Garnet Mine Area Reclamation Project
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Garnet Mine Area Reclamation Project Final Engineering Evaluation/Cost Analysis Public Meeting – March 3, 2010. Montana Department of Environmental Quality Mine Waste Cleanup Bureau. Project Location.

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Montana department of environmental quality mine waste cleanup bureau

Garnet Mine Area Reclamation ProjectFinal Engineering Evaluation/Cost AnalysisPublic Meeting – March 3, 2010

Montana Department of Environmental Quality

Mine Waste Cleanup Bureau

Project location
Project Location

  • Located approximately 2.5 miles southwest of Pony, Montana in the Mineral Hill (Pony) Mining District of Madison County.


Garnet Mine

Mining history
Mining History

  • Mining

    • Garnet Mine began underground operations mining gold, silver, copper and lead in the late 1800s.

    • Most production occurred between 1897 and 1909 and continued intermittently through the 1930s.

  • Milling

    • Initial milling was conducted using a 20-stamp amalgamation mill.

    • Later used conventional floatation mill and tailings facility to produce concentrate for shipping.

  • Production Estimate –

    • 175,000 tons of ore

Garnet area mine features
Garnet Area Mine Features

  • Adits, some caved

  • Waste Rock Piles

  • Shafts and Collapsed Stopes

  • Valley Fill Tailings

  • Other Hazardous and Non-Hazardous Materials from Past Mining and Milling

Purpose and objectives
Purpose and Objectives

Purpose –

Prepare a functional guide for conducting reclamation activities that to the extent possible mitigate human health and environmental risks.

Objectives –

To screen, develop and evaluate potential response alternatives that would be used to clean up site mine waste.

Waste rock characteristics1
Waste Rock Characteristics

Mine Waste Rock Investigation

  • Acid-Base Accounting (ABA) – determine potential to generate acidic leachate

  • Metal Mobility – evaluate potential to release metals in concentrations exceeding DEQ surface water standards

  • Volume Survey – determine total volume of each waste pile

Waste rock characteristics acid base accounting1
Waste Rock Characteristics - Acid-Base Accounting

ABA Results Summary

  • Uncertain acid generation potential indicated by NNP (values between +20 and -20 CaCo3/kiloton of rock)

  • 3 Samples have somewhat greater potential to generate acid based on NP:AP (values below 1)

Waste rock characteristics metal mobility summary
Waste Rock Characteristics – Metal Mobility Summary

Metal Mobility Summary

  • All six waste rock samples exceeded DEQ-7 acute aquatic life, chronic aquatic life, and/or human health standards for surface water for at least one metal.

  • Pb was most common metal detected constituent

  • Cu exceeded acute aquatic life standards in five of six samples

  • Standards for As, Cd, Hg, or Zn were exceeded in three or fewer samples

Tailings characteristics1
Tailings Characteristics

Floodplain Tailings Investigation

  • Test pits were excavated throughout the tailings deposit

  • Excavated test pits were sampled at 1ft. Intervals below ground surface

  • Samples were analyzed using and X-ray Fluorescence (XRF) instrument and compared to background soil samples

Eroded tailings dam cascade creek
Eroded Tailings Dam – Cascade Creek

Assumed Original Top of Dam

Estimated Height 8’-10’

Oriole adit workings 1 095 feet
Oriole Adit Workings (1,095 feet)

Malachite (Cu) precipitate

from Jackleg Drill Holes

Oriole adit plan map
Oriole Adit Plan Map

Oriole Adit Seepage

Flow 2.2 – 7.1 gpm

Human health recreational use risk assessment
Human Health Recreational Use Risk Assessment

No Human Health affects from tailings, waste rock or surface water (excluding the Oriole Adit seepage) for any of the following recreational uses

  • Soil Ingestion

  • Dust inhalation

  • Water Ingestion

  • Fish Ingestion

Development and screening or reclamation alternatives
Development and Screening or Reclamation Alternatives

Purpose – Identify and screen technology types and process options

  • Eliminate technologies that are obviously unfeasible or ineffective

  • Retain potentially effective options

    General Response Actions

  • No Action – no further response or monitoring

  • Institutional Controls – restrict or control access

  • Engineering Controls –reduce or eliminate the contaminant

  • Excavation and Treatment – removal and subsequent treatment of contaminant

  • In-Situ Treatment – treat in place, reducing mobility and toxicity of contaminant

No action
No Action

  • No Action is generally used as a baseline against which other response options are compared

Institutional controls
Institutional Controls

  • Land use restrictions would limit the possible future uses of the land at the site

    • Mine portal closures

    • Fencing and gates

    • Area closures

  • Institutional Controls do not meet clean-up goal

  • Does not address long term public safety

Engineering controls
Engineering Controls

Engineering Controls typically include containment, capping, run-on/run-off controls, revegetation and/or disposal

  • Underground Flow Control – eliminate, minimize, or divert contaminated water flows for entering or leaving underground mine workings

  • Containment – eliminate direct contact and fugitive releases of contaminated materials

  • Surface Controls – minimize contaminate release and migration

  • On-Site Disposal – placement of contaminate in an engineered on-site repository

  • Off-Site Disposal – transporting contaminate to an engineered off-site repository permitted to accept such materials

Excavation and treatment
Excavation and Treatment

Excavation and Treatment involves the removal of the contaminated materials and subsequent treatment to reduce toxicity and/or volume

  • Reprocessing– transporting contaminate to existing mill or smelter for processing and recovery of valuable metals

  • Fixation/Stabilization – chemically alter the contaminant to reduce its mobility or toxicity or encapsulating contaminant in inert material

  • Physical/Chemical Treatment – use of physical chemical processes to concentrate constituents into a smaller volume for disposal or further treatment

In situ treatment
In-Situ Treatment

In-Situ Treatment involves treating contaminate in place with the objective of reducing mobility and toxicity of problem constituents.

  • Physical/Chemical Treatment – used to create a chemical or physical change in the mobility and/or toxicity of the contaminants

  • Thermal Treatment – used to melt contaminated solid media in place to immobilize metals into a glass-like, inert, non-leachable solid matrix

Detailed analysis of alternatives
Detailed Analysis of Alternatives

Response Action Alternative Evaluation

1. Effectiveness

2. Implementability

3. Cost

Detailed analysis of alternatives1
Detailed Analysis of Alternatives

Effectiveness –

  • Overall protection of human health and the environment

  • Compliance with the ARARs

  • Long-tem effectiveness and performance

  • Reduction of toxicity, mobility, or volume through treatment

  • Short-term effectiveness

Detailed analysis of alternatives2
Detailed Analysis of Alternatives

Implementability –

  • Address the technical and administrative feasibility of implementing an alternative and the availability of various services and materials required to accomplish its implementation.

Detailed analysis of alternatives3
Detailed Analysis of Alternatives

Cost –

  • Developing conservative cost estimates based on the materials needed and the construction elements associated with implementing the alternative.

  • Cost do not necessarily represent the cost the may actually be incurred because many design details are preliminary at this stage.

Slides held in reserve
Slides Held in Reserve

  • Use these slides only if there a specific questions