The Resolution Project Mining Approach

Protecting Apache Leap

Resolution Copper is committed to preserving the cultural significance and natural beauty of Apache Leap. To do so, we have included a 695 acre easement, approximately 1,500 feet in width, as part of the land exchange legislation. (A conservation easement is a legal agreement that limits development on or use of a property or geographical feature in order to protect its associated resources.) The easement will be managed by a third party (not Resolution Copper) and will be open to the public. In addition, this easement will be extended further south to incorporate some Resolution Copper private lands.

Here are two important points to note. You’ll learn more about each by reading this section of our website:

1. Our commitment to protecting Apache Leap is absolute, and we are taking a variety of steps (described below) to ensure that the area is not harmed as a result of our mining activities. If any potential threat is determined, we will change our mining practices to ensure the Leap is protected.
2. Key components of the mine infrastructure will be located such that they will be in jeopardy from subsidence long before the Apache Leap or Queen Creek Canyon. So by protecting the integrity of our mining operation we are also protecting the Apache Leap and vice versa.

The positive aspects of a block cave mine include no overburden waste piles on surface, and no large open pits. One consequence of block cave mines, however, is the potential for surface subsidence or settling. Surface subsidence is caused as the material above the orebody gradually moves downward to replace the ore that has been mined.

The effects on the surface will vary with distance from the orebody and can be divided into a series of zones, as illustrated in the figure below.

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Using industry standard engineering practices, we are able to predict the cave, fracture and intact zones based on orebody knowledge gained during our pre-feasibility drilling work. However, the best understanding will come once mining begins.

Keeping a Close Watch on Subsidence
Mining will start at a point away from Apache Leap, This will allow us to gather technical information over a period of years to reassess the cave angles. This data will be used to ensure the Apache Leap easement is not impacted as mining progresses to the west. Methods to monitor subsidence include the following:

• Seismic Monitoring: Used to monitor cave progression by tracking the seismic energy that is released around its perimeter as it expands.
• Displacement Monitors: Installed down holes drilled from both surface and underground and used to sense any fracturing of the rock.
• Tilt Meters: Highly sensitive instruments that will be installed down short holes near the surface and will measure any tilting caused by the cave.
• GPS, Satellite Imagery and Laser Scanning: Surface-based monitoring that can be used to sense movements as small as 0.08 inches (2 mm).

The figure below is an aerial view of Apache Leap and the Resolution Copper Project area, based on current knowledge of mineralization. The figure shows the easement area, in yellow border, which will be protected during the mining operation. The other three lines depict the potential cave, fracture and intact zone boundaries (red, orange and green, respectively) after completion of mining (currently anticipated after 2050).

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This figure illustrates Resolution Copper’s current best estimate of the final effects of surface subsidence. The assumptions and methodology behind this estimate have been reviewed by a panel of independent industry experts. This panel visits Resolution Copper every six months to review the technical component of our pre-feasibility study work.

Why the mine would be affected before the Apache Leap
It is important to note that the way the mine will be constructed adds to the protection of Apache Leap. Here’s why.

A series of three shafts are required to provide fresh air to the underground workers and equipment. This will include the existing No. 9 shaft and two new shafts in the same area. These shafts will be the main lifeline to the mine and will cost in the order of $400 million to build. The mine could not operate without these shafts.

The way we plan to mine means that the intact zone would approach the boundary of the shaft complex after 15 years of mining. At that point in time the intact zone limit would still be more than 3000 feet from the boundary of the Apache Leap easement and would take another 25 years to reach the Leap’s boundary. In simple terms, if our subsidence predictions end up being inaccurate it will jeopardize the mining operation long before it affects the Apache Leap or Queen Creek Canyon.

Summary
Subsidence evaluations and predictions will be regularly updated as more geological information is gathered and more powerful predictive tools are developed. Once caving commences, a comprehensive monitoring system will be used to track the progression of the cave, validate subsidence predictions and check the suitability of the mine plan.

If you have any questions on the plans of Resolution Copper, or the protection of Apache Leap, please contact us at info@resolutioncopper.com or call our Resolution Project Information hotline at 520.689.3409.