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Rosemont Project: Planning for the Future


On March 8, 2019, the US Army Corps of Engineers issued a Section 404 Water Permit for Hudbay’s Rosemont copper project near Tucson, Arizona. Receipt of the permit marks a major milestone in an exceptionally thorough permitting and public review process that took place over the course of 12 years and involved 17 governmental agencies, more than 1,000 studies, and an extensive public comment period that generated more than 43,000 comments.

Upon receiving approval from the US Forest Service of Rosemont’s Mine Plan of Operations on March 21 – which reflect the positive impact the review process has had on the mine’s layout and operational plan – Hudbay can now begin developing the mine. Once fully operational in 2022, Rosemont will be the third-largest copper mine in the United States, accounting for 10% of the country’s annual copper production. Over a projected life of mine, currently estimated at 19 years, Rosemont is expected to produce approximately 127,000 tonnes of copper annually.

Rosemont’s final environmental impact statement (EIS) exceeded 2,600 pages, detailing the specific requirements necessary to mitigate the project’s impacts. The subsequent Mine Plan of Operations, at more than 4,000 pages, details the sound environmental management practices and advanced mining techniques Rosemont will operate under with respect to sustainability, notably in the areas of managing water and tailings, monitoring and mitigating environmental impacts, and making a positive and lasting contribution to communities near Rosemont.

Our goal, and our expectation, is that Rosemont will establish a new standard in the industry for how to more sustainably mine copper – a metal that is essential to sustaining and improving society.

Replacing 100% of the Water Used

Water is a precious resource in the American Southwest, and it is also essential for many mining processes. Our water management approach at Rosemont is guided by the principles of “reduce, reuse and replace”, and is expected to result in water consumption that will be among the lowest in the world per pound of copper produced.

We have voluntarily committed to replace all the water used at the operation, and, as of the end of 2018, we have already purchased and stored approximately nine years’ worth of water (around 45,000 acre-feet) in the Tucson Active Management Area Avra Valley and Lower Santa Cruz storage facilities. This water will be returned to the Rosemont-area aquifer, via recharge of the Central Arizona Project (CAP) water. Rosemont is supporting a $28 million project with Community Water Company of Green Valley to build an eight-mile pipeline and water recharge facility that will bring CAP water to the region.

Rosemont will also be a zero-discharge site, meaning the water used in processing will remain on site to be recycled and reused.

Among the initiatives and commitments related to water quality are programs to protect residential wells for those living within the vicinity of the project and those near production wells operating for Rosemont. In addition to monitoring area wells and surface water, Rosemont will carefully evaluate and manage stormwater and runoff water from our operations to minimize any adverse impacts.

Rosemont will employ numerous technologies and processes to reduce its water consumption, with one of the more innovative being the use of dry-stack tailings.

Dry-Stack Tailings – Reduces Water Consumption, Footprint and Risk

After copper-bearing ore has been mined, it goes through a series of processes – grinding, crushing and mixing with water – to separate the copper from the rest of the rock. After the copper has been extracted, what remains looks like fine mud or silt, called “tailings”.

Managing tailings in a responsible, sustainable way is a key consideration for every mine. At Rosemont, instead of conventional tailings ponds, we will use dry-stack tailings. This approach, ideally suited for a dry climate like Arizona’s, uses 50% to 60% less water than similarly sized mines, has a smaller footprint, is more stable, poses no threat to groundwater through seepage and allows for easier land reclamation and rehabilitation.

With the dry-stack method, about 85% of the water is mechanically filtered out of the tailings, leaving a material that resembles damp sand. The water extracted through this process will be reclaimed and reused for mining purposes.

Waste rock (the non–ore bearing rock) will be used to construct a buttress around the dry-stack tailings facility. Tailings are spread out on the prepared storage area, and as new tailings are generated, they are spread or stacked on existing tailings, forming an exceptionally stable bed. As this bed rises, the height of the waste rock barrier will also be increased to contain it. When mining operations cease, the dry-stack enclosure will be completely covered with waste rock and soil, and then contoured and planted so that the enclosure blends with the surrounding natural landscape.

To minimize visual impacts from the road and surrounding areas and support ongoing reclamation, the remaining waste rock will be stored behind a buttress near the facility. The barrier will be covered with soil and revegetated with plants native to the area.

Conservation Tailored for the Distinct Area

The Rosemont project will take innovative steps to preserve and protect local plant and animal populations. For example, we will conduct “camera trapping”, covering a 200-square-kilometre site with sensor-equipped cameras that are capable of capturing animal movements day and night. Images from the cameras will be reviewed regularly by a trained biologist, and the findings will be shared with Hudbay and the relevant regulatory agencies.

Habitat restoration programs for birds and aquatic animals include monitoring the range of an Arizona-specific breed of orchid and the habitat it relies on, protecting bat roosts, providing US$4.25 million in funding to agencies to create or maintain habitat on public lands nearby, and numerous other activities that contribute to species preservation and biodiversity.

For over a century, Arizona has been a favourite spot for both amateur and professional astronomers. To avoid impacts on the state’s astronomy industry while ensuring employee safety, Rosemont will implement a technologically advanced lighting system. Our lighting plan was developed in consultation with an International Dark-Sky Association board member, and features include filtered LED fixtures, colour rendering to avoid blue-spectrum lights, and shielding/beam control on non-fixed lights to reduce direct uplight.

A unique air quality measure we will employ at the site involves using equipment with tier 4 engines. Tier 4 diesel engines have the highest EPA emissions standards for off-highway vehicles, delivering a 90% reduction in particulate matter and a 50% reduction in nitrogen oxides emissions.

We will also use a wide range of innovative approaches to ensure no dust leaves the site during the construction and operation of Rosemont. Our processing equipment will feature cartridge-style dust collectors. The conveyors will be covered, and water-sprays situated along the transfer points will keep dust down. Road watering and road binders, as required, will cut down on dust generated by mine traffic. Once the mine is operational, we will also use natural gas–powered buses to transport employees to and from the mine site, which will help reduce emissions and traffic along State Route 83.

Designed to Protect the Past and the Future

Once we begin developing Rosemont, archaeologists will come to the site before any construction activities commence, and they will support the operation throughout its mine life to ensure we catalogue and manage any historically and culturally significant findings or sites on the property.

The robust permitting and public comment period for Rosemont provided us with a greater understanding of nearby communities’ priorities, and these are reflected in Rosemont’s numerous commitments to contribute to the region’s long-term economic prosperity and well-being. Examples include an annual contribution of US$500,000 to support community giving and a $25 million trust dedicated to conservation, recreation, cultural and environmental projects and education.

We highlight these features and more in a video on the Rosemont project that is available on the home page of our website at

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