• CDM Smith and Golden Vertex are partnering to safely breathe new life into Arizona's historic Moss Mine.

file under: Design-Build, Environment, Industrial, Metals and Mining, North America, United States

New Life for an Old Mine

Transforming a historic site into a productive model of mining


There is gold in those hills just outside of Bullhead City, Arizona, USA, and Golden Vertex is preparing to mine millions of tonnes of ore to obtain the precious metal. The site is Moss Mine, a historic gold property in the Oatman District dating back to the Civil War, when burros and black powder were used to mine high-grade ore near the surface. Today, CDM Smith is implementing a design-build program to reactivate the idle mine, allowing Golden Vertex to dig deeper and transform the historic site into a productive model of mining.

Planning for Success
Providing turnkey “life-of-mine” services, CDM Smith is currently in the preliminary engineering and environmental permitting phase—a pivotal stage for success. “For mining projects, the very first phase is ore discovery, and companies cannot get permits or begin design until this phase is complete. These projects are made or broken by engineers’ planning and cost projections,” explains Bob Vince, CDM Smith client service manager. CDM Smith is using the firm’s regulatory and environmental expertise to secure and expedite the appropriate permits, taking advantage of regulatory provisions that will allow for immediate production.

The project also involves significant environmental controls. “We are removing materials where nature put them and placing them where humans want them, ” describes Brian Munson, CDM Smith project manager. Efforts will manage runoff from the region’s frequent monsoon rains, keep fine powder and soil in place, and use liners and leachate detection to prevent processing fluids and chemicals from being released into the environment. The project is installing all of the measures to protect the soil, water and air.

Moss Mine explorations of mineralizationBefore implementing the site's new heap leach mining system, the project team is employing best practices in scientific exploration to help define the limits of the mineralization.

A 3D Pot of Gold
CDM Smith will be implementing the project’s new heap leach mining system, where excavated raw ore will be crushed and reduced into fine pellets, stacked on a liner or leach pad, and then irrigated with sodium cyanide to separate the gold from solids. The gold-laden pregnant solution drains to a pond and is then pumped to a processing plant to recover the gold. “It is the most economical way to recover gold and we worked with their seasoned mining executives to strategize the solution,” states Vince. Initially, a pilot test of 100,000 tonnes will be conducted in advance of full-scale mining. Phase II production is expected to process 5,000 tonnes of gold ore daily, with an estimated gold and silver equivalent of 956,800 ounces, worth an estimated gross value of more than $1.5 billion.*

To optimize mining efforts on the highest grade reserves, advanced modeling software will convert raw exploration data, such as gold assays from core samples, into 3D models of the subsurface ore. “The extent of the deposit has grown using modern scientific exploration and we continue to define the limits of the mineralization using the best science practical,” states Joe Bardswich, Golden Vertex project manager. “We strive to do this as a socially responsible corporate citizen and will continue the project’s development with occupational and environmental safety as a guiding principle.”

Safety and Sustainability
The 3D model can also delineate hidden hazards such as historic underground workings. Using old mining maps and topographic laser scans result in better above- and below-ground condition analysis for site safety. Safety is so important in mining that the industry is regulated by its own government agency, the Mining Safety and Health Administration (MSHA)—a sister agency to the Occupational Safety and Health Administration. Ken Meyer, CDM Smith principal health and safety (H&S) manager and MSHA-certified trainer, is developing the mine’s H&S plans. “An effective H&S culture is paramount for mining clients. Unless you have worked on a mine, you might not recognize the potential for hazards, like heavy-duty crushing equipment, large trucks and undetonated explosives.”

To improve public safety around the mine, adits—openings in the ground—and other mining hazards will be closed. “These are fragile environments and we must ensure that what we’re leaving behind is stable and safe. We want to orient operations and develop land use toward productive post-mining, such as natural habitats and off-road recreation,” says Munson. “Often, mine hazard closures are funded by taxpayers. Golden Vertex and CDM Smith are working with state mine inspectors to safely close and reclaim the abandoned mines and historic workings at no taxpayer cost.”

Beyond benefitting the local economy, the mine’s success may serve as a model for other sites. Vince also believes that today’s approach to mining has longer term benefits. “The return to these historic properties, which were developed prior to environmental awareness, allows today’s mining companies to address past impacts with solutions that preserve the industry and environment.” For Bardswich, the ultimate measures of success are fundamental, “Zero accidents, minimal disturbance, proper reclamation and profitable operation. Very few exploration projects progress to production; we have a very good chance of becoming a profitable mining operation thanks to this project.”

*NI -43-101 estimate from Scott E. Wilson Consulting, as measured and indicated resource.