Frequently Asked Questions

MRI is committed to partnering with the Cottonwood community and to operating our business in a way that will benefit current and future generations. Transparency, Accountability, and Communication with the communities we serve and operate in are part of our core values. It is in this spirit that we have put together these FAQs – so that everyone in our community has access to the same information. Should you have any additional questions, please reach out to We are happy to hear from you! 

What does MRI do in Cottonwood?

We manufacture industrial mineral products by upcycling materials that would otherwise be considered waste. In Cottonwood, we are upcycling the copper slag pile that has covered much of the Fairgrounds area since 1937. Once the slag is fully upcycled the site will be available for redevelopment in ways that could benefit the entire community.

What is upcycling?

Upcycling is the conversion of waste materials to something useful or valuable. Upcycling is good for the environment and good for the community because it saves natural resources, reduces waste, reduces carbon emissions, and utilizes a material that might otherwise be discarded. 

How many people does MRI employ in Cottonwood?

We currently employ 17 people in our Cottonwood operation.

How else does MRI support the Cottonwood community?

We have loved being part of the Cottonwood community and have sponsored the Annual 4th of July Fireworks since 2015. We’ve found great value in sponsoring youth and high school sports, the Verde Valley Fair Association, and have hosted gem and mineral groups on our site. We see our company as a true community partner and are always looking for ways to add value. 

Who owns MRI?

We are a family business owned by Arizona residents. 

What are MRI’s operating hours?

In keeping with our Conditional Use Permit with the City of Cottonwood, we currently operate seven days a week between 6:00am – 10:00pm with reduced hours on weekends. 

Where else does MRI operate?

The Cottonwood plant is our only current operation. Prior to opening our Cottonwood operation, our group completed the successful recovery and upcycling of a copper slag pile in Ajo, Arizona in 2015. 

What is slag?

Slag is a byproduct of ore smelting, steel-making or coal burning power generation. The slag in Cottonwood is what was left over after heating and cooling ore concentrate to recover the copper it contained. It was originally molten and was poured on the ground to cool. Slag from copper smelting can be found throughout Arizona and in many other states.

What is slag used for?

We upcycle slag by crushing the material into different granular sizes. The product is used for sandblasting steel and other surfaces, as a surfacing material for asphalt shingles and roll-roofing products, in mixtures for epoxy overlays on concrete bridge decks, as fillers for asphalt seal coat products, and as fill sand for artificial turf found on football fields, parks, and backyards. It’s the small granules raked into artificial turf after installation that help the grass “stand up.”

How is slag processed?

Recovering the slag requires controlled blasting to break up the slag enough so that we can process it. Our experienced, bonded blasting contractor performs several controlled blasts per year for us. The blasts are engineered to minimize impact to the community. After the slag is broken down into manageable sizes, we put the material into a series of machines that crush the slag into the desired size. Many of the applications for the product require a different size granule. We store and bag the product on-site to sell to our customers. The needs of the customer dictates the type of packaging material we use.

What expertise is required to work with slag?

The same hard, tough, dense characteristics that make slag products so useful also make slag challenging to process. Our group’s 50+ years of experience in slag upcycling has served us well in Cottonwood. Expertise in crushing, screening, drying, material handling, dust control and packaging is required to succeed with this type of operation. 

Does processing slag produce any waste?

We upcycle and sell 100% of the slag we recover from the Cottonwood pile, generating no slag waste. 

Why is there a slag pile in the middle of Cottonwood, Arizona?

The early history of both Cottonwood and the state of Arizona are very much the story of copper mining and smelting in the West. James W. Douglas Jr., son of the copper pioneer for whom the city of Douglas is named, founded the UVX Mining Co., opened a copper mine in Jerome, and built and operated the Clemenceau smelter from 1917-1937. UVX developed the City of Cottonwood to support the copper smelting operation. The complex Douglas built in Cottonwood is listed on America’s National Register of Historic Places. The slag pile remained virtually unchanged from the closure of the smelter in 1937 until MRI began upcycling the slag in 2015. For additional history visit:

Why should the slag be removed?

If the slag isn’t removed, it will continue to be just a slag pile. The underlying property is part of the Verde Valley Fairgrounds. Once the slag pile is removed through MRI operations, the property can be redeveloped into something more valuable for the community. We are well on our way to achieving our goal of upcycling and removing the entire pile. 

What licensing is MRI required to obtain?
We operate our business in Cottonwood under a Conditional Use Permit issued by the City of Cottonwood.

We also have operated under an Air Quality Permit administered by the AZ Department of Environmental Quality (ADEQ). From July 2018 until February 28, 2024, we operated under the Air Quality Control General Permit for Crushing and Screening Plants. ADEQ determined in late 2023 that they would like us to operate under a Class II individual permit and we are in the process of that conversion. On October 12, 2023, MRI and ADEQ entered into a Consent Order agreement that essentially served as a temporary permit while ADEQ evaluated MRI’s application for the Class II individual permit which was submitted to ADEQ on October 31, 2023. On February 21, 2024, ADEQ notified MRI that it was terminating the Consent Order and with it MRI’s authority to operate. MRI challenged that decision. On February 28, 2024 ADEQ notified MRI that it was terminating our General Air Quality Permit for Crushing and Screening, but acknowledged that we are authorized to operate our pending Individual Air Quality Permit Application that ADEQ has deemed complete until such time as ADEQ takes final action on that application.

MRI also operates with a stormwater permit under the Arizona Pollutant Discharge Elimination System Stormwater (AZPDES) Multi-Sector General Permit (MSGP) – Industrial for Non-Mining.

What training do MRI employees receive to work with slag?

Upon joining the MRI team, each plant employee completes a 10-hr OSHA Safety Training course. This is followed by additional training, including equipment operation, electrical safety, plant housekeeping and dust control. 

In compliance with our ADEQ air quality permit, our employees also participate in annual training and receive certifications in evaluating emissions and supporting compliance in our operations. 

Who regulates slag and the work done with slag?

The US Environmental Protection Agency has overall oversight for all environmental permitting and compliance in the US. EPA has delegated this authority to ADEQ. As such, MRI has obtained air quality and stormwater permits from ADEQ.

How do we know working with slag is safe?

The health and safety of our employees and protection of the environment are among MRI’s highest priorities for our Cottonwood operation. All of the employee breathing zone testing we have done has demonstrated that the air quality in our workplace is safe with results well below the Permissible Exposure Limits established by the Occupational Safety and Health Administration (OSHA), including for heavy metals. This means that per OSHA regulations, our employees can safely work at our plant all day, every day without dust masks or any other form of respiratory protection. 

Additionally, we have voluntarily run independent modeling by Trinity Consultants, a highly regarded air quality modeling consultant, that determined that even if the Cottonwood plant were to operate at levels higher than the plant has historically operated, it does not and will not result in exceedances of the National Ambient Air Quality Standards (NAAQS) and complies with all federal and Arizona air emissions standards. The NAAQS are set at a level protective of human health, including sensitive subgroups, with an ample margin of safety as determined by the EPA.

How is dust and air quality currently regulated?

Dust generation from our operation is regulated by AZ Department of Environmental Quality (ADEQ) under our air quality permit as mentioned above. ADEQ has oversight over general air quality in Yavapai County.

What measures does MRI take to control dust emissions?

We go to great lengths to minimize our impact on the community. Controlling dust emissions in accordance with our permit is another of MRI’s highest priorities. To that end we have implemented many state-of-the-art industry “best practices” such as: 

We have two large, state-of-the-art dust collectors (baghouses) that provide suction to pull dust from potential emission points in our processing plant. 

We use water sprays to control dust in the slag handling portion of our operation.

We wet the slag piles with sprinklers to minimize wind-blown dust. 

We have a mobile water cannon that creates a water fog and can be moved to anywhere additional dust control is needed depending on weather conditions. 

We use water trucks to wet all roadways on site to minimize dust from vehicular traffic.

○ We will continue to take appropriate steps to maintain our facility and air pollution controls as a responsible member of the Cottonwood community.


How can I learn more about MRI and what is happening at the plant?

Please send us an email at and we would be glad to add you to our list for community events, notification for scheduled blasts, and for employment and job openings.