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MWH is serving as the Program Manager for the environmental management,
remedial design, and engineering/construction management of BHP Copper’s
Old Dominion, Copper Cities, Miami Unit, Pinto Valley, and Solitude Mine
Sites located in the historic Globe-Miami mining district in Arizona.
The sites cover an area of over 13,000 acres and include slag piles and
open pits, over 2,500 acres of tailings, more than 30 waste rock dumps,
over 800 acres of heap leach dumps up to 550-feet high, an in-situ leach
caved area, two underground mines, several historic headframes and foundations,
and over 250 abandoned mines. MWH is providing environmental and engineering
services to BHP Copper with regard to their environmental compliance
monitoring programs and closure planning/implementation efforts.
The projects are in varying degrees of completion from planning and
conceptual engineering to detailed design and construction. Closure strategies
are being developed for numerous different past and present mining activities
including in-situ leaching, underground block caving and shrinkage stoping,
open pit mining, dump leaching, solution management, open pit tailings
disposal, tailings impoundment construction, and smelting. Key technical
issues for closure include acid rock drainage, slope instability, pit
dewatering, hydraulic mining of tailings, and slope erosion/sediment
transport.
Closure planning tasks include subsurface geotechnical studies, mine
waste geochemistry studies, remedial alternatives analysis and modeling,
geotechnical and hydrologic analyses, flood plain analyses, revegetation
studies, historic preservation and structure demolition studies, adit
and shaft sealing analyses, and regulatory negotiations. All closure
planning activities are implemented in close cooperation with federal,
state, and local regulatory agencies.
Construction activities commenced in September 2002 at the Old Dominion
Mine Site and involved the regrading of tailings piles, the construction
of lined diversion channels, the development of borrow areas, the placement
of an ET cover designed, and implementation of a revegetation plan.
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