Old Dominion Mine

"Helping Historic Mine Meet Modern Regulations"

Can a historic mine in Arizona balance safety and environmental concerns with ongoing reclamation efforts?

MWH is handing this responsibility for BHP Copper at its Old Dominion Mine Site in the historic Globe-Miami mining district in east-central Arizona. The environmental project is part of BHP Copper's Property Improvement Program.

Old Dominion Mine enjoys a rich history. Underground mining at the site began in 1882 and continued until 1931. During its half-century of operation, the mine produced about 765 million pounds of copper, 89,000 ounces of gold and more than 4.5 million ounces of silver.

Today, the site is more than 1,7000 acres, and includes one slag pile, three tailings piles, four waste rock dumps, an abandoned plant site, and more than 250 abandoned mines.

Comprehensive Environmental Services

MWH is serving as the design and construction engineer for the remediation project. Our experts are providing all environmental and engineering services to BHP Copper regarding their compliance monitoring programs and closure planning efforts.

The ongoing improvements at the old mine site are designed to:

• Improve safety conditions
• Remediate and reclaim the site
• Enhance the overall appearance
• Meet regulatory guidelines

BHP Copper — with MWH's support — has been working with the Environmental Protection Agency and Arizona Department of Environmental Quality on developing a formal closure plan. The effort will meet modern environmental requirements while retaining a sense of the mine's history.

MWH's engineering design tasks include:

• Subsurface geotechnical studies
• Mine waste geochemistry studies
• Cover alternatives analysis and modeling
• Geotechnical and hydrologic analysis
• Flood plain analysis
• Revegetation studies
• Historic preservation
• Structure demolition
• Adit and shaft sealing analyses
• Regulatory negotiations

As construction manager for the project, MWH has produced a remedial construction plan (RCP) for the site, which served as the bidding document for the construction phase. This RCP included construction level drawings and engineer cost estimates. The construction activities will include:

• Regrading tailing piles and waste rock dumps
• Constructing lined diversion channels
• Developing borrow areas
• Installing a cover that resists erosion and limits infiltration
• Implementing revegetation plan.

MWH professionals are working closely with federal and state regulatory agencies and local government departments on all construction activities for the historic site.