Waste Recycling and Investment Recovery | Hazardous Waste | Polychlorinated Biphenyls (PCB) Management | Coal Ash Management | Nuclear Waste | Remediation

Updated: April 2023

As stewards of Arizona, we are committed to pollution prevention and waste minimization in our daily operations. We are committed to preserving our planet through environmental stewardship by following company policies, processes and procedures for sustainability and considering the environmental impact and risk assessment of each decision we make. In addition, we comply with all environmental laws and regulations, going beyond compliance when appropriate.

More than 30 years ago, we began to identify and minimize all forms of solid waste, including universal and hazardous waste. We focused on reducing waste materials, using product substitution to eliminate hazardous waste and recycling whenever 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.

We also 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 Arizona Department of Environmental Quality (ADEQ), as required. For nearly 10 years, we have enhanced our pollution prevention and waste minimization commitment through our Environmental Management Systems (EMS). Our company maintains an EMS that includes a company policy that promotes environmental stewardship, improves our long-term planning and reduces our environmental footprint.

Waste Recycling and Investment Recovery

Our innovative Investment Recovery team looks for opportunities to reduce, reuse and recycle materials to minimize our impacts to the landfills, while also finding ways to recover costs. With more than 42 million pounds of waste per year, there are many opportunities for diversion and cost recovery. Approximately $4.3 million was recovered from recycling and surplus asset sales in 2022.

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By managing the disposal of outdated and surplus property, equipment, and materials, we can recover costs while reducing our waste and environmental impact. Approximately 55% of the non-hazardous waste tracked through our Investment Recovery group was recycled last year. Investment Recovery continues to identify and integrate new and innovative recycling and waste opportunities.

Our recycling efforts include diverting materials from landfills through specialized recycling streams, such as scrap metal and electronic recycling, 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. We also help smaller Arizona communities that lack adequate recycling services, such as Douglas, Globe, and Wickenburg, by deploying three-yard recycling bins to collect recyclable material and then using our internal hauling team to bring full bins to a centralized pickup location.

Many reusable materials were also donated to nonprofit organizations and local schools. These range from office supplies, furniture, electronics, solar panels, hand sanitizer, face masks, and appliances.

Learn about waste recycling data.


Hazardous Waste

Our goal to reduce hazardous waste is to limit the generation of non-episodic hazardous waste to less than 14.5 tons per year, based on a three-year average. This goal represents a 94% reduction from our 2001 baseline year.

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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 2022 routine hazardous waste generation was approximately 3.58 tons and the three-year average generation is 3.26 tons, which is about 77% below our hazardous waste generation target. In 2022, two events resulted in the generation of 57.2 tons of episodic hazardous waste: the first event occurred at a power plant and the second at a substation.

Learn more about our hazardous waste data.

Polychlorinated Biphenyls (PCB) Management

We have a robust and effective system in place to proactively identify and manage PCBs and PCB-contaminated equipment. Equipment identified as containing PCB 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 PCB, and in some cases, there are no historical records to enable positive identification and removal. Therefore, as with most utilities, we must instead employ a testing and verification process.

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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 learn 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 2022, we removed more than 17,910 pieces of equipment from the transmission, distribution and power generating systems, resulting in the disposal of more than four million pounds of PCB-containing equipment.

Learn more about our PCB data.

Coal Ash Management

When coal is burned to produce electricity, it generates several by-products. One of these by-products is generically referred to as “coal ash” and is considered a coal combustion residual. 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.

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Our two coal combustion facilities (Four Corners Power Plant in Fruitland, NM, and Cholla Power Plant in Joseph City, AZ) consume millions of tons of coal per year, yielding tons of coal ash. 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. Coal ash as a concrete additive fortifies concrete thereby making it stronger and last longer.

Collectively, between Four Corners and Cholla, 1,253,253 tons of coal ash were generated in 2022 with 206,960 tons sold, representing 17% of the total ash produced. The amount of coal ash sold correlates to a reduction in carbon emissions of over 124,000 tons in 2022, the equivalent of removing more than 25,000 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.

Nuclear Waste

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.

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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.

A model of dry cask storage used at the
Palo Verde Generating Station.

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 Security Inspection - Palo Verde Generating Station (October 2020)

NRC Integrated Inspection Report - Palo Verde Generating Station (February 2022)

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 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.


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 in Arizona, eight of which were operated by APS predecessor companies.

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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 (ADEQ VRP) 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 2021, APS completed the field portion of the Douglas MGP project and obtained approval to close out the project in 2022. In addition, APS obtained formal closure, no further action from ADEQ VRP for the Prescott MGP and the Phoenix 501/505 MGP sites. This effectively closes out the APS MGP legacy remediation program.


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