Presentation on theme: "CON MINE CLOSURE & RECLAMATION PLAN OVERVIEW February 22 nd, 2007."— Presentation transcript:
CON MINE CLOSURE & RECLAMATION PLAN OVERVIEW February 22 nd, 2007
Current Status of the Closure & Reclamation Plan All sections of the plan (with the exception of the reclamation cost estimate) have been reviewed by the Con Mine A&R Working Group set up by the MVLWB in 2003 The Working Group has met ~ 20 times over the past 4 years to discuss technical details of the proposed reclamation plan for the Con Mine site The Working Group provided recommendations on each section of the Plan that led to Miramar revising each section prior to submission to the MVLWB
Status of the Con Mine Closure & Reclamation Plan Three public information sessions (open house style) were held in 2005/06 to present the content of each Section to the public and to elicit feedback In December of 2006 the MVLWB completed their review of all sections of the Reclamation Plan (except the reclamation cost estimate); The Board has given conditional approval to each section indicating what changes were needed to satisfy the MVLWB. Miramar has revised the Plan to incorporate these changes and formally re-submitted the Plan to the MVLWB at the end of January 2007 for final Board approval
Status of the Con Mine Closure & Reclamation Plan The MVLWB Board staff have indicated that this revised version of the Plan will be sent to the Working Group for one final review to confirm that the Board’s conditions have been met – this meeting. Once the Plan is approved, Miramar will implement the Plan starting in 2007, with most physical reclamation work completed by the end of Water treatment and post closure monitoring and maintenance will continue at least through Leased land held by Miramar can be returned to the GNWT starting in 2007.
Status of the Reclamation Cost Estimate Miramar submitted a revised reclamation cost estimate to the MVLWB in December of Revised cost estimate is $12.5 million, not including work completed through ~60% of this cost is direct physical reclamation while 40% is for ongoing water treatment and post closure monitoring and maintenance. MVLWB has asked INAC to review this cost estimate and provide the Board advice regarding any revision to reclamation security levels.
Status of the Reclamation Cost Estimate Miramar currently has $10.0 million in security set aside for reclamation of the Con Mine – –$9.0 million in an environmental trust set aside for reclamation from the sale of the Bluefish hydro facility pledged to INAC under the Water License – –$1.0 million in a second trust set aside for reclamation from the sale of the Bluefish hydro facility Miramar estimates that it will spend an additional $4 million on final reclamation in Consequently by the end of 2007, the amount held in two reclamation trusts will exceed the remaining estimated reclamation liability Final clean up and treatment of the remaining arsenic sludges through the autoclave is scheduled for completion by September of 2007 leading the way for mill demolition in late 2007 – early 2008.
Structure of the Con Mine Closure & Reclamation Plan Table of Contents 1. 1.Introduction and History 2. 2.Site Infrastructure and Facilities 3. 3.Underground Workings 4. 4.Rat Lake 5. 5.Con Pond and Negus Pond 6. 6.Tailing Containment Areas (TCA’s) 7. 7.Contaminated Soils 8. 8.Water Management 9. 9.Closure and Post Closure Site Monitoring Cost Summary and Schedule
Public Information Session #1 - Held - June 15 th, 2005 Sections Covered: 1. 1.Introduction and History 2. 2.Site Infrastructure and Facilities 3. 3.Underground Workings 4. 4.Rat Lake Public Information Session #2 -Held October 26 th, 2005 Sections Covered: 5. 5.Con Pond and Negus Pond 6. 6.Tailing Containment Areas (TCA’s) – Historic Areas – Recently Active Areas (Upper and Middle Pud) Public Information - Session #3 - Held March 16 th, 2006 Sections Covered: 7. 7.Contaminated Soils 8. 8.Water Management 9. 9.Closure and Post Closure Site Monitoring
The key reclamation objective is to return the minesite to a viable, and wherever practicable, self- sustaining ecosystem End land use objective is a mix of land suitable for industrial use mixed with open space Areas not impacted by mining could be used for other purposes pending appropriate setbacks There will be three sites designated as hazardous sites (Con and Negus Ponds and the hazardous materials storage site) that will be capped and thus not available for future land use
Specific Reclamation Objectives Progressive Reclamation activities started in 2002 Mill area to be reclaimed to a standard suitable for future industrial land use Similarly the Shops/Office/Roads/Parking areas to be reclaimed to industrial land use standard Historic Tailing Areas to be drained, contoured and revegetated – 35 hectares Upper and Middle Pud TCA’s to be covered with 50 to 60 cm of rock and vegetated – 50 hectares
Section 1 - Introduction History and Reclamation Objectives History and Reclamation Objectives No Comments received from MVLWB and the Working Group.No Comments received from MVLWB and the Working Group.
Section 2 - Infrastructure and Facilities All buildings on Site are to be removed, with potentially 3 exceptions: Masonic Lodge One private residence Recreation Hall Exceptions subject to approval of the land owner (GNWT) - copies of letters from these 3 interested parties have been submitted to Water Board. A procedure has been added that deals with the assessment of concrete foundations for contaminants. A procedure covering the removal of the timber and concrete crib at the boiler house at the Con dock has been added (Section 2.7). This procedure references DFO guidance to monitor the work to protect fish and commits to obtaining DFO approval of the detailed work plan prior to proceeding.
Mill complex at present. Mill Complex – July 2005
Section 3 - Underground Mining ceased September Monitoring of water level and quality in mine has been carried out twice since then. In 2006, a procedure was developed to monitor minewater (level and quality) on an annual basis. This procedure is set out in detail in Sections 8 and 9. Initially the minewater will be monitored at a minimum frequency of once each year, with the results reported to MVLWB and INAC. Information will be made public. In the summer of 2006 water was measured to at the 4700 foot level. At current flooding rates water is expected to equalize near surface in Capping of shafts and raises in progress.
Section 4 - Rat Lake The majority of the Rat Lake sediments were evaluated in A further ~2,000 cubic meters were removed in The ‘Rat Lake Work Plan’ that detailed what was done and what results were obtained to the end of 2005, has been submitted to the MVLWB (January 2007). The last 100 cubic meters of contaminated material was removed in September 2006 and the tests results from that work are pending (report to be submitted to the MVLWB in March 2007). The Reference to the YASRC is added. MCML has included in the Plan commitments #10,16 and 17. Section 4.1 and 4.2.
Section 5 - Con and Negus Ponds Arsenic sludges have been removed and stockpiled in the Blend Plant for treatment in the Autoclave. The Autoclave will be commissioned in April 2007 and remain in service until all of the arsenic sludges have been treated. Con Pond has been cleaned and power washed to recover the remaining arsenic sludges. Cleaning of the Negus Pond will be completed in As the gravel and boulders are removed, they will be washed and the wash water will go to the Autoclave as feed for the treatment of the arsenic sludges. Any gravel or boulders that have total arsenic over 340 mg/kg on the surface of the rock will be placed in the hazardous waste disposal site for permanent care and storage.
Section 5 - Con and Negus Ponds The cleaned areas will be graded to direct surface runoff to the Middle Pud TCA Low permeability engineered cover has been designed for these two ponds with the objective of reducing infiltration to < 2%. Cover will include a Geosynthetic Clay Liner (low permeability liner) which has a ‘clay’ core. As such, it is expected to have a long life (+100 years) as compared to synthetic liners (plastic / HDPE). The water quality of groundwater down gradient of the capped ponds will be assessed by monitoring wells.
Section 5 - Con and Negus Ponds The GCL liner will be capped with a coarse gravel / cobble material that is both physically and chemically stable. As set out in Section 5.3.1, the gravel will be tested to confirm that the upper layer will have arsenic levels less than 340 mg/kg of total arsenic. If needed, a quarry would be developed north of the water treatment plant to provide cover material. The quarry would be closed in a manner consistent with the Closure guidelines established by INAC for open pits or quarries (end of Section 5.3.1). A large boulder barrier will be constructed and maintained to prevent inadvertent access to these areas by motorized vehicles.
Con Pond – July 2005 Con Pond in center of photograph
Con Pond with rock cover at closure Con Pond at Closure in 2008
Negus Pond – July 2005
Negus Pond at Closure in 2008 Negus Pond with rock cover. Large rock barrier not shown for clarity.
Calcine storage area ‘cleaned out’ for waste storage Calcine Storage Area – July 2005
Rock cap on hazardous waste storage site. Mill complex is removed from area at bottom of photo. Hazardous Waste Storage Site – September 2008
Cover System for Hazardous Waste Disposal Site and Hazardous Waste Sites Hazardous Waste Site Cap Design
Section 6 - Tailing Containment Areas (TCA’s) Historic and Recently Active Historic – Negus, Neil Lake, Lower Pud Lake and Crank Lake TCA’s will be drained, contoured and revegetated. Recently Active – Upper Pud and Middle Pud TCA’s will be capped with a minimum 50 to 60 cm layer of broken rock and then seeded and fertilized. Soil will be imported to create “islands” on the surface of the TCA to enhance the rate and success of vegetation establishment on the rock.
Section 6 - Tailing Containment Areas (TCA’s) Historic and Recently Active A section has been added to the Closure Plan to detail how vegetation success will be measured and what criteria will be used to determine when additional contingent measures are needed. Section sets out a series of contingency plans that describe additional measures that will be taken by MCML if the vegetation cover is not successful within 4 to 5 years.
Section 6 - Tailing Containment Areas (TCA’s) Historic and Recently Active The details for the engineered cover to be placed on the Upper and Middle Pud TCA have been included in Section The details outline the initial modeling used to check the design and present the material specifications that will needed to achieve the target infiltration (< 7%) for the cover. A test pad was developed in 2005 and is being monitored for physical stability. It was seeded at that time and is being used to evaluate vegetation success on the rockfill. Further studies are planned in 2007 to confirm the modeling used in the design. With the exception of rock outcrops, the surface area will be vegetated. Fertilizer will be added and the area over-seeded for the first several years to enhance success.
Neil Lake – July 2005
Neil Lake as revegetated in 2008, Kam Lake in background. Note Water Treatment Plant still in place. Neil Lake – 2010 Projection
Upper Pud - July 2005
Upper Pud, capped with waste rock and gravel. Note vegetation starting to show. Upper Pud - July 2010 Projection
Vegetation cover now established on Upper Pud TCA Upper Pud – 2015 Projection
Cover Test Pad on Upper Pud June 2006
Test Pad for Vegetation on Mine Rock Cover
Section 7 Contaminated Soils: Minesite has been impacted by 65 years of mining Areas of impact have been identified Site has been divided into 4 zones to facilitate closure and reclamation. The Zones are: Zone 1 - Blend Plant/Negus Pond, Con Pond, Hazardous Waste Disposal Site Zone 2 – Tailing Areas: Upper Pud, Middle Pud, Lower Pud, Neil Lake, Negus Tailing, and Crank Lake Zone 3 – Main mine lease with mill area, Robertson headframe, and area around tailing areas to north, west and south Zone 4 – Rat Lake, Tin Can Hill, Con Camp and Dock, and Mosher Island.
Section 7 Contaminated Soils: Closure plan for Zone 1 is discussed in Section 5. Closure plan for Zone 2 is discussed in Section 6. Closure plan for Zones 3 and 4 are discussed here. The closure plan for Zone 3 is considered in 2 parts. Area 1. Mill and headframe buildings will be removed. Impacted soil will be placed in the hazardous waste disposal site or the non- hazardous waste site as determined by testing. Area will be reclaimed to the NWT industrial use standard. Area 2. Soil in the areas to the north, west and south of Zone 2 (active tailing basins) will be tested. Site specific plans to close these areas will be developed based on the results of testing.
Section 7 Contaminated Soils: The closure plan for Zone 4 (Rat Lake, Tin Can Hill and Con Dock) started with testing of soil at 8 sites identified as having arsenic contaminated soil. In addition to arsenic, all metals on the GNWT contaminated sites list were included in the testing program. If any metal on the list is exceeded and determined not to be naturally occurring, then the sites will be evaluated to determine if clean up is necessary. Data to date suggests, once the arsenic contaminated soils are removed or cleaned up, the other metals of concern are removed. The test results indicated that arsenic at 5 of the sites is naturally occurring mineralization – not a result of mining. The others sites will be further investigated. The rest of Zone 4 was inspected and no other contaminated sites were identified. If additional sites are found in the next 4 years, a site specific closure plan will be developed for each area.
Section 7 Contaminated Soils: In 2007, sites away from the main mine area – mill and Robertson Headframe - will be tested to confirm the extent and type of arsenic that may be present in the soil. Water that collects in the excavations at the mill will be directed to construction sumps in the excavation area. These sumps will be pumped and the water directed to the Middle Pud TCA. Section 7.4 details the plan to clean up the mill site and clean the depressions in the rock surface once the mill is removed.
Section 8 Water Management: Since the early 1980’s surface water on site has been collected and directed to the Middle Pud TCA and then to the Water Treatment Plant. Water treated at the plant, and at nine sampling stations around the site, has been monitored under the Water License since the early 1980’s. Regulatory limits for these contaminants are set out in the Water License and in federal MMER regulations. These will continue to be applied following Closure and will apply to minewater once it nears the surface. If the limits are exceeded, the minewater would be pumped to the Middle Pud TCA for treatment.
Map of Current SNP Sites
Section 8 Water Management: Engineered structures control site surface drainage. The Closure Plan provides further improvement to the system. Offsite flows not directed to Middle Pud are minimal and have not been in contact with impacted areas. These flows are currently monitored by the Surveillance Network Program (SNP) under the NWT Water License. Rat Lake clean up is complete and a final report will be submitted in March The report includes the results of the speciation tests.
Section 8 Water Management: The Closure Plan creates additional surface water monitoring stations and will monitor the quality of the minewater as it approaches the surface. Six groundwater monitoring wells have been installed and several more are included in the Closure Plan, including 2 deep wells adjacent to mine workings. Monitoring at these additional stations will continue and be required under future Water Licenses.
Section 8 Water Management : Minewater and mine flooding. URS sampled underground minewater in 2004 MCML sampled underground minewater in Mine flooded to 4700 Level as of September Minewater is expected to reach surface in late 2014, thus Con Mine will take ~11 years to flood. Water quality testing indicates minewater is relatively clean – Zinc is only parameter above Water License limit. Closure Plan calls for installation of access points in the concrete caps at Robertson Shaft, C-1 Shaft, and 204Q Stope to allow for installation of pumps should it be necessary to pump and treat the minewater when it reaches surface.
Section 9 Closure and Post-Closure Monitoring Monitoring of the site is detailed in Section 9.1 and includes geotechnical inspections of the tailing dams, closed hazardous sites, and water management facilities. The cost estimate (Section 10) anticipates that environmental monitoring would continue for ~ 50 years, but the frequency of inspections would be reduced over time. Post-Closure monitoring is anticipated to continue unchanged for at least 25 years, or until water quality satisfies the Water License discharge limits and water treatment can be discontinued. The MMER and EEM programs would also continue to apply during that period.
Section 9 Closure and Post-Closure Monitoring The annual geotechnical inspection of the minesite includes the chemical and physical stability of the TCA’s, plus all dams, dykes and drainage channels. The inspection will be expanded to include caps on the openings to surface, and the results of groundwater monitoring. A report of each inspection, and a plan outlining any required action, would be sent to the MVLWB, the INAC Inspector, and Environment Canada.
Section 9 Closure and Post-Closure Monitoring Federal Environmental Effects Monitoring (EEM) has been in effect since June Numerous parameters, including 36 metals, are routinely monitored. Post-Closure monitoring includes EEM and this will continue at least for the next 6 to 9 years. Other than arsenic, EEM has not detected any other metals at levels of concern. In addition to contaminants, EEM monitors the environmental effects of treated effluent on the receiving water, including fish and other biota.
Section 10: Cost Summary & Schedule Submitted to MVLWB in December 2006 Remaining closure costs estimated at ~$12.5 million
2007 Planned Reclamation Complete treatment of all remaining arsenic sludges. Decommission and start to remove Blend Plant structure. Begin dismantling and removal of remaining surface structures, including mill complex and headframes. Perform cycle 3 of minewater sampling Install remaining groundwater wells.
2008 Planned Reclamation Complete demolition and removal of remaining surface structures. Begin reclamation of Upper Pud TCA. Cap 204Q stope opening. Cap Robertson / C-1 Shaft openings. Perform cycle 4 of minewater sampling. Begin reclamation of Middle Pud TCA. Continue closure monitoring.
2009 Planned Reclamation Complete reclamation of Upper Pud TCA. Continue reclamation of Middle Pud TCA. Perform cycle 5 of minewater sampling. Complete any remaining tasks. Commence Post-Closure monitoring.
2010 Planned Reclamation Complete reclamation of Middle Pud TCA. Over seed and fertilize revegetated areas. Perform cycle 6 of minewater sampling. Complete any remaining tasks. Continue Post-Closure monitoring.
Status of Con Mine Water License Current license expires on January 30 th 2008 Miramar will ask that the Water License be renewed to cover the period from January 2008 thru December 2014 – i.e. thru the 4 year physical reclamation period and into the start of the post closure monitoring period. The renewed license will allow for reclamation, ongoing water treatment and post closure monitoring and maintenance (no further mining or milling). This license period will allow the reclaimed site conditions to become stable. Subsequent Water Licenses will address the long term monitoring and maintenance requirements. Miramar will submit the application in 2007 once the Closure Plan has been approved.