Cholla Generating Station

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Cholla Generating Station is a 425.9-megawatt (MW) coal-fired power station operated by Arizona Public Service Company near Joseph City, Arizona.


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Plant Data

  • Owner: Unit 1-3: Arizona Public Service Company Unit 4: PacifiCorp
  • Parent Company: Pinnacle West Capital (APS), MidAmerican Energy (Pacificorp)
  • Plant Nameplate Capacity: 1,128.8 MW (Megawatts)
  • Units and In-Service Dates: Unit 1: 113.6 MW (1962), Unit 2: 288.9 MW (1978), Unit 3: 312.3 MW (1980), Unit 4: 414.0 MW (1981)
  • Location: 4801 Frontage Rd., Joseph City, AZ 86032
  • GPS Coordinates: 34.941503, -110.301074
  • Technology: Subcritical
  • Coal type: Sub Bituminous
  • Coal Consumption:
  • Coal Source: El Segundo mine (Peabody Coal)[1]
  • Number of Employees:
  • Unit Retirements: Unit 2 retired in October 2015.[2] Unit 4 retired in December 2020.[3] Units 1 and 3 are scheduled for retirement before the end of 2025.[2]

Unit Closures

Unit 2 was closed in October 2015.[4][5]

Unit 4 retired in 2020.[6][7][8]

Units 1 and 3 are scheduled for retirement in 2025.[2]

Biomass Conversion

In March 2019 it was reported that the Arizona Public Service (APS) has begun evaluating the possibility of converting unit 1 at the plant to burn biomass instead of coal to ensure future power deliveries but regulators at the Arizona Corporation Commission voted the plans down in 2019.[8][9][10]

Emissions Data

  • 2006 CO2 Emissions: 8,526,274 tons
  • 2006 SO2 Emissions: 21,147 tons
  • 2006 SO2 Emissions per MWh:
  • 2006 NOx Emissions: 14,735 tons
  • 2005 Mercury Emissions: 259 lb.

Coal Waste Sites

Death and disease attributable to fine particle pollution from Cholla

In 2010, Abt Associates issued a study commissioned by the Clean Air Task Force, a nonprofit research and advocacy organization, quantifying the deaths and other health effects attributable to fine particle pollution from coal-fired power plants.[11] Fine particle pollution consists of a complex mixture of soot, heavy metals, sulfur dioxide, and nitrogen oxides. Among these particles, the most dangerous are those less than 2.5 microns in diameter, which are so tiny that they can evade the lung's natural defenses, enter the bloodstream, and be transported to vital organs. Impacts are especially severe among the elderly, children, and those with respiratory disease. The study found that over 13,000 deaths and tens of thousands of cases of chronic bronchitis, acute bronchitis, asthma, congestive heart failure, acute myocardial infarction, dysrhythmia, ischemic heart disease, chronic lung disease, and pneumonia each year are attributable to fine particle pollution from U.S. coal plant emissions. These deaths and illnesses are major examples of coal's external costs, i.e. uncompensated harms inflicted upon the public at large. Low-income and minority populations are disproportionately impacted as well, due to the tendency of companies to avoid locating power plants upwind of affluent communities. To monetize the health impact of fine particle pollution from each coal plant, Abt assigned a value of $7,300,000 to each 2010 mortality, based on a range of government and private studies. Valuations of illnesses ranged from $52 for an asthma episode to $440,000 for a case of chronic bronchitis.[12]

Table 1: Death and disease attributable to fine particle pollution from Cholla Generating Station

Type of Impact Annual Incidence Valuation
Deaths 25 $180,000,000
Heart attacks 39 $4,200,000
Asthma attacks 460 $24,000
Hospital admissions 18 $420,000
Chronic bronchitis 16 $7,200,000
Asthma ER visits 23 $8,000

Source: "Find Your Risk from Power Plant Pollution," Clean Air Task Force interactive table, accessed March 2011

CCS Testing

On March 25, 2009, the U.S. EPA approved carbon sequestration testing at the Cholla Generating Station. Carbon dioxide will be pumped into wells beneath the plant in an effort to determine if it can be contained.[13]

Cholla ranked 8th on list of most polluting power plants in terms of coal waste

In January 2009, Sue Sturgis of the Institute of Southern Studies compiled a list of the 100 most polluting coal plants in the United States in terms of coal combustion waste (CCW) stored in surface impoundments like the one involved in the TVA Kingston Fossil Plant coal ash spill.[14] The data came from the EPA's Toxics Release Inventory (TRI) for 2006, the most recent year available.[15]

Cholla Generating Station ranked number 8 on the list, with 2,863,427 pounds of coal combustion waste released to surface impoundments in 2006.[14]

"High Hazard" Surface Impoundments

Two of Cholla Generating Station's coal ash surface impoundments are on the EPA's official June 2009 list of Coal Combustion Residue (CCR) Surface Impoundments with High Hazard Potential Ratings. The rating applies to sites at which a dam failure would most likely cause loss of human life, but does not assess of the likelihood of such an event.[16]

Articles and Resources


  1. "EIA 923 March 2020" EIA 923 2020.
  2. 2.0 2.1 2.2 "Preliminary Monthly Electric Generator Inventory", 860m March 2020
  3. Roth, Sammy (2020-12-24). "The coal industry comes tumbling down in the American West". Los Angeles Times. Retrieved 2021-01-14.
  4. "Between 2013 and 2015, APS retired 1,030 MW of fossil fueled capacity," Pennwell Hub, June 1, 2016
  5. "Unit 2 At Cholla Power Plant Will Be Retired On October 1," AZ Journal, Sep 22, 2015
  6. Roth, Sammy (2020-12-24). "The coal industry comes tumbling down in the American West". Los Angeles Times. Retrieved 2021-01-14.
  7. Pacificorp 2017 Integrated Resource Plan Pacificorp, May 1, 2018
  8. 8.0 8.1 "Arizona coal generator to close in 2020, while another given lifeline as decline of plants across West continues,", January 7, 2020
  9. "Cholla Power Plant may get a partial reprieve from closure" March 30, 2019
  10. "APS: Biomass conversion at Cholla coal plant could cost $115/MWh,", May 21, 2019
  11. "The Toll from Coal: An Updated Assessment of Death and Disease from America's Dirtiest Energy Source," Clean Air Task Force, September 2010.
  12. "Technical Support Document for the Powerplant Impact Estimator Software Tool," Prepared for the Clean Air Task Force by Abt Associates, July 2010
  13. "EPA OKs carbon sequestration test in Ariz.", KSWT 13 News, March 25, 2009.
  14. 14.0 14.1 Sue Sturgis, "Coal's ticking timebomb: Could disaster strike a coal ash dump near you?," Institute for Southern Studies, January 4, 2009.
  15. TRI Explorer, EPA, accessed January 2009.
  16. Coal waste

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