Waste Recycling & Investment Recovery | Hazardous Waste | Toxic Release Inventory | Polychlorinated Biphenyls (PCB) Management | Coal Ash Management | Nuclear Waste | Remediation

Updated: April 2020

We have maintained a long commitment to pollution prevention and waste minimization. More than 30 years ago, we began a campaign to identify and minimize all forms of waste material, including solid, universal and hazardous waste. The campaign focused on reducing waste materials, using product substitution to eliminate hazardous waste and recycling waste where possible. This effort dramatically reduced the amount of waste generated through our company and led us to create a waste reduction metric that continues today.

Following the waste reduction campaign, we developed Pollution Prevention (P2) Plans for our power plants. These P2 plans are implemented and maintained by the company, and some are filed with the state environmental quality agency, as required. For nearly 10 years, we have enhanced our pollution prevention and waste minimization commitment through our ISO 14001 certified Environmental Management Systems (EMS). All our power plants maintain an ISO 14001 certified EMS that includes a company policy to reduce our environmental footprint and prevent pollution.

Waste Recycling & Investment Recovery

By managing the disposal of obsolete and surplus property, equipment and materials, we are able to recover costs while reducing our waste and environmental impact. Approximately 47% of the non-hazardous waste tracked through our Investment Recovery group was recycled last year. These efforts include diverting materials from landfills through specialized recycling streams, such as scrap metal and e-waste as well as comingled single-stream recycling of common materials. Waste is also diverted through our Forestry program, including vegetation that is removed and mulched.

Investment Recovery also helps smaller Arizona communities that lack adequate recycling services, such as Douglas, Globe and Wickenburg, recycle and recover resources. We continue to explore opportunities for increased redeployment of our equipment internally and an effort to send material out to be refurbished and resold. This opportunity will extend the life of material to new users and APS as well as keep that material out of a landfill.

Approximately $1.8 million was recovered from recycling and surplus asset sales in 2019. Many reusable materials were also donated to nonprofit organizations such as Goodwill of Arizona and Treasures for Teachers. Additionally, Investment Recovery helps with special donations for the Gila Bend Firing Range for the U.S. Air Force.

Recycling Data Table

Hazardous Waste

We have a commitment to reduce hazardous waste with a goal of limiting the generation of non-episodic hazardous waste to no more than 14.5 tons per year, based on a three-year average. This goal represents a 94% reduction from our 2001 baseline year. A three-year average is used for this target to smooth the hazardous waste generation curve so that larger, infrequent events, such as major plant outages, do not inappropriately mischaracterize the dedicated day-to-day efforts to meet our waste reduction commitments.

The 2019 routine hazardous waste generation was approximately 6 tons and the three-year average generation was 7.28 tons, which is about 50% below our hazardous waste generation target. We had two episodic events resulting in hazardous waste in 2019, one from the replacement of a selective catalytic reduction material at Yucca Power Plant, creating just over 28 tons of hazardous waste, and the other from decommissioning a large fuel tank, which entailed a lead-abatement project generating about 19 tons of paint chips.

Hazardous Waste Data Table

Toxic Release Inventory

We are required to report releases of chemicals listed in the federal Toxic Release Inventory (TRI) program to the EPA. Our reportable releases under the TRI program primarily include air emissions from power plants or coal ash disposal. APS’s TRI releases for 2018 were down 78% from 2007, primarily due to significant investments made in environmental controls for our power plants and decreased coal generation. Specifically, there was an 89% reduction in air releases from 2007 to 2018 due to our actions to reduce air emissions. The majority of these releases are captured by the plants’ pollution control equipment or contained within the coal ash by-product, which is either recycled for beneficial use or properly managed in coal ash surface impoundments and landfills. Our reporting facilities are the Four Corners Power Plant near Fruitland, NM, and the Cholla Power Plant near Joseph City, AZ.

Toxic Release Inventory Data Table

Polychlorinated Biphenyls (PCB) Management

We have a robust and effective system in place to proactively identify and manage PCB and PCB-contaminated equipment. Any equipment that contains PCBs is removed from service and disposed of properly. However, due to the size of our system and the long history of our company, there are considerable challenges to identifying which equipment contains PCBs and no historical records to enable positive identification and removal. Therefore, as with most utilities, we must instead employ a testing and verification process.

Our process sets a conservative threshold of 44 parts per million (ppm) for all our equipment. Anything over 44 ppm is classified as PCB-containing and removed from service and disposed of properly. Additionally, we employ a proactive approach that targets suspected equipment based on manufacturer name and serial numbers. For example, if a transformer comes to our service center for repair or disposal and it tests above 44 ppm for PCBs, we will cross-reference the manufacturer name and serial number to see if similar transformers are elsewhere on our grid. Those transformers will then be proactively tested and removed from service if they are above the conservative 44 ppm threshold. The PCB status of our electrical equipment is tracked in an electronic database, which is available across the company.

From 2001 to 2019, we removed 17,690 pieces of equipment from the distribution and substation systems, resulting in the disposal of more than 4 million pounds of PCB-containing material.

See the PCB Data tab in the APS Comprehensive Performance Summary.

Coal Ash Management

When coal is burned to produce electricity, it generates several by-products. One of these by-products is coal combustion residuals (CCR), generically referred to as “coal ash.” Coal ash is mainly made up of rocks, minerals and other non-combustible, natural materials mixed in with the coal when it is mined from the earth. Our two coal combustion facilities (Four Corners Power Plant in Farmington, NM, and Cholla Power Plant near Joseph City, AZ) consume about 6 million tons of coal a year, yielding approximately 1.2 million tons of coal combustion residuals annually. Much of this material can be recycled and reused in manufacturing commercial products. Each coal-fueled plant is unique in the amount and type of ash produced and how it is reused or disposed.

We manage the reuse of coal ash to help reduce our environmental footprint while adding to our bottom line. To keep our coal ash from being landfilled, we sell much of our coal ash to concrete manufacturers, who use it as an essential component for cement in the production of their products. This reduces the amount of cement that otherwise would need to be produced, significantly reducing energy consumption and contributing to a decrease in greenhouse gas emissions.

Collectively, between Four Corners and Cholla, we generated 1,231,912 tons of coal ash in 2019 and sold 718,420 tons, representing 58% of the total amount produced. The amount of coal ash sold correlates to a reduction in carbon emissions of 431,052 tons in 2019, the equivalent to removing more than 84,000 cars from the road for a year. Because of its remote location, the market for selling coal ash is limited for the Four Corners Power Plant, and therefore Four Corners sells a lower percentage of its coal ash than the Cholla Power Plant.

It should be noted that we will cease combustion of coal at the Cholla facility by mid-2025 and have immediate plans to reduce the overall number of regulated coal ash impoundments at our Cholla and Four Corners facilities starting in 2019 as described below. In the interim, we are committed to reusing coal ash residuals beneficially to the extent practical and to reducing our overall coal ash management footprint.

We have installed monitoring wells around our coal ash impoundments and continue to monitor groundwater quality in accordance with the CCR rule finalized by EPA in 2015. Additionally, we are undertaking engineering projects at Cholla and Four Corners designed to minimize the impacts associated with CCR management. Combined, these engineering projects will reduce the total number of CCR operating units from 10 to 5. In addition to closing operating units, we have other capital projects scheduled or in progress at Cholla and Four Corners focused on minimizing CCR impacts to the environment.

Coal Ash Reuse Data Table

Nuclear Waste

The Palo Verde Education Center includes a
model of dry cask storage used at the
Palo Verde Generating Station.

Nuclear waste from our Palo Verde Generating Station is managed in compliance with the Nuclear Regulatory Commission and the Institute of Nuclear Power Operations requirements. These agencies conduct regular audits, and the audit reports are reviewed by the Pinnacle West Nuclear and Operating Committee. This committee is selected by the Pinnacle West Board of Directors on at least an annual basis. The committee reports regularly to the board on overall performance of Palo Verde, including operations, safety, legal compliance, key performance indicator results and trends, and any significant incidents or events.

We have a comprehensive waste management program and training that is recognized by the Nuclear Regulatory Commission during inspections as an industry leader. Due to the sensitivity of the business and maintaining the highest level of security, our process and procedures are not for public disclosure.

NRC Team Inspection - Palo Verde Generating Station (March 2019)
NRC Security Inspection - Palo Verde Generating Station (September 2017)

All employees are required to complete training that includes classroom and computer-based courses and a practical before being able to enter the Radiological Control area. As part of the training, they are also educated to minimize what they take in the area to help in reducing radioactive waste. Employees are required to refresh their training every four years and contractors every two years. There is additional required training for all employees that handle the packaging and shipping of the waste.

Palo Verde produces high-level nuclear waste in the form of spent fuel and low-level waste, such as used protective clothing, filters, resins and other contaminated items. We safely and securely store all of Palo Verde’s high-level nuclear waste (i.e. spent fuel) on site. Palo Verde continues to move spent fuel from the spent fuel pools to dry cask storage. Dry cask storage is a safe, low-maintenance and effective interim storage method for all our high-level nuclear waste.

In addition to the on-site maintenance of spent fuel and high-level waste, Palo Verde manages its low-level waste by packaging the waste in proper containers and shipping the waste for disposal in permitted disposal facilities. Low-level radioactive waste numbers below represent waste that was shipped offsite, not what was generated for the year. Fluctuations in waste shipments are impacted by episodic events, legacy waste and what was disposed of in a given year.

Radioactive Waste Table


Prior to the development of natural gas and the widespread use of electricity, a synthetic gas made of either coal or gas was manufactured for heating and lighting purposes. This manufactured gas was commonly used in the United States beginning in the late 1800s, with as many as 1,500 facilities eventually operated across the country. Thirteen of them were located in Arizona, eight of which were operated by APS predecessor companies.

Beginning in 1987, we performed investigations to establish the extent and location of residues at former manufactured gas plant (MGP) sites. We have been working with oversight from the Arizona Department of Environmental Quality (ADEQ)’s Voluntary Remediation Program to remediate remnant MGP sites.

Preparation for the remediation involves extensive planning, developing designs and specifications, defining the extent of impacts, developing remedial strategy, community engagement, obtaining various permits and approval from ADEQ. In 2018, we completed remediation at the Grant Street site in Phoenix and obtained a “no further action” determination in 2019. In 2018, additional research and site investigation was started for the MGP sites located in Miami and Douglas, the last two MGP sites from the original eight. These sites are scheduled to be completed in 2021.

MGP site in Globe, Arizona (1904)

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