The 2.25GW Navajo Generating Station (NGS), the biggest coal-fired power station in the western US, is located in Navajo Nation near Page, Arizona. The plant is being decommissioned after operating for more than 45 years.

Operated by Salt River Project (SRP), a community-based non-profit public power utility based in Arizona, the three-unit Navajo power station had been in operations since 1974.

SRP owns 42.9% stake in the project, while the other co-owners are the US Department of Reclamation (24.3%), the Arizona Public Service Company (14%), Nevada Energy (11.3%), and Tuscon Electric Power (7.5%).

One of the three coal-fired units of the Navajo Generating Station was closed down in September 2019, while the remaining two units were permanently closed in November 2019.

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The decommissioning of the coal-fired power station is set to begin in 2020 and scheduled to be concluded by the end of 2023.

NGS decommissioning background

The US Department of Reclamation and the US Bureau of Indian Affairs approved an extension lease for the coal-fired power station to continue operating until December 2019, following an environmental review completed in November 2017.

The owners of the Navajo Generating Station decided not to seek further lease extension for the plant beyond December 2019.

The reasons for the unanimous decision for the permanent plant closure included the pollution allegations by the environmental groups, tightened environmental restrictions on coal-fired power plants, as well as the weakening economics for coal-based power generation on the face of stiff competition from natural gas as a cheaper option.

Navajo power station decommissioning details

The NGS decommissioning will start with the removal of the railroad catenary system that was used for coal procurement to the site, followed by the demolition of the power block and the closure of storage ponds and ash landfill.

The site restoration is expected to be achieved by 2023, following which post-closure monitoring is expected to continue for 30 years.

More than 90% of the decommissioned plant components are planned to be recycled. The plant assets that are to be either recovered or resold include 141 transformers, 1,900 tonnes (t) of copper, 105,000t of steel, and approximately 650,000 gallons of diesel fuel.

SRP had offered to accommodate all the 433 permanent employees of the NGS, out of which 284 will be rehired for the utility’s other operations.

Navajo Generating Station details

The Navajo power station was developed on a 1,020-acre site with an estimated investment of £540m ($692m) as part of the Central Arizona Project (CAP). The CAP was authorised in 1968 for building a 541km-long diversion canal for delivering the Colorado River water to the south and central Arizona.

The three coal-fired units, each comprising a boiler and a GE steam turbine generator, were commissioned in 1974, 1975 and 1976, respectively.

The other infrastructure facilities for the power station included a dedicated railroad for coal supply, a coal handling facility, a water supply system from Lake Powell, a water treatment facility, and a 500kV switchyard.

The electricity generated by the power station was being transmitted through two 500kV transmission lines connecting substations near Las Vegas, Nevada, and Phoenix, Arizona.

An estimated £360m ($465m) was spent for environmental upgrades at the Navajo power station that included the installation of flue gas desulphurisation (FGD) systems on all three generating units between 1997 and 1999.

Coal supply from the Kayenta mine

The coal supply for the power station was facilitated by the 126km-long dedicated Black Mesa and Lake Powell electric railroad connecting the NGS site with the Kayenta coal mine.

Owned and operated by Peabody Western Coal Company (PWCC), the 400-acre Kayenta coal mine was also developed as part of the Central Arizona Project for exclusive coal supply to the Navajo power station.

The Kayenta mine was closed after supplying the final shipment of coal for the Navajo Generating Station in August 2019.

Contractors involved in the Navajo Generating Station decommissioning

Independence Excavating, an Ohio-based construction company specialised in excavation and site development, has been contracted for the power block decommissioning works for the Navajo power station.

National Salvage & Service Corporation, an Indiana-based company specialised in demolition and waste management services, has been engaged for the removal of catenary poles, electrical wires, supports, brackets, and support poles along the existing coal-supply railroad tracks for the power station.