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AQD | Minerals Research, Inc. (MI) | Permit of Interest

Air | Permit of Interest for:

Minerals Research, Inc.

Revised On: May 6, 2024 - 3:50 p.m.

Facility Information

The Minerals Research, Inc. (MRI) facility processes historical copper smelter slag (i.e., waste matter remnants) to produce a variety of products, including abrasive blasting media, roofing granules, and pavement aggregate. 

MRI’s operations include drilling and explosive blasting of the slag pile, primary and secondary crushing, and screening, stockpiling of crushed slag, drying and screening, and product storage and unloading.

MRI Website | Learn More > 


705 East Birch Street
Cottonwood, AZ 86326

Air Quality Permitting

On Oct. 31, 2023, ADEQ received an Individual (Class II) Air Quality Permit Application from MRI for the operation of its Cottonwood facility and deemed the application complete on Nov. 14, 2023 (see following Background and Documents for details).

ADEQ is reviewing MRI’s application and expects to make proposed air quality permit documents available to the public for review and comment during the summer of 2024. ADEQ’s air quality permitting process for an Individual Air Quality Permit involves a comprehensive review of emissions calculations and associated air dispersion modeling and the development of a draft permit and technical supporting document. ADEQ will make these permitting documents available for public comment, and conduct both an informal community meeting and a formal public hearing for the draft air quality permit prior to making a final permit decision.

Other ADEQ Activities

ADEQ Ambient Air Quality Monitoring

At a community meeting ADEQ conducted on Dec. 13, 2023, in partnership with the City of Cottonwood, ADEQ committed to conduct ambient air quality monitoring for particulate matter and heavy metals in the vicinity of MRI’s facility. ADEQ set up ambient air quality monitoring equipment at the two locations discussed at the community meeting — the Cottonwood Kids Park and the Veterans of Foreign Wars — and trained local volunteers on how to assist ADEQ with the project. Ambient air quality monitoring commenced on Feb. 15, 2024. ADEQ will conduct air quality monitoring as long as it takes to obtain the quality data necessary to provide to the Arizona Department of Health Services (ADHS) for its planned health consultation. Data collected when MRI is not operating will represent background concentrations, and serve as a baseline to compare with ambient air quality monitoring data that ADEQ will collect when the facility is operating. Air monitoring is expected to continue through May. A summary monitoring report will be made available by the end of the summer once all data collection is complete and results are received from the lab.

ADEQ Preliminary Investigation (PI)

ADEQ has initiated a PI under our state Water Quality Assurance Revolving Fund (WQARF) program | Learn More >

The PI is focused on potential impacts to soil and groundwater associated with the slag pile located at the MRI facility and the former smelter operations in the surrounding area. In addition to reviewing available historical reports and environmental data regarding operations and activities in the area of the MRI facility, the PI includes collecting soil and groundwater samples in the field for laboratory testing. During March and April, ADEQ collected and tested soil and groundwater samples from properties and wells that allowed ADEQ access to conduct sampling. ADEQ is assessing this environmental data to determine if additional sampling is necessary to complete the PI. ADEQ anticipates that the PI, including data evaluation, will be completed by August 2024, and the final report could be made available by late summer 2024. Following completion of the PI, ADEQ will determine what, if any, additional action may be warranted. ADEQ will share all data collected for the PI with ADHS and publish the final PI report (including all data) on this webpage.


In September 2023, ADEQ issued a Notice of Violation (NOV) to MRI based on a determination that the company did not have the appropriate air quality permit for its operations. At that time, MRI was operating under a General Air Quality Permit for Crushing and Screening. The NOV required the company to submit an application for an Individual (Class II) Air Quality Permit. Due to the extensive timeframe and process for considering and reaching a decision on the new permit application required, ADEQ and MRI agreed to enter into a legally binding agreement called a Consent Order. The Consent Order was executed on Oct. 12, 2023, and specified interim, stringent operational limits and air pollution control requirements that MRI must implement at the facility to protect public health. ADEQ terminated this Consent Order on Feb. 21, 2024, revoking MRI's authorization to operate its Cottonwood facility based on certified results that showed the facility failed a performance test. This failed performance test indicated the facility was not meeting a strict emission limit condition in the Consent Order. ADEQ believed this termination effectively revoked MRI’s right to operate its facility. 

In response to ADEQ’s termination of MRI’s Consent Order, MRI served ADEQ with a lawsuit, including a request for a temporary restraining order, in Yavapai County. After evaluating its legal options to this lawsuit, ADEQ entered into a settlement agreement with MRI on Feb. 28, 2024, and revoked MRI’s coverage under the General Air Quality Permit for Crushing and Screening. Under state law (Arizona Administrative Code R18-2-510(d)), pursuant to ADEQ’s General Permit coverage revocation, MRI has the legal ability to operate its plant under the shield of its pending Individual (Class II) Air Quality Permit application that was submitted to ADEQ on Oct. 31, 2023 and subsequently deemed complete. 

MRI’s operations must be conducted in accordance with all applicable state and federal Clean Air Act requirements. ADEQ will continue to conduct required onsite inspections to ensure the facility’s operations maintain compliance.

Documents & Other Resources


  • Fact Sheet | View >
  • Air Quality Permit Application | View > 
  • Consent Order | View > 
  • Termination of Consent Order | View > 


  • Community Meeting (Dec. 13, 2023) | Watch Video >
  • Press Releases:
    • 2/21/2024 — ADEQ Terminates Minerals Research, Inc. Consent Order Revoking the Facility’s Authorization to Operate | Read More >
    • 2/28/2024 — ADEQ Terminates Minerals Research, Inc. General Air Quality Permit; Cottonwood Facility Now Authorized to Operate under Individual Permit Application |  Read More >

ADEQ Community Liaison
Ph: 928-920-1700
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