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

Updated: March 2021

We have maintained a lengthy commitment to pollution prevention and waste minimization. More than 30 years ago, we began a campaign to identify and minimize all forms of solid waste, including universal and hazardous waste. The campaign focused on reducing waste materials, using product substitution to eliminate hazardous waste and recycling more waste when 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 Environmental Management Systems (EMS). All of our power plants maintain an 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 recover costs while reducing our waste and environmental impact. Approximately 31% of the non-hazardous waste tracked through our Investment Recovery group was recycled in 2020. While this number declined from 2019, the main driver is an efficiency gain at one of our ZLD (Zero Liquid Discharge) facilities which subsequently leads to a higher volume of Metallic Salts/Oxides waste.

Our recycling 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, Casa Grande and Wickenburg. We continue to explore opportunities for increased internal redeployment of our equipment. We send material to be refurbished and resold when possible. This effort extends the life of material to new users and APS, as well as keeps that material out of a landfill.

Approximately $1.65 million was recovered from recycling and surplus asset sales in 2020. Many reusable materials were also donated to nonprofit organizations and local schools. Additionally, Investment Recovery worked with our Facilities team to pilot centralized trash at our corporate office with the goal to expand throughout the company. In 2021, Investment Recovery will explore, pilot and implement a solution to address the wooden reels currently sent to landfill.

Learn more about our waste recycling data on our ESG Reporting Page.




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 and decommissioning, do not inappropriately mischaracterize the dedicated day-to-day efforts to meet our waste reduction commitments. 

The 2020 routine hazardous waste generation was approximately 2.3 tons and the three-year average generation is 5.2 tons, which is about 64% below our hazardous waste generation target. We had two episodic events resulting in hazardous waste in 2020, one from the decommissioning at Ocotillo Power Plant, creating 3.5 tons of hazardous waste, and the other from an underground storage tank at Evans Churchill Substation that contained about 300 gallons of liquid, which created 1.6 tons of waste removed.

Learn more about our hazardous waste data on our ESG Reporting page

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, water releases, and coal ash disposal. APS’s TRI releases for 2019 were down 80% from 2008, primarily due to significant investments made in environmental controls for our power plants and decreased coal generation. Specifically, there was a 93% reduction in air releases from 2008 to 2019 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, N.M., and the Cholla Power Plant near Joseph City, Arizona.

Learn more about our TRI data on our ESG Reporting page

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 lengthy 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 of 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 2020, we removed over 17,770 pieces of equipment from the distribution and substation systems, resulting in the disposal of more than four million pounds of PCB-containing material.

Learn more about our PCB data on our ESG Reporting page

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, naturally occurring materials within the coal when it is mined from the earth. Our two coal combustion facilities (Four Corners Power Plant in Fruitland, N.M., and Cholla Power Plant in Joseph City, Arizona) consume about millions of tons of coal a year, yielding tons of coal ash annually. Much of this material can be recycled and reused in manufacturing commercial products. The coal ash is beneficially used, which reduces our environmental footprint while adding to our bottom line. Our coal ash is provided 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, 1,158,385 tons of coal ash were generated in 2020 with 583,616 tons sold, representing 50% of the total ash produced. The amount of coal ash sold correlates to a reduction in carbon emissions of over 350,000 tons in 2020, the equivalent of removing more than 68,000 cars from the road for a year. The Cholla facility will cease combustion of coal by mid-2025. Our ash impoundments and landfills are operated and maintained in accordance with the federal Coal Combustion Residual (CCR) regulations. Additionally, we are undertaking several engineering projects designed to minimize environmental impacts associated with CCR management.

Learn more about our coal ash data on our ESG Reporting page

Nuclear Waste

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 (October 2020)


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 into 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 employees who handle the packaging and shipping of 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. In 2020, Palo Verde implemented the MAGNASTOR dry cask storage system as an upgrade from the previously utilized NAC-UMS dry cask storage. This allows Palo Verde to more efficiently store high-level nuclear waste utilizing updated technology that is being adopted by other sites across the industry. Dry cask storage is a safe, low-maintenance and effective interim storage method for all of 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 it into proper containers and shipping it for disposal in permitted disposal facilities. Low-level radioactive waste represents waste that was shipped off-site, not what was generated for the year. Fluctuations in waste shipments are impacted by episodic events, legacy waste and what was disposed of each year.

Learn more about our nuclear waste data on our ESG Reporting page


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 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’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 2020, we completed remediation at the Miami, Arizona site and obtained a “no further action” determination in 2020. In 2019, additional research and site investigation was started for the MGP site located in Douglas, Arizona, the last MGP site from the original eight. This site is scheduled to be completed in 2021. In addition, in 2020 we remediated MGP residual contamination located beneath a recently deactivated substation located in Prescott, Arizona. This material was previously inaccessible. 



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