The Pinto Valley mine has found ways to conserve water in a water-stressed district. (Photo: Capstone Copper)

Ongoing projects protect and support people, the environment and cultural heritage

Capstone Copper recently published its 2022 Sustainability Report, Growing Responsibly. In it, the company, which operates the Pinto Valley mine, located in the west end of the historic Globe-Miami mining district of central Arizona, documents several initiatives that are contributing collectively to improving its sustainability. Pinto Valley contributed through its efforts to, among others, sustaining biodiversity, supporting mental health, and showing respect for cultural heritage.

A little more than a year ago, Lyndsay Potts was named general manager for the Pinto Valley mine. As the mine’s first female general manager, she brings a wealth of experience from positions she held in geotechnical services; mine management; health, safety and environment; and community relations. She and her family relocated to Arizona from Australia in November 2022.

In the report she emphasized the importance of local recruitment. “It’s about community involvement,” Potts said. “We want the community to see that we bring revenues, wages and pride. We’re not just making donations — we are members of these communities. It’s important for our growth plans that we earn the support of our communities. We also need to show we take their concerns seriously, such as their concerns about water conservation.”

Potts also discussed one of her goals, meeting the Copper Mark Criteria for Responsible Production, which is more challenging for a legacy site like Pinto Valley. “We are actively working to bring this site up to Copper Mark standards and challenging norms about what can be done with aging infrastructure,” she said. “It has people excited.”

Pinto Vally recently marked 10 years of continuous operations and they want to extend that trend with sustainable production by operating efficiently and reliably, conserving water and maintaining low turnover.

Energy Efficiency and Water Conservation

Capstone said energy efficiency is a key criterion for upgrading equipment and securing funding for new capital projects on site. For example, Pinto Valley has replaced several pieces of equipment that reached the end of life with newer, more fuel-efficient models. Some of the new equipment uses engines that exceed U.S. EPA Tier 4 regulations and provide up to 20% fuel improvement in efficiency over previous models.

The company also encourages sites to look for efficiency opportunities with energy-intensive infrastructure. In 2022, Pinto Valley completed an efficiency study of its grinding circuit, which is responsible for two thirds of the mill’s energy consumption.

All of Capstone’s mines operate in water-stressed regions with the potential for water shortages. Arizona has experienced extreme drought conditions over the last several years, leading to increased attention to water use. There are also cumulative impacts on local water resources resulting from different users competing for water in water-stressed areas.

Collaborating for the benefit of all shared interests, Pinto Valley works with and responds to communities and stakeholders who have a shared interest in the health of the Pinto Creek watershed. The mine hosts and facilitates annual meetings with Pinto Creek stakeholders to discuss the mine’s water use and the water budget of the watershed. Pinto Valley also works with the U.S. Forest Service and other stakeholders to map and monitor wells, seeps, and springs in the watershed, and funds the monitoring of U.S. Geological Survey stream gauge stations along Pinto Creek.

Pinto Valley also uses alternate tailings deposition methods to reclaim more water from its tailings storage facility (TSF) and it deploys physical and chemical inhibitors to reduce evaporation. Upgrades to the center walls of the tailings thickeners in 2021 resulted in savings of about 3,000 liters per minute due to water recovered from the thickener overflow.

Capstone has Independent Tailings Review Boards (ITRBs) comprised of external third-party technical experts who have not been involved with the design or operation of the TSF. The boards meet periodically to review and provide recommendations to improve Capstone’s tailings management. The company regularly reviews closure and post-closure costs and provisions. They engage independent experts to estimate the TSF closure and post-closure costs at each site.

Suppressing Dust in a New Way

Managing dust is a full-time preoccupation for Pinto Valley Operations Superintendent Lyn Jugler. His team works closely with the environmental department to ensure air quality permits are met. They are highly aware of the impact dust can have on nearby towns or people using the major road that passes by the mine. It’s also a workplace concern. As Jugler puts it, “Nobody wants to breathe dust all the time.”

Water trucks operate continuously to manage dust on the roads in and around the pit. However, in the heat of summer, the benefit of watering only lasts about 15 minutes. That’s why Pinto Valley was keen to try a new product made of magnesium chloride that can be mixed 1:1 with water in the water truck’s tank. The product binds fine dust particles together, preventing them from becoming airborne. This extends the time frame for rewatering by hours or even days.

Pinto Valley tested it in the summer of 2022 on some high-traffic roads and were very happy with how it performed. To make the best use of an expensive product, they apply it as a spot treatment on fixed roads, but not temporary roads deep in the pit that may only be used for a week. Jugler estimates that two thirds of their roads are being treated regularly, with benefits for those who drive the water trucks. “It makes the water truck operators’ life simpler. They’re not constantly refilling, so they can take a moment to breathe,” Jugler said.

He finds the improvement in dust suppression is very noticeable and air quality testing backs this up. For him, the evidence is there every morning. “When the sun comes up as you’re driving into the mine, the first thing you notice coming down that hill is that there isn’t a haze,” Jugler said.

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Pinto Valley uses a 1:1 ratio of magnesium chloride to water in its water trucks to suppress dust. (Photo: Capstone Copper)

Sustaining Biodiversity

The ecosystem for the Sonoran Desert, where Pinto Vally operates, is fragile due to extreme weather conditions and human development of the land. Bordered by the Tonto National Forest, it is situated in the Pinto Creek watershed. The recent completion of an Environmental Impact Statement and approval of a Mine Plan of Operations for Pinto Valley’s expansion project will bring additional monitoring and mitigation measures.

Pinto Valley actively mitigates risks of potential acid rock drainage associated with surface water runoff by encapsulating waste rock and tailings with inert materials. Alternately, they capture and recycle surface water runoff that contacts these materials in a network of catchments, ponds, and reservoirs. Groundwater quality is protected by the hydraulic capture zone created by the open pit, active pumping of downgradient water production wells, and high evaporation rates on the surface of waste dumps and tailings impoundments.

The reclamation activities planned for Pinto Valley’s mine closure (currently projected for 2039) will include landform regrading and contouring, and revegetation with native plant species. The mine has created vegetation reference plots to monitor the success of species for revegetation potential.

The mining operation also makes use of appropriate equipment and operational practices to reduce dust. Equipment solutions include wet scrubbers on conveyor belts and enclosures or covers on dust-prone areas such as conveyors, stockpiles and concentrate storage. In 2022, Pinto Valley replaced seven dust collectors with modern, efficient cartridge filter units that do not require water, unlike the old wet scrubbers.

Air quality monitoring, for both worker safety and environmental protection, ensures Pinto Valley meets regulatory standards and quickly responds to issues. All Capstone sites monitor or conduct sampling for fine particulate matter (PM), specifically PM10 and PM2.5. Pinto Valley conducts annual stack testing to ensure dust control equipment is functioning as expected. It also uses visual monitoring for dust, based on approved procedures for gauging opacity. The site records observations and uses them to activate contingency measures.

Pinto Valley submits an annual emissions inventory report to the Arizona Department of Environmental Quality (ADEQ). In addition to reporting PM emissions from all sources, they are also required to report carbon monoxide, volatile organic compounds, nitrogen oxides and sulphur oxides from stationary sources (e.g., internal combustion engines, boilers, heaters) but not from mobile equipment or vehicles.

The mine’s tank house generates hazardous air pollutants (HAP) primarily related to sulphuric acid mist from the electrowinning process. HAP emissions dropped 27% in 2022 when an updated emissions factor issued by ADEQ was applied.

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The mine realized 20 gpm in water savings by replacing old wet scrubbers with new, water-free dust collectors. (Photo: Capstone Copper)

Cleaning the Air and Saving Water

Crushing and grinding ore can generate a lot of dust. Since PM is unhealthy for people and ecosystems, it’s important to prevent it from escaping. Pinto Valley’s Mill Maintenance Superintendent Brandon Greer explained that the original dust collectors (i.e., wet scrubbers) in the Pinto Valley mill worked by ventilating dust laden air and spraying it with water to capture dust before releasing it outdoors. “The old scrubbers were essential for meeting our permits, but they were showing fatigue, and we were always doing maintenance to keep up,” he said.

Replacing the old wet scrubbers with new models that require no water was a clear win-win situation. In 2022, Pinto Valley replaced seven dust collectors with filter cartridges that contain 12 filters in each unit. After a year of operation, Greer said he was impressed with the result. “I feel like you can see the difference in emissions, and the units are much more efficient to operate,” Greer said. Performance testing of the stacks associated with the new units showed a 10-fold reduction in PM10 emissions from these seven sources.

Even more impressive to Greer are the water savings from the switch. “Each of the units we replaced ran through approximately 20 gallons per minute (gpm) of water, round the clock,” he explained. “That’s a big savings. Any way we can salvage our water resource by using it as minimally as possible, while still operating efficiently, just makes sense.” Capstone plans to replace an additional two wet scrubbers with high-efficiency cartridge filter units at Pinto Valley.

Supporting Mental Health

When nurse practitioner Jody Vines joined the Pinto Valley team six years ago, she became part of a new on-site clinic at the mine. This clinic was created to perform health checks required by the regulator, as well as injury assessments. Because it’s on site, the clinic is convenient for employees and is lower in cost.

An even bigger benefit of the on-site clinic has been the presence of a compassionate ear for any employee experiencing mental health stress. Pinto Valley offers an employee assistance plan to access counselling and rehabilitation for mental health and substance use disorders. Vines is in a position to help employees make the most of that program. “It can be frustrating to navigate the medical world,” Vines said. “I can ease that burden.”

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Pinto Valley invested 10 hours/day for six months to identify, document and recover evidence of past use for further analysis by archaeologists. (Photo: Capstone Copper).

Capstone said the COVID-19 pandemic shed light on a growing mental health crisis that affects all of its sites and communities. The counties around Pinto Valley have seen an escalation in substance abuse, opioid addiction and overdoses, with devastating consequences for people and their families. At a 24-hour operation there is an additional stress factor, Vines explained. “Shift work is not easy on people,” she said. “It takes them away from their family on evenings and weekends.”

Even though mental health issues are widespread and better understood than they were a few years ago, it’s still not easy for employees to open up about their struggles. To address that, Vines’ team partnered with Blue Cross Blue Shield to launch mental health first aid classes (the mental health equivalent of a CPR certificate). In an 8-hour class, employees develop the skills to notice and support an individual who may be experiencing a mental health or substance use concern or crisis. They also learn how to initiate uncomfortable conversations with their fellow workers.

“Whether someone is struggling personally, or having trouble at home, an expression of empathy can make all the difference,” Vines said. “Just ask: Is there anything going on that you would like to talk about? I’m willing to listen.”

Workforce Retention

Pinto Valley had a higher-than-average turnover rate due to labor shortages and changing employee expectations in the Arizona labor market, a trend it said was most noticeable in the under-30 category.

Pinto Valley signed a 4-year collective bargaining agreement in August 2022, resulting in significant improvements for employees. These include more competitive wages and benefits and improved leave practices. The new agreement also permits Pinto Valley to make future wage increases without re-opening bargaining.

Respecting Cultural Heritage

Pinto Valley’s operations overlap with parts of the Tonto National Forest. Several prehistoric peoples lived by hunting and gathering in this area. The peoples who succeeded them, including the Hohokam and Salado, practiced farming, building and trade, leaving their marks on the landscape when they left the area. Their descendants include members of the Hopi, Pima and Zuni tribes who live in the area today.

Selwyn Selina belongs to a Hopi Bear clan and maintains a strong attachment to these ancient cultures. He works as a Tribal Monitor Crew Chief for Westland Resources through a program that is giving a voice to the various tribes that need to be consulted before disturbing cultural artifacts. Pinto Valley’s plan to upgrade its TSF requires extension onto some land within the Tonto National Forest. The Tribal Monitors were engaged to help identify, document and, in some cases, recover the evidence of past use, for further analysis by archaeologists.

Working 10 hours a day for almost six months, Selina’s team discovered a variety of archaeological features, such as ancient house blocks, the foundation of a compound with many rooms, a roasting oven and even two tiny beads. The investigation and exhumation of archaeological finds is painstaking and hard on the body, but Selina finds it very meaningful. “It’s important that I’m here to see this with my own eyes, and document in my own words what was here, to pass this on to my people,” he said.

He is not troubled by the understanding that once they are done, the land will be cleared. “There’s got to be change,” he said. “People have always adapted. I believe that my connection to that area is not altered even if those things are no longer there. We still celebrate and do the ceremonies, knowing what was there.”

Selina takes satisfaction in learning more about the people who came before. “What I appreciate the most is visually understanding what they were doing here,” he says. “Why did they come here? The unknown is the fascinating part.” Selina’s perspective is now shared widely with Pinto Valley employees and contractors, and he was asked to record a video for cultural awareness.