Muskeg River Mine Dedicated Disposal Area (DDA) Plan for In-pit Cell 1

Muskeg River Mine Dedicated Disposal Area (DDA) Plan for In-pit Cell 1 Updated: November 2010 Directive 74 Appendix C Requirement Approval: 8512D Submitted to

SHELL CANADA ENERGY MRM DDA PLAN-UPDATE NOV 2010 Table of Contents 1 INTRODUCTION... 1 2 DEDICATED DISPOSAL AREA (DDA) PLAN... 2 2.1 ENGINEERING DESIGN FOR THE MRM CELL 1 DDA STRUCTURE... 2 2.1.1 DYKE 1... 3 2.1.2 DYKE 2... 4 2.1.3 PITWALL... 4 2.2 OPERATING PROCEDURES FOR THE CONTAINMENT STRUCTURE AND DEPOSIT.. 6 2.2.1 Summary of CT Operating Premises for Cell 1 DDA... 6 2.3 TIMELINES FOR CONSTRUCTION, OPERATION, CLOSURE, CAPPING, FORMATION OF A TRAFFICABLE DEPOSIT AND FINAL LANDFORM DESIGN... 10 2.4 FORMATION AND CAPPING OF TRAFFICABLE DEPOSIT... 10 2.5 FINAL LANDFORM DESIGN... 11 2.5.1 Closure Drainage Design... 11 2.5.2 Reclamation Material Placement... 12 2.5.3 Revegetation Design... 12 3 PLANNED ANNUAL FINES CAPTURE IN CELL 1 DDA... 18 List of Tables Table 2.1: Dyke Fill Material Descriptions... 3 Table 2.2: Timeline Summary... 10 Table 3.1: Planned Annual Fines Capture in Cell 1 DDA... 18 List of Figures Figure 1.1: Layout of Dedicated Disposal Areas within Surrounding Area... 2 Figure 2.1: Dyke 1 Design... 5 Figure 2.2: Dyke 2 Design... 5 Figure 2.3: Pitwall Design... 6 Figure 2.4 Cell 1 DDA Operating View... 9 Figure 2.5 Cell 1 DDA Section... 9 Figure 2.4: Closure Landform Design and Drainage Features... 13 Figure 2.5: Reclaimed Dedicated Disposal Area Cross Section A A 1... 14 Figure 2.6: Reclaimed Dedicated Disposal Area Cross Section B B 1... 15 Figure 2.7: Reclaimed Dedicated Disposal Area Cross Section C C 1... 16 Figure 2.8: Reclaimed Dedicated Disposal Area Cross Section D D 1... 17 i

SHELL CANADA ENERGY MRM DDA PLAN-UPDATE NOV 2010 Concordance Table Appendix C Conditions 1 Engineering designs and operating procedures for the containment structure and the deposit, including details and timelines for construction, operation, closure, capping, formation of a trafficable deposit, and final landform design; 2 The planned rate and amount of fines captured within the deposit each year, and 3 A comprehensive plan on removal or remediation of segregated fluid tailings each year. Information Location Sections 2.1 2.5 Section 3 Section 2.2 ii

1 INTRODUCTION The Muskeg River Mine (MRM) Tailings Management Plan, as submitted in September 2010, utilizes one in-pit dedicated disposal area (DDA) for the period 2012 through 2015. This area is known as Cell 1. After 2016, it is expected that a portion of Cell 2B will be used for CT deposition as a DDA until the in-pit Cell 4 is available in 2019. DDA plans for Cell 2B and Cell 4 will be submitted at a future date. Additionally, the Atmospheric Fines Drying (AFD) area external to the mine pit, will act as a future DDA. This project is being managed under the test application process, and future DDA documentation will adhere to any requirements as set out by the ERCB. The location of the Cell 1 DDA within the Muskeg River Mine (MRM) is shown in Figure 1.1. Further details are provided in Section 1.6. The Cell 1 DDA is designed to be filled with composite tailings (CT) made by combining mature fine tails (MFT) from the external tailings facility at Muskeg River Mine, with coarse sand tailings (CST) produced as waste from the extraction process. Page 1 of 18

Figure 1.1: Layout of Dedicated Disposal Areas within Surrounding Area 2 DEDICATED DISPOSAL AREA (DDA) PLAN 2.1 ENGINEERING DESIGN FOR THE MRM CELL 1 DDA STRUCTURE The Cell 1 DDA is located west of the confluence of the Muskeg River and Jackpine Creek and north of the plant site. The facility is contained by: Dyke 1 along the northwest, Dyke 2 along the northeast and the pit wall along the remainder of the perimeter (see Figure 1.1). The footprint of the structure is approximately 1.8 km2 and provides 157.8 Mm3 of containment including freeboard. The Cell 1 DDA is the first in-pit cell to provide containment for tailings, and began fluid tailings storage in mid 2008. The cell currently contains fluid tailings that will require pumping to Cell 2A prior to Cell 1 being utilized as a DDA starting in Q3 2012. A perimeter dyke, currently in conceptual design stages, is required to separate tailings storage areas from the Muskeg River. Preliminary designs are planned for the end of 2011. Page 2 of 18

Dykes 1 and 2 reach a maximum elevation of 290 metres above sea level (masl), with an average height of 60m, and a maximum height of 85m (Figure 2.1 and Figure 2.2). Dykes 1 and 2 have a combined crest length of 3.5 km. The crest width is 50 m beginning in the southwest on the insitu pillar, narrowing to 35 m for much of the dykes before flaring out to 100 m at the east abutment. Table 2.1: Dyke Fill Material Descriptions Fill Type Type 1 Type 2 Type 4 Type 4w Type 5 G1 Toe Berm Fill C2 Clay Waste Seepage Blanket Description Good Quality Sandy Fill Good Quality Clayey Fill Moderate Quality Sandy Fill Moderate Quality Sandy Fill (Low Permeability Fill) Lower McMurray Clay Units General Waste Fill Clay Waste Fill 2.1.1 DYKE 1 The core of Dyke 1 is comprised of Type 4 fill (see Table 2.1 and Figure 2.1), with a downstream shell constructed of Type 1 fill with a slope of 4H:1V. The upstream shell is constructed of Types 1, 2 and G1 fills, and has a slope of 3H:1V. The toe berm on the upstream slope is built to an elevation of 250 m with a minimum 56 m crest. With several benches cut into the berm, an overall slope of approximately 5H:1V is achieved. Mitigation of seepage through Dyke 1 is managed by internal chimney drains and foundation cutoffs. A 2.5 m thick sand blanket underlies the downstream dyke wall (Figure 2.1). With the exception of the portions of Dyke 1 along the east abutment, French drains are installed at approximately 100 m spacing and are supplemented by perforated HDPE drainage pipes. Seepage discharge from the blanket and drains will be collected in a ditch at the toe of the dyke and flows to sumps where it will be pumped back into Cell 2A. Seepage through the foundation Page 3 of 18

on the upstream side is controlled by a 200 m long, 5 m thick seepage control blanket built from the toe of the upstream shell, under the toe berm and out into the cell area (Figure 2.1). 2.1.2 DYKE 2 The design of Dyke 2 has been modified as a requirement of the Tailings Management Plan submitted in conjunction with this Cell 1 DDA plan, but has not yet been approved by the Dam Safety Board. The modifications from previous designs are to accommodate fluid tailings storage in both Cell 1 (during CT consolidation) and Cell 2A (fluid tailings storage for CT production), where it was previously planned to have fluid tailings only on the upstream side of the dyke. The core of Dyke 2 is comprised of Type 4 and 4w fill (see Table 2.1 and Figure 2.2). The downstream and upstream shells are constructed of Types 1, 2 and 4 fill, with a toe berm constructed of Types 1, 2, 4, 4w and G1 fill at the toe of the upstream shell. The upstream dyke wall has a slope of 4H:1V including the toe berm and several benches, and the downstream has an overall slope of 4H:1V (Figure 2.2). Seepage through Dyke 2 is managed by a cutoff under the dyke core, and a 200 m long, 5 m thick seepage control blanket built from the toe of the upstream dyke out into the cell area (Figure 2.2). 2.1.3 PITWALL The pit wall is divided into two sectors with different overall slopes (Figure 2.3). Sector 1 includes the southwest pillar, upon which approximately 1.5 km of Dyke 1 is founded. The overall highwall slopes along this sector are 3.1H:1V. Sector 2 comprises of the portion of the pit wall north of the plant approximately 3 km in length and offset 110 m from the Muskeg River. Overall highwall slopes in this sector are 3.5H:1V. Highwall slopes are controlled by the potential for deep-seated failures through the LM2 and paleosol. Page 4 of 18

Figure 2.1: Dyke 1 Design Figure 2.2: Dyke 2 Design Page 5 of 18

Figure 2.3: Pitwall Design 2.2 OPERATING PROCEDURES FOR THE CONTAINMENT STRUCTURE AND DEPOSIT 2.2.1 Summary of CT Operating Premises for Cell 1 DDA Full details of the tailings engineering scheme for the Muskeg River Mine can be found in the Tailings Management Plan submission that addresses ERCB Directive 074 Appendix E requirements. To produce CT, MFT from the ETF are recovered and mixed with coagulant (alum) and CST from the tailings plant. The resulting mixture is transferred to the Cell 1 DDA. Release water produced in the cell is reclaimed to Cell 2A before being returned to the ETF. To provide an adequate deposition slope, CST will be placed in the DDA prior to start of CT deposition during the period 2010 and 2011. Page 6 of 18

Any fluid tailings that segregate from the CT deposited in the Cell 1 DDA will be pumped as fluid fine tailings to Cell 2A. Through the reclaim and clarification process of Cell 2A and the External Tailings Facility (ETF), these fluid tailings will be recycled back into the CT or AFD production processes. Any material not meeting the sand to fines ratio (SFR) of CT within the Cell 1 DDA will be remediated in place such that it meets the strength criteria required by Directive 074. Remediation in place of CT deposits not meeting the strength requirements as set out in D074, could include, but are not limited to, installation of wick drains, use of mechanical equipment means to promote dewatering and drying, and placement of sand layers to promote consolidation and fluid drainage. 2.2.1.1 CT Stream Management CT production will be monitored continuously with the aim of ensuring that material is produced that meets the expected constitution for CT. Cell 1 will be developed with specific areas that allow for short-term deposition of varying CT materials. Various factors including sand-to-fines ratio and fines over fines plus water, will be monitored to ensure CT is produced as designed. If CT production is being produced on-spec, the CT mixture is to be deposited on the east side of Cell 1 along the on-spec CT beach. If the CT production is determined to be falling into a transition zone and becoming off-spec, the CT product will continue to be deposited along the on-spec CT beach with immediate operations focus on improving the CT production quality. The amount of time spent operating in the transition zone will be minimized. If the CT production becomes off-spec, or continues in the transition zone for an extended period, the CT product will be deposited along the off-spec beach within Cell 1. If the product is Page 7 of 18

to be off-spec for more than a one 12-hour shift, alternate disposal areas will be considered, including the ETF or switching to alternate production lines away form Cell 1. 2.2.1.2 CT Deposition Methods Both sub-aerial and sub-ct methods of CT deposition are considered as viable deposition methods. Currently the sub-aerial method is being considered in the CT design. Sub-CT opportunities will continue to be investigated and it is likely that a combination of both methods will be used. The most critical element with sub-aerial deposition is to ensure that the CT is not discharged into freestanding water, as this will promote fines segregation from the CT deposit. Irrespective of the deposition methods chosen, the CT must not be deposited into free standing water and sub-aerial beaches should be maintained as long as practical. Consequently, Cell 1 will be aggressively dewatered. The objective is to introduce the CT slurry just below the surface of the CT discharge pool and to have the slurry flow to distal points in shallow meandering channels in a sub-aerial deposition mode. The absence of pooled water prevents dilution of the carrier fluids and subsequent resuspension of the flocculated fine mineral solids during deposition. It is preferable to have multiple CT discharge points so that localized shear of the CT slurry during discharge and deposition is minimized. Page 8 of 18

N Fluid to Cell 2A Fluid Collection Pool Off-Spec Beach (CST, WT, off-spec CT) CST, WT, off-spec CST spigot and flushing area Off-Spec Beach (CST, WT, off-spec CT) Cell 1 on-spec CT CST and CT Spigot CT CT or CST Current CST 2 line Figure 2.4 Cell 1 DDA Operating View Figure 2.5 Cell 1 DDA Section Page 9 of 18

2.3 TIMELINES FOR CONSTRUCTION, OPERATION, CLOSURE, CAPPING, FORMATION OF A TRAFFICABLE DEPOSIT AND FINAL LANDFORM DESIGN Table 2.2 provides a summary of the timelines established for planned construction, operation and closure of the MRM Cell 1 DDA. Specific details concerning construction and operation of Cell 1 DDA containment are provided in Sections 2.1 and 2.2, and for closure and reclamation in Sections 2.4 and 2.5. Table 2.2: Timeline Summary Start Date End Date Construction Preparation of Dyke 1 2005 2012 Preparation of Dyke 2 2008 2012 Preparation of Dyke 1i 2008 2008 Operations MFT and TT deposition into Cell 1A 2008 2011 Cell 1 CST deposition 2010 2018 1 Cell 1 CT deposition 2012 2016 Cell 1 fluid removal 2010 2016 Reclamation Completion of tailings deposition n/a 2016 CST layer deposition 2017 2018 Drainage piping into CST surface trafficable tailings surface construction 2018 2023 Overburden capping and drainage contouring 2024 2026 Reclamation coversoil placement 2026 2028 Nurse crop coverage and cap settlement 2028 2030 Revegetation 2030 2033 Monitoring 2033 TBD Note 1: CST is used in the DDA after CT start-up to create the operational working benches for CT deposition 2.4 FORMATION AND CAPPING OF TRAFFICABLE DEPOSIT Completion of tailings deposition and pumping of fluid tailings to Cell 2A is anticipated in 2016, followed by one year of CST deposition to an average depth of 5 m across the CT surface. CST deposition will be accompanied by installation of a pipeline system to ensure positive drainage Page 10 of 18

within the sand layer, such that the water table is drawn down and further capping activities are supported. Deposit strength required to allow a trafficable surface is anticipated by 2024. Overburden sourced from stripping operations in Cells 7 and 8 and possibly stockpiled on the surface of Cell 2B (pending capping operations) will be placed onto the trafficable CST surface to an average thickness of 3 m. The overburden cap will be contoured to grade to the adjacent dyke walls to provide channels for drainage and to supply mesotopographical features for reclamation activities. Cross sections showing typical overburden depths along drainage channels and at high and low elevations on the Cell 1 DDA surface are provided in Section 2.5. Overburden capping activities are scheduled to occur between 2024 and 2026 (see Table 2.2) to cover the 1.8 km2 surface area of the DDA. 2.5 FINAL LANDFORM DESIGN As the Cell 1 DDA is part of the larger northeastern drainage catchment area, reclamation activities and drainage features have been adapted to provide an operational reclamation plan until such time as the surrounding tailings cells and dyke walls are complete and the closure drainage plan for the entire area can be integrated. 2.5.1 Closure Drainage Design The closure drainage plan for the northeastern drainage catchment at Muskeg River Mine includes a drainage system linking a series of in-pit cells to a future pit lake. Until closure of the northeastern area, the drainage plan has been modified for the Cell 1 DDA area, to drain surface water northwest towards the adjacent Cell 2 area (Figure 2.4). In this way, drainage from the Cell 1 DDA will be designed to expand to the drainage network across the remainder of the area at closure, but will be maintained within a closed-loop area while adjacent in-pit cells remain in operation. Page 11 of 18

Overburden capping materials will be contoured to provide appropriate channel morphologies, as described in detail in the Muskeg River Mine Expansion ERCB application (2005) and shown in cross-section in Figures 2.5 to 2.8. It is anticipated that the overburden-capped DDA will settle by up to 2 m over time, and provide micro-topographical variation on the top surface. Ecosites that naturally incorporate limited low-lying wetlands have therefore been planned for revegetation activities. 2.5.2 Reclamation Material Placement On completion of overburden capping, reclamation materials will be placed according to prescribed replacement depths within EPEA Approval No. 20809-01-00. Reclamation material will be direct placed from salvage activities in northern pit areas, or from Reclamation Material Stockpiles located close to the Cell 1 DDA. An average of 20 cm of upland surface soil and 30 cm of upland subsoil will be placed over the overburden capping materials. These upland soils will be either medium or coarse-textured depending on the ecosite planned for the location (see Revegetation Design below). Cell 1 DDA surface areas adjacent to drainage channels and in flat areas will have 20 cm of coarse-textured upland surface soil and 30 cm of medium-textured subsoil placed in areas designed for g1 ecosites. Peat-mineral mix to a depth of 30 cm will be placed on the banks of drainage channels. 2.5.3 Revegetation Design Creation of the channel areas also provides adjacent raised hummock areas that will be used for upland ecosite development in the reclamation plans (Figure 1-7 to 1-9). It is anticipated that given the shallow gradient on the surface of the Cell 1 DDA area, most of the areas around the drainage channels have the potential to remain moist and have been designed as g1 ecosites, with areas of c1 in hummock areas and h1 adjacent to drainage channels (Figures 2.6 to 2.8). Page 12 of 18

Areas around the periphery of the top surface and on the top of the dyke walls have been designed as d ecosites with an area of c ecosite on the potentially drier south-facing top slope (Figures 2.4 and 2.8). Figure 2.4: Closure Landform Design and Drainage Features Page 13 of 18

Figure 2.5: Reclaimed Dedicated Disposal Area Cross Section A A 1 Page 14 of 18

Figure 2.6: Reclaimed Dedicated Disposal Area Cross Section B B 1 Page 15 of 18

Figure 2.7: Reclaimed Dedicated Disposal Area Cross Section C C 1 Page 16 of 18

Figure 2.8: Reclaimed Dedicated Disposal Area Cross Section D D 1 Page 17 of 18

3 Planned Annual Fines Capture in Cell 1 DDA Planned fines capture in the MRM in-pit Cell 1 DDA is as outlined in table 3.1 and is consistent with the supplied numbers in the 2011 MRM Annual Tailings Management Plan (D074 Appendix E) submitted in September 2010. Table 3.1: Planned Annual Fines Capture in Cell 1 DDA MRM Fines Sequestered in DDAs Cell 1 DDA Year CT Deposit (Mt) 2011 0.0 2012 2.1 2013 4.0 2014 3.6 2015 4.0 2016 4.5 A full fines balance is available within the report submitted on September 30, 2010, in support of Directive 074 - Appendix E: Muskeg River Mine Annual Tailings Management Plan 2011 - Tables 3.7 and 3.10 Page 18 of 18