Mohave Power Station
| Company type | Joint venture |
|---|---|
| Industry | Electricity generation |
| Founded | 1971 |
| Defunct | 2005 |
| Fate | Permanently closed and dismantled |
| Headquarters | Laughlin , United States |
Area served | Nevada, California |
| Products | Electricity |
| Owner | Southern California Edison (56%), Salt River Project (20%), Nevada Power (14%), Los Angeles Department of Water and Power (10%) |
Number of employees | Approximately 300 (at closure) |
Mohave Power Station—also referred to as Mohave Generating Station or MOGS—was a coal-powered electricity generation facility with a capacity of 1,580 megawatts electric (MWe) located in Laughlin, Nevada. Primarily owned and managed by Southern California Edison, it commenced commercial production in 1971. The plant ceased operations in 2005 and was subsequently dismantled.
Design
The station consisted of two generating units, each producing 790 MWe, with operational output ranging from 350 to 750 MWe under normal conditions. Between 1990 and 1998, it maintained a capacity factor of 71.5%. The boilers were manufactured by Combustion Engineering, while General Electric supplied the turbine-generators. Bechtel was responsible for the engineering, procurement, and construction phases.
Situated on a 2,500-acre plot within the Mojave Desert near the Colorado River, the facility utilized supercritical boilers paired with cross-compound steam turbines. Ownership stakes were held by Southern California Edison (56%), Salt River Project (20%), Nevada Power (14%), and LADWP (10%).
Distinctively, Mohave was the only U.S. coal plant to receive fuel via an 18-inch slurry pipeline—the Black Mesa Pipeline—stretching 275 miles from Peabody Energy’s Black Mesa Mine in Kayenta, Arizona. This pipeline could transport up to 660 short tons of coal slurry per hour. The coal slurry was stored in four tanks and eight Marcona ponds, ensuring a supply that could last up to 40 days. Water separation from the coal was achieved through centrifuges, removing approximately 75% of water prior to pulverization. The facility operated 20 pulverizers capable of processing as much as 90,400 pounds of coal per hour each. All wastewater generated was recycled on-site, rendering Mohave a zero-liquid discharge plant.
At full load, daily coal consumption reached nearly 16,000 short tons. Ash residues consisted of bottom ash and fly ash; roughly 70% of fly ash was marketed as an additive for concrete production. Each year, about 160,000 cubic yards of bottom ash and an additional 60,000 cubic yards of sludge were deposited at the Ash Canyon landfill, which spanned around 360 acres.
Startup heat was provided by a 20-inch natural gas pipeline; however, this supply alone was insufficient for full plant operation on gas fuel. Electrical power was transmitted through two 500 kV lines connecting to substations located in southern Nevada and southern California.
Commissioning
The two identical generating units began their initial operations in 1971.
Early failures
Prior to 1975, the facility encountered two turbine-generator breakdowns during periods of unusually cold weather. As a joint owner, the Los Angeles Department of Water and Power (LADWP) conducted investigations employing computer modeling of the power station along with its associated 500 kV transmission networks serving California and Nevada.
These failures were traced back to the then-new "series compensation" technology—capacitors installed in series on transmission lines intended to reduce losses typical in long-distance AC power delivery. Simulation studies demonstrated that under near-freezing temperatures, the combination of series resistance in ACSR transmission conductors with series compensation could induce a negative impedance effect impacting generators. This phenomenon resulted in mechanical stresses severe enough to destroy turbine-generators.
The problem had not been anticipated because earlier simulations concentrated on steady-state system performance rather than transient dynamic responses. These incidents led to increased focus on dynamic system modeling during power system design.
General Electric, which manufactured the turbine-generators, refused further repairs after replacing the failed units twice since the underlying cause was unrelated to their equipment quality. The plant adopted revised operational protocols that effectively prevented recurrence of this failure mode. Nevertheless, these new procedures did not resolve subsequent issues stemming from incorrect handling of the steam generator’s superheat and reheat systems—vital elements within the compound turbine-generator arrangement combining high-pressure and low-pressure sections fed by separate loops from a single steam generator.
1985 steam pipe rupture catastrophe
At 3:25 p.m. on June 9, 1985, a 30-inch hot reheat steam pipe operating at 600 psi burst. This pipe circulated exhaust steam from the high-pressure turbine back to the boiler for reheating prior to entering the low-pressure turbine. The release of steam at approximately 1000°F resulted in fatal burns to six employees and injuries to ten others. An initial inquiry pinpointed a defective weld as the immediate cause. Around 35 personnel were present on-site, including 20 stationed in the control room.
Operations halted for six months to facilitate the replacement of all steam piping.
A comprehensive accident analysis completed in May 1991 was withheld until Christmas Day due to Edison’s concerns about potential civil lawsuits. The report determined that Edison’s management decisions—or lack thereof—were "primary and critical contributors" to the failure:
- The plant was operated above its design temperature limits for prolonged durations, with operators unable to regulate temperatures because of a design defect.
- The compromised pipe underwent neither regular maintenance nor inspections despite experiencing distortion and shifting from abnormal stress conditions.
- Safety was subordinated to production priorities; in 1979, Edison reprimanded a supervisor who authorized an unsanctioned pipe weld inspection. The report criticized this organizational culture, noting it weakened safety protocols and heightened the risk of future accidents.
No direct link was found between specific actions on the day of the rupture and the incident itself.
The report recommended sweeping policy reforms, mandatory annual safety training, and rigorous inspection and maintenance reporting to the Public Utilities Commission. Since the accident was preventable, it argued that financial responsibility should fall on Edison’s shareholders rather than consumers.
Closure
The facility permanently ceased operations on December 31, 2005, with no intentions of reopening. This shutdown also terminated coal mining activities on lands owned by the Navajo and Hopi tribes, negatively impacting the Hopi community. The closure fulfilled terms of a 1998 Clean Air Act lawsuit settlement targeting the plant as a significant pollution source near the Grand Canyon. Furthermore, agreements with both tribes prohibited using local aquifer water for slurry processes. Alternatives considered included selling the plant, converting it to natural gas—which would have necessitated expensive infrastructure upgrades—or installing exhaust scrubbers costing approximately $1 billion. By May 2007, Southern California Edison (SCE) abandoned plans either to restart or sell the facility.
Decommissioning
On June 10, 2009, SCE announced its intention to fully decommission and dismantle all generating equipment. Administrative buildings were demolished as well, leaving only the 500 kV switchyard active to support regional power transmission and supply a nearby Nevada Power substation. Dismantling commenced in October 2009, with an anticipated duration of two years and an estimated cost of $30 million. Approximately 300 workers were laid off following closure.
The signature 500-foot exhaust stack was brought down using explosives on March 11, 2011. In October 2016, the entire site was placed on the market, marking the final divestiture of the former Mohave Generating Station property.
Owners
- Southern California Edison holds a 56% stake
- Salt River Project owns 20%
- Nevada Power Company possesses 14%
- Los Angeles Department of Water and Power maintains a 10% share