British Columbia Mine Reclamation Symposium

Challenges and solutions to meeting Indigenous and stakeholder mine closure objectives in a remote, high… Bianchin, Mario; Miller, Elizabeth Fillatre; Gladu, Jeremiah; Wall, Dean 2019

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Notice for Google Chrome users:
If you are having trouble viewing or searching the PDF with Google Chrome, please download it here instead.

Item Metadata

Download

Media
59367-Bianchin_M_et_al_Mine_closure_objectives.pdf [ 2.43MB ]
Metadata
JSON: 59367-1.0391928.json
JSON-LD: 59367-1.0391928-ld.json
RDF/XML (Pretty): 59367-1.0391928-rdf.xml
RDF/JSON: 59367-1.0391928-rdf.json
Turtle: 59367-1.0391928-turtle.txt
N-Triples: 59367-1.0391928-rdf-ntriples.txt
Original Record: 59367-1.0391928-source.json
Full Text
59367-1.0391928-fulltext.txt
Citation
59367-1.0391928.ris

Full Text

    CHALLENGES AND SOLUTIONS TO MEETING INDIGENOUS AND STAKEHOLDER MINE CLOSURE OBJECTIVES IN A REMOTE, HIGH ALPINE ENVIRONMENT   Mario Bianchin, Ph.D., P.Geo.1 Elizabeth Fillatre Miller, M.Sc., R.P.Bio.2 Jeremiah Gladu, P.Ag., CSAP1 Dean Wall, M.Sc., P.Eng. 3   1Wood Environment & Infrastructure Solutions, 600-4445 Lougheed Highway,  Burnaby, BC V5C 0E4 2SNIPGOLD CORP A Subsidiary of Seabridge Gold Inc., 1235 Main Street,  P.O. Box 2536 Smithers, BC, V0J 2N0 3Wood Environment & Infrastructure Solutions, 203-601 Front Street,  Nelson, BC V1L 4B6  ABSTRACT The effective decommissioning and remediation of subsurface contamination (soil and groundwater) at former remote mine sites in British Columbia’s Northwest is challenging mainly due to seasonal and locational site access limitations. A Site Reclamation Execution Plan was developed to identify the best approach to decommissioning and remediation of the site that included innovative site-specific low-energy remedial methods coupled with site-specific risk-based remedial targets and on-site treatment/disposal. The site reclamation execution plan is supported by site investigations conducted from 2017 to 2019 to characterize potential contamination. The Johnny Mountain Mine was an underground gold mine located in traditional Tahltan Territory.  Core components included underground workings, tailings storage facility, fuel storage and ancillary fuel distribution facilities, the air strip and the mill building.  The approved reclamation plan included designing and constructing the upgrade of the existing landfill to hold non-hazardous demolition waste from the former structures, including historic burial sites, cleaned fuel tanks and the mill building.  Shallow fuel-impacted soil in and around the fuel storage and distribution facilities is being actively remediated on site while any deeper soil and groundwater contamination will follow a site-specific risk based remedial approach.  Reclamation of the site is possible with the collaborative support of the Tahltan Nation.     KEY WORDS landfill, hydrocarbon, soil and groundwater remediation        INTRODUCTION The effective decommissioning and remediation of subsurface contamination (soil and groundwater) at former remote mine sites in British Columbia’s Northwest can be challenging due to seasonal and locational site access limitations. Work is often restricted to a short summer field season due to the elevation and climatic conditions.  The physical remoteness of sites presents a logistical challenge for moving people, equipment and materials to and from the site, often limiting equipment resources to that which was left on site or is heli-portable.  In such situations, the best approach to site decommissioning and remediation often includes both innovative site-specific low-energy remedial methods coupled with site-specific risk-based remedial targets.  Prior to fully embarking on reclaiming the Johnny Mountain Mine (JMM) site, a detailed plan was needed that identified project risks, provided mitigative options to address the risks, met stakeholder requirements, and was able to be completed within an acceptable timeline and cost. To this end, a Project Execution Plan (PEP) was developed in 2016 to 2017 (Amec Foster Wheeler 2017).     The PEP was developed around the Approved Reclamation Plan associated with the Mine’s Permit (MEMPR 1988).   The execution plan is scheduled over a multi-year period starting in 2017, with planned visual progress expected to occur in each year. The process followed to develop the Reclamation Execution Plan is summarized in Error! Reference source not found.. The first step of the execution plan was to review the pre-existing information including the reclamation plan and permits, previous investigations and reclamation work, and determine the gaps in data required to update the plan (where necessary) and to prepare a final defensive reclamation cost estimate (±10%) to the end of year 1 of site activities. Following the data gap analyses, field and analytical programs were established to obtain the required details, prepare feasible plans for each reclamation component, develop cost estimates, prepare a schedule and develop a project/construction management framework to effectively execute the required investigations. Design and construction activities in light of site logistic constraints were also included, all with the intention of implementing the necessary reclamation measures. Approved Reclamation Plan•Specifies objectives/requirements for site reclamationProject Execution Plan •Reclamation Execution Plan•Schedule and implementation strategyInitial Reclamation Execution Plan•Develop reclamation strategy based on pre-existing conditions (pre-2017)•Applies to Year 1 onlyAssess Data Gaps•Conduct site investigations in 2017 to address data gapsUpdate Reclamation Execution Plan•Update reclamation strategy and extend to 5-year planCommence Reclamation•Implement reclamation/remediation activities•Track progress and revise schedule accordinglyFigure 1: Figure 1: Site Reclamation Strategy Development 42nd Annual BC Mine Reclamation Symposium  Challenges and Solutions to Meeting Indigenous and Stakeholder Mine Closure Objectives in a Remote, High Alpine Environment     The purpose of this paper is to present the results and challenges of executing the Reclamation Execution Plan with a specific focus on identification of main waste issues through site investigation and the development and implementation of management solutions. Background History of Mining and Reclamation Activities The Site is located approximately 100 km northwest of Stewart, British Columbia and 85 km due west of Highway 37 (6277401N, 373149E). It is surrounded by other mining operations such as the former Eskay Creek Mine and advanced exploration projects including Kerr-Sulphurets-Mitchell (KSM) and Galore Creek (see Error! Reference source not found.). The Site is situated within the Coast Mountain Range east of Alaska’s pan handle and the Craig River and 6 km south of the Iskut River with an elevation of about 1,100 m above mean sea level (masl). The Site dimensions are approximately 700 m by 1,000 m and legally described as District Lots 7031 and 7032 of the Cassiar Land District.  Site activities are currently staged from the Bronson Airstrip Exploration Camp (Bronson Camp) located adjacent to the Bronson River. The camp is accessed by helicopter from the McLymont Laydown, which is reached by Eskay Creek/Atlas Gas Access Road located approximately 40 km north of Bell II located on Highway 37. Access to the Johnny Mountain Mine Site location from Bronson Camp is by the 10 km long Johnny Mountain access road. When JMM was operational, supplies were delivered by air using the airstrip on Site or by boat from the coast up the Iskut River to the Snip mine and then up the Johnny Mountain access road.  The Johnny Mountain Mine was an underground mine that saw development from 1986 to 1988 with mining/milling beginning in 1988. Mine production included producing gold, silver, and copper concentrate. Mining operations were relatively short-lived and occurred from November 1988 to August 1990, and from September to November 1993 when operations were stopped. Mining facilities included three adits (numbered 10, 11, and 12), five vent shafts, a mill building, a tailings facility, an air strip (at the Mine Site), a fuel tank farm, several ancillary buildings, waste rock piles, a 10-km road from the Bronson Slope area situated adjacent to the Iskut River to the mine, a septic bed, and a few other minor components. The milling process comprised conventional grinding and gravity separation, which initially included a cyanide leach process. Due to inefficiencies, the cyanide leach process ceased during active mining operations.    At its peak of operation, the total area of ground disturbance was reported at 67.55 ha with 48% associated with mine access and exploration roads (Woznow and Yeager, 1999). The tailings impoundment constitutes 17% of the total disturbed area (11.5 ha). A detailed account of surface and underground disturbances is provided in Woznow and Yeager (1999). Details of existing and former JMM facilities, as required for areas of potential environmental concern (APEC) identification, are discussed in Sections 2.7 Current Built Environment and 2.8 Former Built Environment. Detailed description of mining facilities is provided in Woznow and Yeager (1999) and Greenwood Environmental (2015). Reclamation activities at the former Figure 2: Site Location 42nd Annual BC Mine Reclamation Symposium  Challenges and Solutions to Meeting Indigenous and Stakeholder Mine Closure Objectives in a Remote, High Alpine Environment     Mine Site are being completed according to the Reclamation Plan dated October 13, 1999 (Woznow and Yeager, 1999) and submitted to the Ministry of Energy and Mines (October 15, 1999). Table 1 provides a summary of Site Facilities that existed in 1999 and in 2016, following reclamation activities during that period.  The location of the historic mining facilities are shown in Error! Reference source not found..  There are currently three BC Government permits applicable to the JMM as follows: • Reclamation Permit M-178, dated June 17, 1988, and amended July 7, 2004; • Water Management Permit PE-8415 dated June 6, 1990, amended May 11, 2000, and later on June 10, 2019; and • Water Management Permit PR-7927 dated March 29, 1989 and amended July 14, 1999, August 2, 2011 and later on May 31, 2018. Site conditions and ownership have changed since the original reclamation plan was prepared and for which these permits were provided and ultimately approved (Fillatre Miller et al. 2019). The Reclamation Execution Plan included the required investigative, design and decommissioning work to meet the requirements of the approved reclamation plan and to appropriately adjust the specific reclamation works.  Table 1: Status of Site Facilities in 1999 and 2016 10-Level 1999 2016 Concentrator and ancillary structures Existing Existing Tailings pond and ancillary structures Existing Existing Storage, core shack and warehouse buildings Existing Removed Accommodation, kitchen and office buildings Existing Removed Portal and support structures Existing Existing Fuel storage and ancillary facilities Existing Existing Reclamation research container shed Existing Removed Roads and airstrip Existing Existing Powder magazine Existing Removed Scrap metal yard Existing Removed Core storage area Existing Existing 11-Level   Storage buildings Existing Removed Mechanics shop Existing Removed Portal and support structure Existing Existing Equipment storage site Existing Existing Mid-level diamond arch warehouse Existing Removed Reclamation research container shed Existing Removed Roads Existing Existing 12-Level   Portal Existing Existing Ventilation fan housing structures Existing Existing Roads Existing Existing Zephrin and pickaxe surface trenches Existing Removed Prospectors cabin (uphill from 12-Level Portal) Not Reported Existing      Figure 3: Johnny Mountain Mine Historic Mining Operations and APECs      General Site Physiography The Johnny Mountain Mine Site is very mountainous with relief at the Site ranging from about 2,200 metres above sea level (masl) at Johnny Mountain to approximately 1,000 masl at the Mine Site dropping to 120 masl in the Iskut Valley. The Mine Site is situated on the northern flank of Johnny Mountain with the Craig River Valley and its tributary, and the Iskut River Valley situated on the western flank.  The Site is situated in an alpine tundra setting with adverse climate that is too cold and windy to support tree growth. The area is generally covered in low-lying vegetation consisting primarily of mosses. The Site is located on a plateau characterized by three different watershed management areas: Johnny Creek, Sky Creek, and Stonehouse Creek (Woznow and Yeager, 1999). The southern portion of the Site is bounded by uplands that are covered in glaciers. Johnny Creek flows north and discharges to Bronson Creek which flows west and discharges to the Iskut River. Stonehouse Creek drains to the southwest and discharges to the Craig River. Sky Creek originates from the area to the west of the airstrip, which includes the tailings impoundment. Sky Creek drains to the northwest and discharges to the Iskut River. These streams comprise freshwater habitat, although fish are only found at lower elevations in the Craig River, Bronson Creek, and throughout the Iskut River (RTEC, 2017a). Discharges for all three creeks exhibit a bi-modal distribution associated with spring or summer snow/glacial-melt followed by fall rainfall storm events.  Climate The Site is, based on elevation, at the transition zone between the coastal and interior climatic zones. The Site is characterized by average annual temperature of about 0.1ºC with a large range from -24.74ºC in January to 26.06ºC in August. Typical precipitation levels for the Coast Mountain Range is between 2,000 mm and 2,600 mm ranking among the highest for British Columbia. The majority of precipitation occurs from September to May and approximately 55% of the precipitation occurs as snow from November to May.  SITE INVESTIGATION The Reclamation Execution Plan called for the completion of a site investigation to identify potential areas of subsurface contamination related to historic mining activities.  The site investigation was initiated with the completion of a desktop study which identified Areas of Potential Environmental Concern (APECs). Based on the findings of the desktop study, 14 APECs were identified and are displayed on Error! Reference source not found.. The APECs and their associated potential contaminants of concern (PCOCs) are summarized in Table 2. Table 2: Areas of Potential Environmental Concern (APECs) APEC Potential Contaminants of Concern  Potentially Affected Media # Description Soil Ground Water 1 Mill /10 Level Portal  Anions & Nutrients   PCBs   PHCs/PAHs/VOCs   Metals     Cyanide   2 Tank Farm Area Anions & Nutrients   42nd Annual BC Mine Reclamation Symposium  Challenges and Solutions to Meeting Indigenous and Stakeholder Mine Closure Objectives in a Remote, High Alpine Environment     APEC Potential Contaminants of Concern  Potentially Affected Media # Description Soil Ground Water PHCs/PAHs/VOCs   Metals   3 Main Warehouses PCBs   PHCs/PAHs/VOCs   Metals   Cyanide   4 Fuel Pump Shed Anions & Nutrients   PHCs/PAHs/VOCs   Metals   5 Mechanical Shop / 11 Level Portal   PHCs//PAHs/VOCs   Metals    6 Septic Field  Anions & Nutrients   PHCs/PAHs/VOCs   Metals   7 Tailings Impoundment  Anions & Nutrients   PHCs/PAHs/VOCs   Metals   Cyanide   8   12 Level Portal PCBs   PHCs/PAHs/VOCs   Metals   Cyanide   9 Main Landfill Anions & Nutrients   PHCs/PAHs/VOCs   Metals   Cyanide   10 Burial Site 1 (Fmr. Chalet) Anions & Nutrients   PCBs   PHCs /PAHs/VOCs   Metals   Cyanide   11 Airstrip Anions & Nutrients   PHCs/PAHs/VOCs   Metals    12 Burial Site 2 Anions & Nutrients   PHCs/PAHs/VOCs   Metals   Cyanide   13 Warehouse East Area PHCs/PAHs/VOCs   Metals    14 Fuel Lines Anions & Nutrients   PHCs/PAHs/VOCs   Metals    Cyanide   42nd Annual BC Mine Reclamation Symposium  Challenges and Solutions to Meeting Indigenous and Stakeholder Mine Closure Objectives in a Remote, High Alpine Environment     Notes: APEC = Areas of Potential Environmental Concern PHCs = EPH, LEPH, HEPH and VPHs (defined below)  EPH = light/heavy (C10-19/C19-32) extractable petroleum hydrocarbons without correcting for PAH HEPH = heavy (C19-32) extractable petroleum hydrocarbons corrected for PAH LEPH = light (C10-19) extractable petroleum hydrocarbons corrected for PAH  VPH = volatile (C6-10) petroleum hydrocarbons  PAHs = polycyclic aromatic hydrocarbons  VOCs = volatile organic compounds includes BTEX  BTEX = benzene, toluene, ethylbenzene, and xylenes   In 2017 a site investigation was conducted at the JMM site.  The objectives of the site investigation were to: 1. Confirm the absence/presence of contamination at APECs 2. Delineate contamination where observed; and 3. Collect sufficient information of subsurface conditions (contamination, soils and groundwater) to support either numerical-standards or risk-based strategy for site remediation. The 2017 environmental site investigation included a drilling and test pitting program.  In total,  52 boreholes were advanced on the JMM Site (see Error! Reference source not found.) to address potential contamination associated with the identified APECs (see Table 2: Areas of Potential Environmental Concern (APECs). With the exception of a few locations, most locations saw the advancement of shallow (<3 m) and deep (5 m to 20 m) boreholes for the installation of nested monitoring wells. All boreholes advanced on the Site were completed as monitoring wells. The drilling event included the monitoring of all Site groundwater monitoring wells.  All boreholes were advanced using an heli-portable air-rotary drill rig.   A total of 53 test pits were excavated on site to map hydrocarbon- and metal- contaminated soils in the APECs and PAG-material in the airstrip.  The test pitting program included 20 test pits as part of the borrow source investigation. Single-well hydraulic testing was conducted on all monitoring wells to generate a substantive database on hydraulic conductivity estimates of hydrostratigraphic units across the Site.  An extensive groundwater monitoring program was established that included bi-annual manual measurements of water levels and groundwater sampling.    Overall, the groundwater investigation provided sufficient information to map potential source to receptor groundwater flow path and travel times, which is necessary for the risk-based remedial approach.     Figure 4: Johnny Mountain Mine 2017 Site Investigation     INVESTIGATION RESULTS Site investigation results indicate that contamination was present in APECs related to former operations.  These APECs were carried forward as Areas of Environmental Concern (AECs) and targeted for additional investigation and remediation to address the identified contamination. A summary of AECs carried forward for further additional investigation and targeted for remediation are provided in Table 3. Areas of Environmental Concern are also shown on Error! Reference source not found.. Table 3: AECs and COCs AEC # and Description Contaminant Source(s) PCOCs / COCs Proposed Assessment Action AEC 1 Mill Building Diesel fuel, lubricants, ore, and process waste Soil: HEPH, arsenic, barium, copper, cobalt, and selenium Confirm lateral extent bound at a maximum by the area of the former Mill Building works Groundwater: LEPHw, EPHw10-19, cadmium, antimony, cobalt, iron, and manganese AEC 2 Tank Farm and Fuel Lines Diesel fuel, Avgas and possibly gasoline Soil:  VPH, LEPH Confirm vertical and lateral extent of contamination Groundwater: naphthalene and manganese AEC 3 Fuel Pump Shed Diesel fuel and Avgas Soil: LEPH Delineate vertical and lateral extent of contamination Groundwater: none AEC 4 Mechanical Shop / 11 Portal Fuels, lubricants, and waste rock storage Soil: toluene, xylenes, VPH, LEPH, HEPH, and copper Confirm vertical and lateral extent bound at a maximum by the area of the former Mechanical Shop fill pad.  Groundwater: none AEC 5 Main Landfill Unconfirmed. Inferred diesel fuel Soil: none Delineate vertical and lateral extent and confirm presence/absence of contamination.  Inferred localized issue. Groundwater: benzene, ethylbenzene, toluene, xylenes, LEPHw, and naphthalene AEC 6 JMM Airstrip Waste rock. Soil: to be investigated Conduct groundwater quality baseline assessment. Groundwater: antimony, arsenic and cobalt      Figure 5: Johnny Mountain Mine 2017 Site Investigation and AECs      The 2017 site investigation results, coupled with pre-existing information of historic mining and reclamation activities, lead to the identification of four main sources of waste that requires management.  These main sources of waste include: 1. Demolition/non-hazardous Waste: Mill Building, ancillary supporting structures associated with underground facilities, identified buried waste (from previous reclamation activities). 2. Hazardous Waste: Identified hazardous chemical constituents primarily associated with the contents of the Mill Building. 3. Potentially Acid Generating (PAG) materials: PAG material was identified in waste rock from underground mining operations which was used to construct the portal pads, grading around the Mill Building and repairing the airstrip.  Investigations conducted by Price et al. (2004) and supplemented by additional investigation data from the 2017 site investigation mapped areas of the mine site containing PAG material.  Additional PAG delineation was conducted in 2018 and scheduled for 2019 to provide better resolution in delineating affected areas and minimizing costs of disposal.  4. Hydrocarbon Contaminated Soils: Primarily associated with the former Tank Farm and with smaller isolated areas associated with the Mill Building and former Machine Shop. 5. Hydrocarbon Contaminated Groundwater: Primarily associated with the former Tank Farm. Smaller isolated contamination exists near the Mill Building and Landfill. 6. Metal Impacted Groundwater: Elevated concentrations of metals were observed in groundwater beneath the Mill Building and in the general vicinity of the airstrip. The approach to remediation or management of these wastes a JMM are discussed in the following section.       WASTE MANAGEMENT STRATEGIES  The management of wastes at the JMM Site is completed in accordance with the Closure Plan, as well as, applicable provincial regulations.  As discussed previously in the Reclamation Execution Plan, the management of wastes needed to be conducted in a cost effective manner addressing the site logistical challenges including: site isolation and being Heli-accessible only; physiographic and climatic conditions such the cold alpine environment resulting in a relatively short field season in which to conduct reclamation activities, engineering challenges related to high winds and precipitation, as well as, the limited availability of heavy machinery.  All of these logistical factors were included in the development of the Reclamation Execution Plan and factored into the site reclamation budget.     A key approach to reclaiming the site was the segregation of wastes in accordance to hazard level which would reduce the volumes of each class of waste to be managed and applying an acceptable remediation method to mitigating the risk to the environment.  As such, the Reclamation Execution Plan identified waste management plans that included on-site treatment, off-site disposal, landfilling and risk-based management. The Reclamation Execution Plan and associated waste management strategies/approaches needed to be acceptable to the Tahltan Heritage Resources Environmental Assessment Team (THREAT) who report to the Tahltan Central Government (TCG) Lands Department and are mandated with protecting Tahltan 42nd Annual BC Mine Reclamation Symposium  Challenges and Solutions to Meeting Indigenous and Stakeholder Mine Closure Objectives in a Remote, High Alpine Environment     environmental, social, cultural, heritage and economic interests.  Critical to the success of the Reclamation Plan was the support of the TCG.  SnipGold solicited the support from TCG through the following actions: • The Project Execution Plan was sent to TCG and THREAT for input. • Tahltan Nation Development Corporation were hired for equipment operators and laborers when qualified and available.  • Site Tours were offered to TCG and THREAT employees. • An annual presentation on previous years tasks completed as well as upcoming planned activities was given to TCG, the Tahltan Band and the Iskut Band. • TCG was updated on a quarterly basis of progress at JMM reclamation.  Chad Day, President of Tahltan Central Government, demonstrated his support for the project as follows:  “SnipGold has demonstrated clear and transparent intentions of addressing historic mining activities at the former Johnny Mountain Mine site, located in Tahltan Territory. We are pleased to work with them collaboratively to support and further the reclamation programs at the site by providing services through Tahltan businesses and people. We are pleased that SnipGold is addressing this historic issue and look forward to this continued relationship with SnipGold."  The following sections discuss how each identified waste stream was managed and the rationale for each approach. The waste management strategy for each general source of waste is discussed below.   Hazardous waste Hazardous waste primarily associated with chemical reagents and residues with the former milling process were inventoried and properly packaged for off-site disposal.  Hazardous waste constituted the smallest volume fraction of waste to be managed, and therefore in accordance with applicable regulations all hazardous waste was shipped off-site by helicopter.  Included in this inventory was the residual ore pile located in the conveyor/ore storage area of the Mill Building which likely served as the source of metal and sulfate contamination of groundwater.  Hydrocarbon Contaminated Soils Hydrocarbon contaminated soil was identified in the former tank farm and fuel line area.  Hydrocarbon contamination in soil was grossly delineated by the excavation of test pits and soil chemical quality was confirmed by laboratory analysis.  The large quantities of hydrocarbon-contaminated soil and the ease in which it can be bioremediated lead to on-site remediation of this waste.  Hydrocarbon contaminated soil residing above the groundwater table (generally less than 3 meters below ground surface) will be remediated on site in the location of the tank farm using the site excavators by bulking of hydrocarbon impacted soil into in-situ bioremediation piles.  The in-situ piles will be amended by a commercially available soil amender “Oil Gator” which prevents the leaching of hydrocarbons from the soil into groundwater and suppresses hydrocarbon vapours.  Oil Gator contains nitrogen, however, further addition of nitrogen and phosphorus in a granular form will be required based on nutrient testing.   The in-situ bioremediation piles will be mechanically turned with the excavator approximately every three weeks during the summer to aerate the soil.  Soil samples will be collected from the in-situ bioremediation piles throughout the year to assess the effectiveness of the bioremediation program. Demolition/non-hazardous Waste 42nd Annual BC Mine Reclamation Symposium  Challenges and Solutions to Meeting Indigenous and Stakeholder Mine Closure Objectives in a Remote, High Alpine Environment     Building demolition waste deemed non-hazardous constitutes a large volume of waste however, if managed appropriately constitutes a low risk to the environment.  As such all non-hazardous demolition waste will be managed through landfilling in the site’s existing permitted landfill (see Error! Reference source not found.). Demolition wastes include: buried material at two non-permitted burial sites; fuel tanks from the former tank farm, the Mill Building and any non-salvageable machinery remaining on site.   The Main Landfill has existed since 1994 at the current location on the west side of the Tailings Storage Facility (TSF).  Based on historic correspondence and discussions with the Ministry of Environment and Climate Change Strategy (MOE), several design upgrades were required to bring the landfill into compliance with Permit PR-7927, namely, separation of waste from groundwater, provision of a development boundary for the facility, and control of surface run-on and run-off.  These upgrades were described in detail in the Main Landfill Technical Assessment Report (TAR) dated 31 January 2018 and completed by Amec Foster Wheeler (2018).   The TAR included guidance on the following key design elements: • Placement of a levelling course of clean fill material on the base of the Main Landfill to ensure a minimum 1.22 m separation between waste and groundwater; • Reconstruction of the Tailings Storage Facility perimeter berm adjacent to the Main Landfill; • Construction of a perimeter berm between the Main Landfill and the TSF to separate the two facilities and create a boundary for landfilled waste; • Development of a drainage ditch between the two facilities to drain the standing water and prevent surface water run-on from contacting the waste;  • Placement and grading of cover soil over exposed waste within the Main Landfill; and • Placement of a temporary geomembrane cover over the filled area at the end of each construction season. Following British Columbia Ministry of Environment and Climate Change (MOE) review of the TAR, an amendment to Permit PR-7927 was issued on 31 May 2018.  As part of the Permit Amendment Application process THREAT was consulted and requested to provide input into the design, operation and monitoring requirements of the landfill.   Construction of the Phase 1 portion of the landfill was initiated during the 2018 field season.  Construction challenges existed in the form of: • Snow, ice and water accumulation present in much of the Main Landfill area; • Water flowing into the Main Landfill area from the TSF; • High winds in the alpine, mountain top environment; • Limited heavy equipment available to conduct the required engineered earthworks; • Aged equipment, left from previous mine operation with limited productivity, especially for hauling • Many competing priorities on site for use of the available equipment; and 42nd Annual BC Mine Reclamation Symposium  Challenges and Solutions to Meeting Indigenous and Stakeholder Mine Closure Objectives in a Remote, High Alpine Environment     • Limited opportunity to bring additional personnel, equipment and materials on site due to remote, heli-portable access. Because of the above challenges, engineering and construction at the site could not be conducted in a traditional Owner/Engineer/Contractor relationship.  Nor could work be tendered or issued for proposal as is typical for construction projects.  As such, SnipGold acted as both Owner and Contractor, Wood as Engineer, and equipment operators were hired directly from the Tahltan Development Corporation.  All parties needed to work cooperatively and together to achieve the annual reclamation objectives in the face of significant adversity. During the first few days of construction it became apparent that the Main Landfill could not be constructed as originally designed due to several of the challenges described above.  For example: construction of perimeter berms was not possible with the existing equipment, surface water flow direction needed to be reversed adjacent to the TSF due to previous dam construction practices, conventional anchoring of temporary geomembrane was not possible due to severe wind uplift, and a variety of other minor items.  This necessitated significant field engineering, which was fortunately possible as Wood’s lead landfill engineer was on site for a project start up meeting and was able to make major design changes during the first few days of construction.  This was only possible because the Owner was also the Contractor and could be flexible with resource allocation, schedule and other site priorities.  Because of this flexible approach, the Main Landfill was successfully constructed and all reclamation priorities for 2018 were completed. PAG/Waste Rock Closure options analyses were conducted to evaluate the best approach for management of the PAG waste rock material located at the portals, Mill Building area and along the Airstrip.  Among the options considered, the co-disposal option with water cover was selected.  This option includes excavating, transporting and placement of approximately 87,500 m3 of PAG-waste rock within the Tailings Storage Facility.  Sufficient water cover will be maintained to restrict ingress of oxygen and development of metal leaching/acid rock drainage (ML/ARD).  To minimize the cost of transporting non-PAG waste rock to the TSF additional delineating of PAG waste rock will be conducted in 2019.     Figure 6: Johnny Mountain Mine Main Landfill Conceptual Design 42nd Annual BC Mine Reclamation Symposium  Challenges and Solutions to Meeting Indigenous and Stakeholder Mine Closure Objectives in a Remote, High Alpine Environment     Contaminated Groundwater Based on relatively low concentrations, groundwater contamination associated with hydrocarbons and metals will be remediated using a risk-based approach.  A preliminary quantitative risk-assessment (PQRA) scheduled for 2020 will be completed in support of this remedial strategy.   A detailed quantitative risk assessment (DQRA) may follow if risk thresholds identified by the PQRA are exceeded.  A long-term groundwater quality monitoring program may also be implemented to document natural attenuation of contaminants, particularly hydrocarbons in groundwater.  Additional groundwater quality monitoring will be conducted to establish baseline metal concentrations for the site as elevated concentrations maybe associated with naturally occurring mineralization of soil.  The groundwater monitoring network installed in 2017 includes both near-field and far-field sentinel monitoring wells which serve to document baseline metal levels and to also document contaminant fate and transport, and invoke mitigative remedial options as may be required.  CLOSURE The reclamation of a mine site should be preceded by the development of a PEP.   The PEP should address the requirements of the approved closure plan however, while also meeting stakeholder requirements including applicable provincial and federal regulations. The success of the PEP will depend on a full appreciation/accounting of project related risks and challenges which for remote mine sites in northern British Columbia, includes indigenous peoples concerns, site physiological conditions, climate and site access.   For the JMM site, the PEP was developed one-year in advance of initiating reclamation activities.  The initial year of reclamation involved an extensive investigation to address data gaps in groundwater and soil environmental conditions.  To this end, SnipGold was able to implement a reclamation plan that was cost-effective and should lead to the successful reclamation of the JMM Site. REFERENCES Amec Foster Wheeler. 2017a. 2017 Project Execution Plan Johnny Mountain Mine Reclamation. Prepared for SnipGold Corp. May 2017.  British Columbia Ministry of Environment (BC MOE). 2015a. Protocol 21 for Contaminated Sites – Water Use Determination. 15 December 2015. Fillatre Miller E et al 2019. Mining Reclamation 101: Acquisition to Reclamation Former Johnny Mountain Mine Case Study BC TRCR Fletcher, B.A. and Hiebert, S. 1990. Geology of the Johnny Mountain Area NTS 104B/11E. Open File Map 1990-19 (2 Sheets). British Columbia Ministry of Energy, Mines and Petroleum Resources.  Greenwood Environmental. 2015. Annual Reclamation Report for 2015 Mines Act Permit, Number: M-178. Price, William and Yeager, D.A. 2004. ML/ARD Assessment and Mitigation at the Johnny Mountain Gold Mine MEND Report 9.1a. Mining Association of Canada and the Mining and Mineral Sciences Laboratory of Natural Resources Canada.  42nd Annual BC Mine Reclamation Symposium  Challenges and Solutions to Meeting Indigenous and Stakeholder Mine Closure Objectives in a Remote, High Alpine Environment     Rescan Tahltan Environmental Consultants (RTEC). 2017a. ISKUT PROJECT, 2016 Johnny Mountain Aquatic Characterization Report. Prepared for SnipGold Corp. Rescan Tahltan Environmental Consultants (RTEC). 2017b. ISKUT PROJECT, Annual Reclamation Report for 2016: Mine Act Permit Number M-178. Prepared for SnipGold Corp. SnipGold Corp. 2015. Johnny Mountain Mine Closure Management Manual.  Sperling Hansen. 2012. Johnny Mountain Landfill Preliminary Design Report. Prepared for SnipGold Corp. Woznow D.P. and D.A. Yeager. 1999. Closure Plan for The Johnny Mountain Gold Mine, Reclamation Permit No. M-178. International Skyline Gold Corporation.   

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            data-media="{[{embed.selectedMedia}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.59367.1-0391928/manifest

Comment

Related Items