|
|
On behalf of the Rio Tinto Working Group (RTWG), MWH is providing turnkey
engineering, environmental, public relations, construction management,
and operations and maintenance services for remediation and reclamation
of the abandoned Rio Tinto Mine. The site has been inactive for over
20 years and consists of a large underground copper mine and associated
surface disturbance (approximately 500 acres in total).
The RTWG was formed in the early 1990's to proactively address environmental
concerns presented by the U.S. Environmental Protection Agency, State
of Nevada, the U.S. Forest Service, the Shoshone-Paiute tribes, and local
residents. An Administrative Order on Consent (AOC) to voluntarily clean-up
the Rio Tinto Mine was executed between the RTWG and State of Nevada
to prevent the property from being listed on the National Priority List
as a Superfund site. MWH was retained by the RTWG to help negotiate and
implement the components of the AOC. The specific components of our scope
of work include:
- Field reconnaissance and site characterization (including field
mapping; installation of a site-wide water monitoring network with
surface water
sampling stations, piezometers and groundwater monitoring wells; surface
and subsurface soil sampling; and laboratory testing of all sampled
media)
- Stability evaluation of four potentially unstable tailings embankments
- A
hydrologic evaluation of the mine site drainage basin to determine
design flows and erosion protection measures for Mill Creek, which
drains through the property
- Preparation of final design drawings and
specifications for remediation of surface water quality impacts
- Engineering,
procurement, and construction management services for implementation
of all work at the site
- Submittal of as-built drawings and completion
reports to the Nevada Department of Environmental Protection
- Construction
quality assurance services to verify completion of all remedial elements
- O&M
of seepage control and collection system, as well as passive water
treatment systems
- Development of project-wide health and safety plan
- Coordination of
public relations and outreach activities with all stakeholders
- Post
remediation monitoring.
Specific sites reclaimed included four valley tailings impoundments
covering approximately 30 acres; a 5-acre sludge pond; mill facilities
including crushers, thickeners, mine shafts, and leaching tanks; two
hillside tailings impoundments covering approximately 6 acres; various
waste rock piles; a heap leach pad, and an onsite landfill. The primary
objective of the remediation was to address surface water impacts to
Mill Creek and the Owyhee River through a series of source control and
passive water treatment measures.
|
