British Columbia Mine Reclamation Symposium

Opportunities to incorporate mine closure into mine planning Ames, S. E. 2015

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

Item Metadata

Download

Media
59367-Ames_S_Opportunities_to_incorporate_mine_closure.pdf [ 702.89kB ]
Metadata
JSON: 59367-1.0305863.json
JSON-LD: 59367-1.0305863-ld.json
RDF/XML (Pretty): 59367-1.0305863-rdf.xml
RDF/JSON: 59367-1.0305863-rdf.json
Turtle: 59367-1.0305863-turtle.txt
N-Triples: 59367-1.0305863-rdf-ntriples.txt
Original Record: 59367-1.0305863-source.json
Full Text
59367-1.0305863-fulltext.txt
Citation
59367-1.0305863.ris

Full Text

Mine Closure 2015 – A.B. Fourie, M. Tibbett, L. Sawatsky and D. van Zyl (eds) © 2015 InfoMine Inc., Canada, 978-0-9917905-9-3 Mine Closure 2015, Vancouver, Canada 1 S.E. Ames  AMES Mine Closure and Reclamation International, Canada   Most early mine operations did not include closure planning. When closing an abandoned mine, operators are faced with all of the problems that have been left, for example, old equipment and structures, contamination, unstable landforms and a lack of soil to reclaim the disturbed areas. Closure planning is now a requirement for both new and operating mines around the world. Its focus is on meeting the end land use objectives and regulatory requirements. Early closure planning at the mine development stage provides an opportunity to design landforms for successful closure and more easily meet the end land use objectives of the site while complying with regulatory requirements. These opportunities may be lost if closure planning is delayed. For example, the options for reclaiming waste rock piles may be reduced if planning is carried out later in a project. Early planning can reduce future closure costs by minimising rehandling of mine wastes. This also affects bonding costs. Innovative approaches for closure that provide long-term site and environmental sustainability at the post-closure stage increase the opportunity for regulatory and stakeholder approval, allowing a project to be permitted sooner. Early closure planning also enables coordination of all aspects of mine development that will allow the closure of the project to occur as planned. There are challenges in coordinating engineers, wildlife biologists, soil scientists and water specialists to develop a cost-effective and sensible plan for closure. Inputs and considerations from these different disciplines in mine planning result in a closure plan that is generally based on current conditions of the mine site and ensures there is more opportunity to return the site to its former condition, as much as practical. Sometimes, temporary or early closure is required. For example, some early infrastructure may be buried by later infrastructure so if a project is stopped, the closure requirements will be different than if the project proceeded. Early planning for these unexpected situations may also affect closure and bonding costs.  This paper discusses opportunities that were realised when mine planning occurred early in a project and the challenges and approaches that were encountered when closure planning occurred during operations and when a site had been abandoned. These approaches can be used in mines in Canada and all over the world. Closure planning allows the closed mine site to partially disappear into the surrounding environment, as mines are only borrowing the site for a period of time. Mine closure planning was not considered over the last several hundred years of mining and therefore, there are abandoned mines all over the world. Mine closure planning has become mandated recently in many jurisdictions. The concept of closure and reclamation planning, however, is broad and variable as there are no international standards. Closure planning often includes planning for reclamation, which is generally considered to mean revegetation. Closure and reclamation plans can range from a single paragraph to a detailed plan where species are identified and seeding rates are included. The inclusion of a statement that the operator will close and reclaim a site is often all that is required to get a project permitted. Therefore, there is inconsistency regarding the meaning of mine closure and reclamation planning and the requirements for obtaining a permit. Often the benefits of a mine in a jurisdiction are so critical that environmental considerations are overlooked to some extent. Often there are fewer requirements for closure planning in a location where mining is a new industry and the experience of the regulators is more limited than in a jurisdiction where several mines have operated. In some regions of the world, revegetation is less challenging than in other areas and therefore, reclamation is less of an issue. The concept of a closure and reclamation plan is not firm, and the stage of a project when the closure and reclamation plan should be developed is also not clear. In British Columbia (BC), Canada, there are clear and documented guidelines for mine closure Opportunities to incorporate mine closure into mine planning S.E. Ames 2 Mine Closure 2015, Vancouver, Canada and reclamation and when this should occur. Closure and reclamation planning is required for new projects and the expansion of existing projects. However, familiarity and comfort with these guidelines are limited as new mines and expansions of existing mines are infrequent. This paper describes the regulatory framework that drives closure and reclamation planning in BC and the opportunities that can be achieved in reaching the goals of closure and reclamation when mine planning occurs early in the project. Planning for closure and reclamation is less creative when this planning occurs during operations or when a site had been abandoned. The principles underlying the various approaches discussed can be adopted as best management practices across the world with or without a regulatory framework in place. In BC, mine closure and reclamation planning is mandated under the BC Mines Act (1996) and the Health, Safety and Reclamation Code (the Code) for Mines in British Columbia (British Columbia, 2008). Closure and reclamation requirements are described in Section 10 of the Code. Closure planning is required for all infrastructures on a mine site, including waste dumps, major impoundments, water structures, openings, processing facilities and site roads.   The major drivers of reclamation in the Code include the following:  10.7.4. The land surface shall be reclaimed to an end land use approved by the chief inspector that considers previous and potential uses. 10.7.5. Excluding lands that are not to be reclaimed, the average land capability to be achieved on the remaining lands shall not be less than the average that existed prior to mining, unless the land capability is not consistent with the approved end land use.  … 10.7.8. … All surficial soil materials removed for mining purposes shall be saved for use in reclamation programs unless these objectives can be otherwise achieved. (British Columbia, 2008) In BC, waste dumps as well as other disturbed areas must be reclaimed.  An estimate of the total expected costs of closure and reclamation over the planned life of the mine, including the costs of long-term monitoring and maintenance, are also required as part of the development of the closure and reclamation plan.  The standards set out in the Code rely heavily on baseline studies and the requirement to develop the end land use objectives. Operators who fail to follow the Code in BC risk not receiving a permit. Other Canadian jurisdictions, such as Ontario, also have strict closure and reclamation requirements, as mandated in Regulation O. 240/00, Mine Development and Closure under Part VII of the Mining Act (Ontario, 1990).  Although the regulations vary from country to country and jurisdiction to jurisdiction, good planning will stand the test of time. It is important to note that regulations often become more stringent as government agencies revise their closure requirements due to increased experience and knowledge sharing. Many abandoned mines around the world have left great environmental impacts, which are noticed by the general public, who now scrutinise these kinds of projects and the decisions of the regulators more carefully. Approaches to closure and reclamation may become more uniform with the development of international standards.   As closure occurs at the end of operations, despite the requirement for closure and reclamation planning, detailed planning for closure and reclamation is often considered a low priority until the end of operations, when the end of the life of mine (LOM) is imminent. However, BC regulations require a detailed closure and reclamation plan to be developed as part of the Environmental Application, one of two major documents Case Studies Mine Closure 2015, Vancouver, Canada 3 required for a new mine project in BC. The second required document, the Mines Act Permit, must include more detail, including a detailed five-year plan.  There are also two earlier stages prior to the Environmental Application where closure and reclamation planning can be included in mine planning:   Preliminary feasibility (pre-feasibility) study   Bankable feasibility (feasibility) study  The pre-feasibility study, according to National Instrument 43-101 (NI 43-101), is a comprehensive study of the viability of a mineral project based on a range of components, including mining method; mineral processing; technical, legal, operating, economic and environmental factors; and financial analysis. The feasibility study includes similar considerations and serves as the basis for a final decision by a financial institution to finance a project. Geologists find and delineate the ore body; these specialists are often the owners of companies, particularly smaller mining companies. During the pre-feasibility and feasibility stages, company owners generally rely on engineering consultants for the design of the mine and the project in general. Several speciality engineering companies are often brought in to design different components of a project such as the waste rock dumps, the tailings storage facilities and the pit design. These specialists work on their specific tasks and may or may not come together. Frequently, as closure and reclamation planning are not at the forefront, mine planning in the pre-feasibility and feasibility stages may proceed in a direction that will not meet the Code. This can result in a large expenditures of effort and money that may require reversal and redesign of the mine plan, as described below.   This case study is related to the design of waste rock dumps. This project is located in an isolated, mountainous area with very narrow valleys and limited space for constructing the dumps. During the early mine planning stages, the waste rock dumps were therefore designed to occupy the smallest footprint possible because of the limited space. This required the dumps to be constructed by end dumping, which resulted in long, steep slopes at the angle of repose.   The proponent was not familiar with the Code, and planning proceeded without knowledge of the Code. The proponent and the waste rock dump engineers were not aware that waste rock storage dumps require reclamation in BC. The slopes of the proposed design were not only too steep for reclamation but their proposed location did not allow for resloping so that reclamation could be carried out later ( at the closure stage). The risk was that a permit would not be given with this plan. Therefore, the waste rock dumps had to be relocated and redesigned. This change was costly for the proponent. However, the cost to redesign the mine plan would have been greater if the mine plan was further advanced and other planned infrastructure had also required redesign and relocation.  The waste dumps were relocated and redesigned in the mine plan to incorporate the appropriate slope for reclamation. This reduced the requirement to reslope at the closure phase. The cost of resloping is very high, as resloping of long, high dumps requires rehandling of mine waste. Further, the cost for resloping would be incurred at the end of LOM, when there are no proceeds from ore sales. Further, the choice to delay resloping until closure can result in the company carrying large bonds throughout the LOM. Resloping at the end of mine life also delays closing of the site and presents an additional risk of increased inflation. By incorporating closure and reclamation planning in the early mine design, proponents can substantially reduce the size of the bond carried during operations and the interest on this bond, if it is borrowed.  The ability to reclaim the waste rock dumps is a requirement of the Code. However, the inclusion of early mine closure and reclamation planning in the development of the mine plan can also provide an opportunity to design unique end land uses. For example, for the case study described above, early input and planning meant that the design of the waste dumps was further manipulated to include multiple slope angles and Opportunities to incorporate mine closure into mine planning S.E. Ames 4 Mine Closure 2015, Vancouver, Canada engineered covers in selected areas that, coupled with unique revegetation prescriptions, could result in the development of a complex of various, unique wildlife habitats.  For this case study, baseline wildlife surveys indicated that this particular project location has important mountain goat, hoary marmot and grizzly bear habitat. These species are considered valued ecosystem components (VECs) in BC. It was recognised that some project components, including the waste rock dumps, would bury critical wildlife habitat. The early design of the waste rock dumps provided an opportunity to incorporate the potential for these wildlife habitats into the waste rock dump designs.  The closure and reclamation specialist worked with wildlife, terrestrial ecology and surface water specialists and waste dump engineers to develop a waste rock design for the mine plan that would accommodate these species. This involved incorporating escape terrain for mountain goats, which required the top of the waste dumps to be left steep at the angle of repose and absent of vegetation; including suitable vegetation such as grasses for mountain goat and hoary marmots at lower elevations; and developing grizzly bear habitat in the lower part of the dump (Figure 1). Mountain goat habitat includes both suitable vegetation for browsing and escape terrain, which is necessary because mountain goats are at risk of predation by grizzly bears. If the design included reclaimed slopes over the whole waste rock dump, mountain goat escape habitat would not have been possible. Not including the design for escape habitat for mountain goats could have represented a permit risk because of the importance of mountain goats at the site.  The mine plan required a contact water storage facility to collect metal leaching/acid rock drainage (ML/ARD) from the waste rock dumps and the overall site. The most appropriate location for this pond is at the base of the waste rock dumps. Because the contact water will not be suitable for wildlife consumption, the presence of this water storage facility presented a risk to wildlife and, therefore, a risk to obtaining a permit for the project. Solving this issue required the closure and reclamation specialist to work with the engineers to design the base of the slope above the water pond to reduce potential wildlife access to the contact water storage facility. To achieve this, the base of the waste rock dumps was designed to be very steep. This slope could not be reclaimed, and it would therefore not have any attractant vegetation. As a precautionary measure, attractant vegetation was planted upslope of the water storage pond to draw the wildlife away from the water storage facility. This reduced the wildlife habitat attraction of that portion of the dump, including the contact water storage facility.  The waste rock dump material is very coarse, and this property reduced the potential for natural revegetation due to the lack of fines, plant nutrients and water storage capacity for plant growth. The team planned for vegetation patterns that would provide for the unique end land use objective by including forest cover species above the steep, unvegetated slope that will provide less palatable vegetation and a physical impediment to animal movement (Forest B, in Figure 1). This design will direct the wildlife across the waste dumps toward better habitat (Forest, in Figure 1). The Forest habitat was designed to be suited to grizzly bears. The band of vegetation species above the Forest area provided marmot and mountain goat habitat, which was connected to the adjacent native habitat such that the mountain goats could travel across the high-elevation landscape on similar terrain and vegetation types. Similarly, the forest cover for grizzly bear habitat connected to the adjacent forest such that grizzly bears could also travel across the landscape at a similar elevation in a similar habitat.  Case Studies Mine Closure 2015, Vancouver, Canada 5  The attention paid to reclamation planning very early in the mine design increased the potential for the mining company to obtain a permit. Key critical wildlife species vary from country to country and climate to climate. With good early planning, the appropriate habitat for site-specific species can be achieved. Early closure planning also allows all aspects of mine development to be coordinated, which will allow the closure of the project to occur as planned. This type of planning makes it more likely that a project will be permitted by the regulators and supported by local governments and stakeholders.  The requirement to salvage soil for reclamation is a practice that results in successful reclamation in all parts of the world. Before the Code was established in BC, soils were generally buried by mine infrastructure such as waste rock dumps. The Code now ensures that soil salvage considerations are included in the development of the closure and reclamation plan included in the BC Environmental Assessment Application.  The assessment of the soils in the footprint area for reclamation purposes requires a review of the soil baseline information, including surficial materials, soil physical and chemical properties, and soil depth. Topography should also be considered, as suitable soils may not be accessible by heavy equipment such as dozers. The volume of suitable soil may also not be sufficient as waste rock dumps are mounded, constructed landforms with a greater surface area than their footprint.  A materials balance calculation is required to assess the amount of soil available for reclamation and the amount required. The depth of the soil cover is a function of the physical and chemical characteristics of the soils, climatic factors and the nature of the underlying materials. The decision regarding soil cover depth is often a compromise. Where there is insufficient soil for reclamation, overburden, if available, may be used to supplement the soil shortage.  Overburden is often considered a waste material. The requirement to salvage and stockpile soil and overburden for reclamation can be very costly, and this cost is incurred during the construction phase. The approximate cost to handle soil and overburden is generally not included in the pre-feasibility and feasibility studies, although these studies include economic analyses of a project.  Opportunities to incorporate mine closure into mine planning S.E. Ames 6 Mine Closure 2015, Vancouver, Canada Closure and reclamation plans describe the closure and reclamation of a mine site at the end of the LOM. However, a mine project can be terminated early, and the closure and reclamation plan developed for the end of the mine project may not be suitable for early closure. The amount of disturbance often increases as the project progresses. Many jurisdictions do not have a requirement to develop a specific detailed closure and reclamation plan for the early years of the project and, therefore, they may not be prepared for closure of the site if this occurs during an early stage. The BC Mines Act Permit application requires a detailed five-year plan for these early years of a project. In some mines, such as large open-pit mines, the infrastructure required in the early part of a project, such as muck pads and local sediment ponds and roads, may be buried by future infrastructure such as waste rock dumps. A detailed closure and reclamation plan for these early components will not be included in the LOM closure and reclamation plan as they will no longer be relevant.  The cost of closure and reclamation is required as part of the detailed five-year plan. This cost is also used to set the size of the financial bond the company must provide to the government. The government uses the bond requirement as a guarantee to ensure that the mine site can be closed and reclaimed in the event the proponent defaults or is no longer on the site. The goal of the BC government is to avoid paying for the cost of closing and reclaiming a mine site regardless of the stage of the project. Thus, the bond will vary over the LOM.  Closure and reclamation planning for an expanding operating mine can be challenging. In BC, the expansion of an existing operating mine also requires a Mines Act Permit for the expansion area. At one mine, there was an opportunity to remine a pit to extract additional ore. When the ore was first extracted, the waste rock dumps and tailings storage facility were placed on top of the native soil as reclamation was not a requirement at that time. The plan to reopen the pit includes constructing a new waste rock dump on top of the drained, former tailings storage facility and a second dump partly on an existing waste rock dump and partly on undisturbed land. The plan to place new infrastructure on existing mine waste is a good approach as it reduces the mine footprint. The placement of one of the waste rock dumps on previously undisturbed land will provide the first opportunity to salvage soil for reclamation for the operating mine.  The soils were assessed for reclamation as required by the Code. Salvaged soils must be stored often for the LOM, and the location of the stockpiles must be carefully considered to ensure that they are not disturbed by mining activities. In some instances, new land areas have to be cleared and levelled to store the stockpile. This increases the mine footprint and the amount of land that will ultimately have to be reclaimed. The greater the distance between the soil storage and the areas where they will be required for reclamation, the greater the costs to carry out reclamation. In this case study, the mining company recognised an opportunity to reduce haulage distance and avoid disturbing more land by stockpiling soils on top of existing, adjacent waste rock dumps.  The materials balance calculation indicated there was insufficient soil for reclamation of the new waste rock dumps. So the salvaged soil will be strategically used only on areas of the waste dumps that will result in the greatest opportunity for successful reclamation. Determining which portions of the waste rock dumps would be covered in soil involved several factors including adjacent land use. The general end land use objectives for the site are wildlife habitat, grazing and forest. As the expansion area infrastructure is predominantly located in a brownfield, it was determined that a strategic location for the soil would be on the parts of the waste rock dumps adjacent to native wildlife and forested habitat. Therefore, reclamation would increase the connectivity between the natural wildlife and forested habitat and the area reclaimed to forest and wildlife habitat. Aspect was another consideration in maximising the use of the soil. The site is located in a part of BC that has a dry, warm climate. It was decided that soils would not be spread on south facing slopes because plants on Case Studies Mine Closure 2015, Vancouver, Canada 7 these slopes are more susceptible to moisture stress than on other aspects. As well, because of the shortage of soil, soils would not be used on the portions of the new waste rock dumps that occurred adjacent to existing mine wastes or mining areas.  In this case study, there was an option to reclaim the other parts of the waste rock dumps, though with poorer quality material. Large amounts of overburden were removed from other parts of the mine site. This material will be used to cover the portions of the waste rock dumps that will not be soil covered. Although this is not an ideal approach, the regulators appreciate that a compromise is required when a mine has been operating without the early benefit of the Code requirements. Compromises such as this can be used in all locations to reclaim areas where there are insufficient soils for reclamation.  Closure and reclamation plans are required for operating mines in many jurisdictions. This may be related to the regulatory framework, or it may be required to provide the detailed closure and reclamation cost required for the development of the asset retirement obligation (ARO) of an operating mine. This is a legal obligation associated with retiring a tangible long-lived asset, and it requires a detailed mine closure and reclamation plan. The closure and reclamation plan for an operating mine is similar to a plan for a new mine in that each component of the mine and future components must be included. Governments also require closure and reclamation plans when operators close abandoned mines. Developing a closure and reclamation plan for an operating mine or an abandoned mine does not require costly baseline studies of wildlife, fisheries, terrestrial ecology, soils and terrain, hydrology and hydrogeology, such as those that would be required for a proposed mine, because the site has already been disturbed, as indicated in Figure 2. These mines require a detailed investigation of the mine site, including checks of all infrastructure such as leach pads, waste rock dumps, open pits, water treatment plants, fuel storage facilities, pregnant ponds, conveyor systems, tunnels and mill buildings.  The mine waste materials on a site also require laboratory analysis. Essentially, all components of a mine must be checked and contamination delineated and documented. Laboratory analyses may include acid base accounting (ABA) and may measure metals and hydrocarbons.  Opportunities to incorporate mine closure into mine planning S.E. Ames 8 Mine Closure 2015, Vancouver, Canada The closure of these sites is challenging and expensive, and there is little opportunity for reclamation. Site stability is a major consideration. For example, steep, long slopes are subject to erosion (Figure 3) and may require expensive resloping to achieve stability.   Governments all over the world are concerned about abandoned mines and the cost of clean-up. Safety of abandoned mines is a major concern, with openings presenting a risk to wildlife and people. Standard practices such as backfilling are common (Figure 4).   Many abandoned sites have complex histories that require extensive investigation. The long-term exposure of ML/ARD mine waste materials can result in contaminated water being released to the environment, as Case Studies Mine Closure 2015, Vancouver, Canada 9 shown in Figure 5. Contaminated water and land adjacent to sources of ML/ARD may require costly remediation and long-term water treatment.   The opportunities for standard closure and reclamation solutions are generally not available for abandoned mines. Closure and rehabilitation options often include expensive solutions such as geosynthetic liners and constructed barriers, ongoing water treatment and engineered wetlands. The lack of reclamation material may require the need for off-site borrow pits. Material transport is expensive, and the borrow pit areas must also be reclaimed.  The extent of disturbance and contamination of abandoned mines will continue to be a concern to governments and jurisdictions, as abandoned mine sites have resulted in extensive off-site contamination to neighbouring communities, reservoirs, drinking water and fish-bearing streams. The closure of these abandoned sites will be slow as they are expensive and the costs are often covered by governments.  The future of mine closure and reclamation planning will become more stringent and structured as regulators share information between jurisdictions and the expertise of technical experts increases. International standards are being developed that will aid jurisdictions with less stringent standards. Continued research on reclamation in areas such as in cold climates will result in revisions of the requirements for closure and reclamation plans and in new standards.  The Mount Polley tailing dam failure in BC in 2014 has resulted in an increased requirement to plan for infrastructure failures. The new rules state mining firms must consider the possibility of a tailings disaster and evaluate the environmental, health, social and economic impacts of an accident. This will likely result in a new section in a closure and reclamation plan that would include approaches for remediating the various potential failures and the costs associated with this remediation. In BC, because of the Mount Polley tailings dam failure, there will be a tendency to move away from traditional tailings storage ponds and potentially toward dry stacking of tailings. Dry stacked tailings will be easier to reclaim and will likely have a smaller footprint than traditional tailings ponds.  Opportunities to incorporate mine closure into mine planning S.E. Ames 10 Mine Closure 2015, Vancouver, Canada Mine closure and reclamation planning is site specific, and each site requires an approach that will be suited to the site, the nature of the operation and the regulatory framework. Early planning for mine closure and reclamation generally results in greater and more cost-effective opportunities for successful closure and reclamation of a site. Companies are only borrowing the site for a period of time, and early planning allows much of the site to be returned to a productive state. Good closure planning results in the support of regulators and stakeholders and can increase the opportunities to obtain a permit. Delays in receiving a permit can result in financial losses or termination of the mine project. Good planning also reduces bonding costs and the ARO, releasing more funds to create new opportunities. Closure planning during the operations phase can result in unsuccessful reclamation if landforms are not designed for reclamation and if the soil resource is buried under the mine infrastructure. Closure and reclamation become more costly as waste rock dumps or heap leach pad slopes require resloping at the end of mine life. This can greatly increase the cost of closure and the costs of bonds. This financial liability is carried through the operations phase. At this latter stage, large costs are incurred when mining is completed and the ore has been depleted.  Abandoned mines can be costly to rehabilitate, particularly if environmental contamination has migrated to the adjacent land and affects water quality, fish, wildlife and human health. Extra costs can be related to water treatment and the closing of a site without reclamation materials. The visible signs of mining activity are more difficult to remove as the natural resources are not available for reclamation. British Columbia (1996) Mines act, RSBC 1996, Chapter 293, Queen’s Printer, Victoria, British Columbia.  British Columbia (2008) Health, safety and reclamation code for mines in British Columbia, British Columbia Ministry of Energy, Mines and Petroleum Resources, Mining and Minerals Division, Victoria, British Columbia. Ontario (1990) Ontario regulation 240/00: Mine development and closure under Part VII of the act, Mining Act, RSO 1990, Chapter M.14.   

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}]}"
                            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:
http://iiif.library.ubc.ca/presentation/dsp.59367.1-0305863/manifest

Comment

Related Items