Silver Dyke Adit 1551984 - R8 SDMS · 2021. 1. 10. · adit. Silver Dyke Mine Conceptual Model....
Transcript of Silver Dyke Adit 1551984 - R8 SDMS · 2021. 1. 10. · adit. Silver Dyke Mine Conceptual Model....
Lower Rebellion
Silver Dyke Adit
Currently Three Operable Units
Sih-Mem Creek
Carpenter Creek Snow Creek
Neihart Slope
Belt Creek
Boundaries are subject to change
Town of Neihart OU1 (red), Mine and Watershed OU2 (yellow), and Silver Dyke Complex OU3 (green)
Meeting Objectives
• Status of the OU01 Town of Neihart Cleanup • Brief overview of Silver Dyke Mining Complex and
work completed to date including the findings of remedial investigation as it pertains to Operable Unit 3 (Silver Dyke Mining Complex)
• What’s next for Carpenter Snow Creek?
Meeting Objectives
• Status of the OU01 Town of Neihart Cleanup • Brief overview of Silver Dyke Mining Complex and
work completed to date including the findings of remedial investigation as it pertains to Operable Unit 3 (Silver Dyke Mining Complex)
• What’s next for Carpenter Snow Creek?
Overview Silver Dyke Mining Complex
• Operated from 1923 – 1929• Block mined from below resulting in
glory hole• Averaged 170,000 tons ore/year• Problems with milling early on due
to oxide and sulfide minerals• Waste disposal problematic• Perennial discharge coming from
adit
Silver Dyke Mine Conceptual Model
Aquafix Study 1. Seasonal fluctuations in flow and water chemistry will make maintaining a constant pH very difficult. Can a semi-passive system be operated effectively year-round in a remote location with minimal operation and maintenance?
2. What are the annual costs?
3. How much sludge will be generated? Will sludge pass TCLP?
4. How much TSS and TDS is generated compared to baseline?
5. Are there improvements in water quality (SW & GW) downstream?
EPA’s removal program initiated a removal action at the Silver Dyke Tailings in 2014
Approximately 34,000 cubic yards of mine tailings removed and placed in MacKay Gulch Repository
Silver Dyke Tailings Impoundment
Post Removal 2016Some erosion controls and revegetation measures necessary
Mackay Gulch Repository- Slope grade less than 4:1- Contains 180,000 cys of cover and top soil
- Infrastructure improvement- 675,000 cubic yard capacity
- Waste - Adequate separation to gw- Easy Access- One property owner- Minimal preparation- 34,000 cys placed there in
2014
Silver Dyke Glory Hole Repository
- Infrastructure improvement- Headwall removal- 570,000 cubic yard capacity- Positive drainage- No cover or top soil- Adit discharge
- Public support- Adequate separation to gw- Fairly Accessible- One property owner- May reduce adit discharge
Silver Dyke Glory Hole Hydrogeologic Work
Remedial Investigation Report
• The RI Report currently undergoing Agency review is a comprehensive report for OU2 and OU3• Evaluates data collected through 2012
• Addresses mine waste piles; streamside/floodplain deposits; groundwater; seeps, adits & shafts; surface water; sediments; road beds; residential properties; and terrestrial/aquatic populations that may be impacted by Site waste
700,000 cys OU3
350,000 cysNeihart Slope
110,000 cys Snow Creek
Unknown volume Belt Creek & lower Carpenter Creek
150,000 cys OU01
Mine waste volume estimates by study area
OU3 Mine and Mine Related Locations
Carpenter Creek Tailings 9 Seasonal Residential Properties located along Carpenter Creek and another below glory hole
Lead ranges from 197 mg/kg to 6,280 mg/kg
Over 500,000 cys
An unknown quantity of tailings are in Carpenter Creek from the confluence with Snow Creek to Town of Monarch (approx 14 stream miles)
OU3 Groundwater Investigations
OU3 Adit Discharge Locations
Meeting Objectives
• Status of the OU01 Town of Neihart Cleanup • Brief overview of Silver Dyke Mining Complex and
work completed to date including the findings of remedial investigation as it pertains to Operable Unit 3 (Silver Dyke Mining Complex)
• What’s next for the Carpenter Snow Creek Site?
Fish BarrierDry Fork Belt Creek Fish Barrier
Westslope Cutthroat Trout Barrier
Fish Wildlife and Parks has secured funding to construct a fish barrier in Carpenter Creek
Mine Adit Treatability Testing
EPA’s Office of Research and Development has completed a laboratory bench scale test of Haystack Creek Mine and Big 7 Mine adit discharges
Results look promising for a sulfate reducing bioreactor – low flow (1 gpm); plenty of space; and adit discharge is acidic
Field implementation possible in 2017
Dewatered Compromise Shaft in October
Schedule
• 2017 - 2019: Remedial Action at OU01 Town of Neihart pending available funding –Infrastructure improvement on Carpenter Creek Road and placement of waste in the Mackay Gulch Repository. Multi-year remedial action
• 2017: The Remedial Investigation Report for OUs 02 and 03 - Expected to be finalized in mid 2017.
• 2017: Feasibility Study Report for OU3—Silver Dyke Mining Complex is expected to be finalized in mid 2017.
• 2017: Proposed Plan and ROD - A proposed plan for cleanup, a public comment period, and a ROD by end of year.
• 2018/2019: The Feasibility Study Report for OU2—Mines and watershed is expected to be finalized in late 2018/early 2019. This OU contains the mines on Neihart Slope, Snow Creek as well as streamside deposits in Carpenter Creek below OU3 to Monarch (approx. 15 creek miles).
• 2019: Remedial Design for OU03 – Following negotiations with Potentially Responsible Parties, the Remedial Design is expected to begin in 2019
• 2019: Proposed plan to clean up OU2 is scheduled to be completed in late 2019. This will be followed by a public comment period, and a ROD
Questions or Comments