33°8'20"S | 70°16'40"W

Los Bronces Copper Mine, Chile Overview

Scope of Work Engineering, procurement, construction, and construction management
Value $1.7 billion
Schedule 2007–2011
Business Mining & Metals

Delivering a copper mine in extreme terrain

los bronces mine

This spectacularly located and complex project traversed rugged mountainsides and elevation extremes to double copper mining capacity in the Los Bronces district for our customer, Anglo American Sur S.A. Los Bronces is some 40 miles (65 kilometers) northeast of Santiago.

Within months of their completion in late 2011, the various sites that comprise the copper concentrator expansion project had already begun to blend back into the dramatic landscape along the western face of the Chilean Andes. 

Inside the project

We carved one Los Bronces job site, Confluencia, from a tiny, steep pinnacle 2 miles (3.5 kilometers) above sea level. We tucked another into a hillside far below. To transport ore between them, we managed construction of a slurry pipeline that plunges more than 8,700 feet (2,652 meters) over rough terrain, through hard-rock tunnels, and via bridges over deep canyons.

Throughout the project, we encountered new variations on hazards we know well, including snowfalls that could bury a truck, high winds, dramatic cliffs, and significant geotechnical challenges typical of mountain work. And we progressed despite the effects of the sixth-largest earthquake ever recorded. 

Safety first

Altitude sickness, extreme weather, avalanches, and rough terrain pose constant risks for workers at high-altitude sites such as Los Bronces. In keeping with our unwavering commitment to safety and health, all workers had to pass strict medical exams; some adopted special diets to lose weight and reduce their blood pressure before they could start work.

In 2011, an independent Chilean safety agency called Los Bronces the safest of any major Chilean mining construction project in a decade.

An interesting challenge

We built the Las Tortolas flotation plant on a former military target range peppered with unexploded ordnance that required a painstaking sweep before work could begin.


We brought everything—and everyone—great distances to some of the most inhospitable places on the planet. We provisioned our men and women with shelter, food, and other requirements hauled up tortuous mountain roads, where snow could pile up to 13 feet (4 meters) high. Our winter emergency committee monitored these roads 24 hours a day for avalanches and other risks. As an extra precaution, truck drivers routinely drove practice runs without their loads prior to delivery.  ​

A reclamation system—important to water management and sustainability in this arid region in the Atacama Desert—recovers and pumps slurry water to the concentrator for reuse.

How a mine works

After processing units grind crushed ore into finer and finer particles, the material enters flotation cells in which foaming agents and injected air renders a bubbly froth. A chemical agent causes lighter mineral content to attach itself to bubbles and rise toward the surface, where it is skimmed off or otherwise captured.