no later than December 22, 2044.

[4] NGS was built with one of the first zero liquid discharge (ZLD) systems in a power plant, recovering all cooling tower blow-down and runoff from developed areas of the site.

The plant sold about 500,000 tons of fly ash per year for use in the manufacture of concrete and Flexcrete insulating block building product.

The majority owners of the NGS did not plan to keep the plant running past 2019, because natural-gas fired electricity is a cheaper nationwide trend.

[71] Plant owners and the Navajo Nation negotiated terms for a 25-year extension to the original lease that ended in December 2019.

[39]: p.IV, 106  With increased lease and royalty payments, by 2020 the plant and mine had been expected to generate more than 2,100 indirect jobs for the Navajo Nation alone, if all three units continued running.

[76]: p.23 Regional effects of installing SCR and baghouses would include increasing CAP water rates by as much as 32% for agricultural users and Indian tribes.

[39]: p.V, 68 In 2012, NGS and the Navajo Tribal Utility Authority (NTUA) formed a partnership to extend electrical power to 62 homes in the area surrounding the nearby community of LeChee.