Optimizing development drilling at Haile gold mine

At Haile gold mine in South Carolina, OceanaGold is transitioning from surface to underground mining — a shift that brings new challenges in training, workflow, and technology adoption. Haile is the only active gold mine east of the Mississippi River, and notably, 85% of the workforce is drawn from the surrounding region. While this community-first model strengthens ties to the area, it also presents a unique challenge: South Carolina does not have a long history of underground hard rock mining. That means upskilling is essential — not only to ensure productivity but also to guarantee safety and long-term success underground.

To support this transition, Hexagon partnered with OceanaGold to trial and implement the Development Optimizer system, a technology designed to improve drilling precision to reduce overbreak, underbreak, and face dishing in underground development.

The challenge

Development drilling is the foundation of all underground advancements. Operators must drill a precise pattern of blast holes to create a tunnel of specific shape and size. Deviations, whether too wide (overbreak) or too narrow (underbreak), can increase cycle times, require rework, and increase costs.

This challenge is especially pronounced in manual drilling environments, where success is heavily reliant on operator skill and training. Without consistent guidance, even experienced crews can struggle with repeatability. Inherently complex underground conditions amplify these challenges, often leading to inaccurate and inconsistent drilling. The result is poor blasting outcomes, unplanned overbreak, face dishing, and reduced advance — all of which slow development, increase haulage volumes, and inflate costs. The net effect is a lower net present value for asset owners and tighter margins for contractors.

At Haile, these issues were already surfacing. Overbreak rates averaged 16.9% prior to the trial — well above the ideal target of under 10%. Operators were using analog Sandvik DD421 and DD422i jumbos in a “bolt-bore” configuration, meaning the same rig is used for drilling, bolting, and scaling. This multi-purpose use supports flexibility and capital efficiency, but prevents the use of fixed onboard navigation sensors, which can be damaged during bolting.

Without digital guidance, drill alignment relied heavily on manual processes and operator judgment — introducing variability and reducing repeatability.

The solution: Development Optimizer System

Hexagon’s Development Optimizer is an OEM-agnostic alignment system that equips each boom with a removable, wireless sensor called the “Optibox.” Paired with a ruggedized tablet and Hexagon’s CORE Web platform, the system provides real-time alignment feedback and shift-to-shift drill performance insights. It enables operators of all experience levels to drill accurately to design — delivering more consistent blast outcomes for every cut. The result is improved fragmentation, reduced overbreak, and increased rate of advance. Importantly, it is designed to support the operational realities of bolt-bore rigs, with sensors removed prior to bolting to prevent damage.

Trial scope and results

At Haile, a structured three-week trial was conducted in late 2024 using a dedicated Sandvik DD421 jumbo. Six operators participated, each receiving in-cab coaching and working through a standardized competency checklist. Haile’s engineering team surveyed each development cut post-blast to measure overbreak and assess profile accuracy.

The following results were compelling:

• Overbreak was reduced by 35.6%, from 16.9% to 10.8%.

• Drill alignment improved, with operators consistently staying within tolerance.

• Rework and re-drills were reduced, while scaling and bolting became more predictable.

Quantifying the impact

One way to ground these improvements is in material movement. Across Haile’s three-jumbo fleet, approximately 12,000 development cuts are planned annually. By reducing overbreak from 16.9% to 10.8%, the site avoids an estimated 2,973 tonnes of excess material over the course of a year, representing roughly 225 fewer loader buckets moved annually. It is a small change in percentage but a meaningful operational impact. Less waste means reduced fuel consumption, fewer haulage cycles, and more available equipment time, resulting in faster, more efficient development overall.

Implementation and adoption

Following the trial, Haile expanded Development Optimizer across its full fleet of three jumbos. The rollout followed a hands-on training model. Hexagon’s team returned to site, spending three to five in-cab sessions with each operator. This high-touch approach prioritized face-to-face coaching over remote support, and each operator worked through a structured competency checklist to ensure confident, independent system use.

Adoption, in this context, goes beyond installation — it is about embedding the tool into daily operations until it becomes second nature.

That shift was already beginning to show underground, as is obvious from the following quotes from jumbo operators:

“I like that it stays aligned with your backsights, so I do not have to get out of the cab to make sure my booms are facing the right direction.”

“It saves time marking up when you only need one backsight. It is very useful for making sure the perimeter holes are parallel.”

“I am impressed with the precision of the sensor — after drilling a tight burn, none of the holes intersected.”

These early indicators of operator trust suggest that the system is beginning to take root. When drillers use it without prompting it and engineers begin integrating the data into planning workflows, true adoption is underway.

As with any operational change, it takes time, but the foundations at Haile are firmly in place.

Expanding the approach: Production Optimizer

While the Development Optimizer system focused on improving accuracy and repeatability during lateral advance, Haile has also taken steps to improve production drilling.

In 2024, OceanaGold implemented Production Optimizer, Hexagon’s sister solution designed for longhole drilling. The system uses a similar alignment and feedback model, tailored specifically for open stoping applications. By providing drillers with real-time collar accuracy at each hole, Production Optimizer supports tighter drilling, reduced dilution, and improved stope shape, delivering downstream benefits to fragmentation, recovery, and mill performance.

The goal is simple: straighter holes, better stope shapes, and less dilution. Improved drilling precision upstream translates into stronger fragmentation, cleaner recovery, and more predictable mill feed downstream.

Together, Development Optimizer and Production Optimizer represent a unified, system-agnostic approach to underground drilling optimization. With both systems now deployed at Haile, the site is building a digital drilling foundation — one that enhances precision, reduces rework, and supports smarter decision-making across the mine’s full development and production cycle.

Technology adoption: Lessons in change management

At Haile, adoption is still work in progress. Operator feedback has been strong, and early wins have helped build momentum, but long-term change takes time, especially in dynamic, high-turnover environments. Hexagon continues to support the site through follow-up training, product updates, and periodic on-site engagement to help embed the system into the daily development workflow.

The following lessons have emerged from this process:

• Start with buy-in: Not every operator sees the value on day one. It took one-on-one coaching and multiple in-cab sessions to build understanding of how the system supports both individual performance and the bigger operational picture.

• Build confidence through support: Real-time guidance, structured training, and a clear sign-off process gave operators the tools and confidence to trust the system and use it effectively.

• Enable long-term success: Technology alone is not enough — sustained adoption requires alignment between operators, engineers, and site leadership. When all three groups are engaged, the system becomes more than a tool — it becomes part of the culture.

Looking ahead

Following the trial, OceanaGold expanded Development Optimizer across all three jumbos at Haile. As underground mining projects in North America look to improve efficiency, reduce rework, and strengthen safety outcomes, the approach at Haile offers a strong example of how technology — paired with training and process change — can modernize drilling practices without overhauling entire fleets.

For Hexagon, this is just the beginning. New developments in automation, planning integration, and alignment analytics are already underway. But as the team emphasizes, precision starts at the collar — and the path to better mining begins with better drilling. 

Garrett Doll is the team lead of underground services & support at Hexagon’s Mining Division.