Preliminary Mine Site Water Management Plan Sukunka Coal Mine Project Prepared for: Glencore 650 West Georgia Street Suite 710, PO Box 11611 Vancouver, BC V6B 4N9 Attention: Bryan Tiedt Prepared by: Knight Piésold Ltd. 750 West Pender Street Suite 1400 Vancouver, BC V6C 2T8 Final Rev. 01 123110482 June 28, 2015 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Table of Contents June 28, 2015 Table of Contents ABBREVIATIONS ....................................................................................................................... III 1.0 1.1 1.2 1.3 1.4 INTRODUCTION ............................................................................................................. 1 PROJECT LOCATION ......................................................................................................... 1 PURPOSE AND SCOPE ...................................................................................................... 1 PERFORMANCE OBJECTIVES ........................................................................................... 1 REGULATORY FRAMEWORK ............................................................................................. 1 2.0 2.1 ENVIRONMENTAL CONSIDERATIONS ........................................................................... 1 HYDROMETEOROLOGY .................................................................................................... 2 2.1.1 Extreme Rainfall Events .................................................................................. 2 WATERSHEDS ...................................................................................................................... 4 2.2 3.0 3.1 3.2 3.3 ENVIRONMENT PROTECTION MEASURES ...................................................................... 4 WATER MANAGEMENT OBJECTIVES ............................................................................... 5 BEST MANAGEMENT PRACTICES...................................................................................... 5 3.2.1 Collection Ditches .......................................................................................... 6 3.2.2 Diversion Ditches............................................................................................. 6 3.2.3 Energy Dissipaters ........................................................................................... 6 3.2.4 Slope Drains ..................................................................................................... 6 3.2.5 Waterbars ........................................................................................................ 7 3.2.6 Temporary Diversion Structures..................................................................... 7 3.2.7 Sediment Basins and Sediment Control Ponds .......................................... 7 3.2.8 Flocculent Addition ........................................................................................ 7 WATER MANAGEMENT MEASURES .................................................................................. 8 3.3.1 Preliminary Mine Site Water Management Plan Overview ...................... 8 3.3.2 Description of Water Management Measures ........................................... 8 3.3.3 Water Management Design Elements ...................................................... 15 3.3.4 Water Management Measures by Project Phase.................................... 16 4.0 4.1 4.2 MONITORING PROGRAM ........................................................................................... 18 MONITORING ................................................................................................................... 18 FOLLOW-UP AND ADAPTIVE WATER MANAGEMENT STRATEGY ................................ 19 4.2.1 Flocculants Use to Aid Settling .................................................................... 19 5.0 REFERENCES................................................................................................................. 20 LIST OF TABLES Table 2.1-1 Table 3.3-1 Table 3.3-2 Table 3.3-3 Table 3.3-4 Table 3.3-5 Intensity-Duration-Frequency Values ........................................................... 3 Catchment Areas of Key Water Management Features ....................... 15 Design Criteria ............................................................................................... 16 Construction Water Management Measures........................................... 17 Operations Water Management Measures ............................................. 17 Closure Water Management Measures .................................................... 18 i PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Table of Contents June 28, 2015 LIST OF FIGURES Figure 3.3-1 Figure 3.3-2 Figure 3.3-3 Figure 3.3-4 Sukunka Project Layout ............................................................................... 10 North Collection Channel Typical Section In Rock Cut .......................... 12 North Collection Channel Typical Section In Overburden ..................... 13 North Collection Channel Typical Section In Fill....................................... 14 ii PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Abbreviations June 28, 2015 Abbreviations BC British Columbia BMP best management practice CHPP coal handling and processing plant EC Environment Canada KPL Knight Piésold Ltd. LAA local assessment area masl metres above sea level MOE Ministry of Environment NSCP North Sediment Control Pond PDA Project development area PMP probable maximum precipitation SCP sediment control pond SSCP South Sediment Control Pond the Project Sukunka Coal Mine Project WMP Water Management Plan WSCP West Sediment Control Pond iii PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Introduction June 28, 2015 1.0 Introduction 1.1 PROJECT LOCATION The Sukunka Coal Mine Project (the Project) is located southeast of the Sukunka River and northwest of Bullmoose Creek, within the Peace River Regional District. The mine site is located within the Skeeter Creek and Chamberlain Creek watersheds, which are tributaries of the Sukunka River. 1.2 PURPOSE AND SCOPE This report outlines the preliminary mine site Water Management Plan (WMP) for the Project to support the environmental assessment application. The WMP includes information for the construction, operations and closure phases of the Project. The WMP, and its components, will inform the development of other Environmental Management Plans. This plan is submitted as part of the environmental assessment and is preliminary. A more detailed plan will be submitted as part of the Mines Act permit application. 1.3 PERFORMANCE OBJECTIVES The WMP describes the ability of the site water management infrastructure to contain, control, and convey runoff from snowmelt and rainfall, and in particular short duration extreme rainfall events (e.g., 1 in 10 year rainfall or 1 in 200 year rainfall events). Water management facilities are designed with two specific operating modes: 1) service conditions, which include day-to-day operations and 2) ultimate limit conditions, which include provisions for safely handling runoff during extreme hydrologic events. 1.4 REGULATORY FRAMEWORK This WMP is designed to minimize project related effects to the receiving environment, specifically receiving water bodies, and to meet commitments within the Application Information Requirement (AIR) document. The WMP may be updated in the future to address comments made during the environmental assessment review process, or to meet requirements outlined in applicable permits. 2.0 Environmental Considerations The Project is located in the Rocky Mountain Inner Foothills region. Topography in the region is typified by high elevation (1,600 to 2,000 m) mountain ridges and peaks and steep-sided slopes with relatively flat-bottomed valleys. The property is predominantly forested with lodgepole pine and occasional spruce, with stands of balsam poplar occurring in the lower or wetter areas of the property. Climate in the region is typified by cold temperatures and snowfall in the winter, and warm temperatures and both frontal and convective rainfall in the summer. 1 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Environmental Considerations June 28, 2015 Runoff from the project development area (PDA) will naturally want to flow downhill and into the aquatic environment surrounding the Project, specifically Chamberlain Creek and Skeeter Creek. In order to mitigate the potential for sediment entrainment or chemical loading to compromise water quality as it passes through the PDA and into the surrounding aquatic environment, best management practices (BMP) will be applied. 2.1 HYDROMETEOROLOGY The Project is located in a rain shadow of easterly flowing Pacific air coming over the main Hart Ranges of the Rocky Mountains, which creates a strong southwest to northeast precipitation gradient perpendicular to the mountain range alignment. The region can also be affected by low-pressure systems built up in central Alberta that can push considerable moisture westward into the area, resulting in orographic uplift and producing greater volumes of precipitation and runoff in higher elevation watersheds. Furthermore, cold dense Arctic air often stalls in the region in the winter bringing periods of intense cold and considerable snowfall (Demarchi 2011). Annual precipitation within the PDA varies strongly with elevation, and is estimated to range from 545 mm at low elevations (approximately 700 m) to 885 mm at high elevations (approximately 1,700 m). Annual runoff also varies with elevation, and it is estimated to range from approximately 226 to 550 mm between the elevations of 700 and 1,700 m. Hydrometeorological parameters are based on the results of the Project baseline watershed model, which has been developed using long-term synthetic precipitation and temperature records calibrated to long-term synthetic streamflow records. More information is provided in the Watershed Model Report (KP 2014a). The annual temporal distribution of runoff in the region is dominated by high flows during the spring (May–June) snowmelt freshet, followed by low flows for much of the remainder of the year, interspersed by periodic low to moderate magnitude rainfall-runoff events during the summer and fall. Peak flows typically occur during the freshet or during convective storms in the summer and fall, while low flows can occur either during the late summer or late winter. More information regarding local and regional hydrologic characteristics is provided in the Baseline Hydrology Report (KP 2014b). 2.1.1 Extreme Rainfall Events Annual extreme 24-hr rainfall values are summarized in Table 2.1-1. Daily precipitation data collected by Environment Canada (EC) at their Bullmoose Station between 1983 and 2002 were used to develop the return period values by applying the Extreme Value Type 1 (Gumbel) distribution to the data. This distribution may be expressed in the form of a frequency factor equation, as follows: X T = X + KT S XT = extreme event rainfall (mm) = mean rainfall for return period (mm) K T = frequency factor S = standard deviation for return period (mm) X 2 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Environmental Considerations June 28, 2015 The daily values were initially adjusted to 24-hr values using a multiplier of 1.13 (Hershfield 1961), before the data were scaled to the median site elevation of 1,200 m, from the Bullmoose Station elevation of 1,100 m, using an orographic adjustment factor of 5 percent per 100 m. The resultant values were checked against rainfall frequency information published by EC for Chetwynd and scaled to the Project using the same 5% per 100 m orographic factor. Both sets of values agree very well and are within 3 mm for all return periods presented below. The 24-hr probable maximum precipitation (PMP) event for the Project site was estimated to be 375 mm. The Hershfield equation and the mean and standard deviation of the Bullmoose Station 24-hr precipitation data, scaled to 1,200 m, were used to determine an appropriate frequency factor for use in the estimation of the PMP. The possibility of snowmelt combined with extreme rainfall must be considered when determining design flows. Table 2.1-1 Intensity-Duration-Frequency Values Return Period (years) 24 hour Rainfall (mm) 2 44 10 71 25 85 50 95 100 106 200 116 500 129 PMP 370 NOTES: The PMP was derived using standard world meteorological organization procedures (Hershfield 1965) / Hershfield Method. The PMP is effectively the largest conceivable storm event that could possible impact the site. The PMP value should be combined with an estimate of snowmelt when computing the probable maximum flood (PMF). Precipitation depths assume a median elevation of 1,200 m, which is the approximate mean elevation of the PDA. 3 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Environment Protection Measures June 28, 2015 2.2 WATERSHEDS Surface conditions, topography, soil cover and vegetation are key parameters that dictate how an area will respond to precipitation events. The hydrologic response (as represented by a hydrograph) varies both temporally and spatially depending on the combination of these basic parameters. • • • In general, a catchment with steep terrain, such as those typical of the project tenure area, tends to yield a quick response to rainfall events, whereas a catchment with flat or undulating terrain will exhibit a slower, more evenly distributed response. Common construction and open cut mining activities often flatten portions of the terrain and thereby reduce the rates of storm runoff. Soil cover has three key characteristics that affect the rate of runoff, which are soil type, perviousness and moisture content. A loose, coarse grained, pervious soil with a low moisture content will promote infiltration and diminish runoff; conversely, a dense fine grained soil with a high moisture content will inhibit infiltration and promote runoff. Typical construction and open cut mining activities tend to compact soils and reduce perviousness, and thereby increase the rates of storm runoff. Vegetation also plays an important role in regulating the rate of storm runoff. Plants affect hydrology through physiological processes (uptake of water and transpiration), as well as providing structure and stability to surficial soils that helps prevent erosion and soil loss. Catchments with little or no vegetation tend to experience more erosion and exhibit more rapid storm runoff than vegetated areas. Construction activities often reduce the vegetative cover of a portion of a catchment, thus increasing the rates of runoff and erosion. The Project is located within the Chamberlain Creek and Skeeter Creek watersheds. Both watersheds are characterized by deeply incised channels with steep valley sides consisting primarily of glacial till and exposed bedrock in their upper regions. Lower in their watersheds both creeks flow out into the relatively flat Sukunka River valley and discharge over deep alluvial fans and through a wetland prior to entering the Sukunka River. Both creeks lose sizeable amounts of surface runoff to the groundwater system as they cross the alluvial fans. 3.0 Environment Protection Measures The WMP describes how water will be controlled and managed during construction, operations, and closure of the Project. The objectives of the WMP are to manage water in a manner that provides sufficient water to support coal processing while minimizing contact water and the potential for storm flows to cause damage to mine structures, and thereby minimizing the potential for mining operations to cause adverse effects to downstream water quality. Water will be controlled in a manner that minimizes erosion in areas disturbed by construction and mine operation activities and limits the release of sediment or chemically laden water to the receiving environment. This includes diverting non-contaminated water around the mine area, collecting 4 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Environment Protection Measures June 28, 2015 surface water runoff from the mine area, constructing sediment control ponds, and managing water systems. The key facilities identified in the WMP are the: • • • • 3.1 Up to six open pits Waste rock stockpiles Collection ditches and diversion ditches Sediment control ponds WATER MANAGEMENT OBJECTIVES This section of the WMP describes the water management objectives and provides guidance for the control of all water originating from, or brought into, the mine site during the life of mine. The design criteria for the various sediment control elements required will be primarily based on the document titled “Guidance for Assessing the Design, Size and Operation of Sediment Ponds used in Mining”, as issued by the BC Ministry of Environment, Land and Parks (BC MOE-LP 2001). Water will be controlled in a manner that will minimize erosion in areas disturbed by construction and operation activities. The water management strategy is to minimize disturbance areas and implement BMPs as work progresses. The sources of water during construction and operation are as follows: • • • • • 3.2 Runoff from the Mine Site facilities Runoff from the un-diverted and un-disturbed catchment around PDA Fresh water from the Sukunka River Groundwater from the Open Pits Treated septic and grey water, in small quantities, from the mine wash house and other facilities BEST MANAGEMENT PRACTICES Experience and adaptive management are integral to the successful selection of the appropriate BMPs and the design and implementation of an overall WMP. Erosion control BMPs will be implemented prior to and during construction and will be maintained as needed through operations as needed to minimize erosion and sediment discharge into surrounding areas. Typical BMPs that could be implemented to meet the objectives of the WMP are: • • • • • • • • Runoff collection ditches Runoff diversion ditches Energy dissipaters Slope drains Water bars Diversion structures Sediment basins and sediment control ponds Flocculant addition 5 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Environment Protection Measures June 28, 2015 The above is not an exhaustive list of all possible BMPs. The final suite of BMPs to be implemented will be determined prior to construction and based on the need and appropriateness. Glencore will provide justification for why specific BMPs are selected. 3.2.1 Collection Ditches A runoff collection ditch intercepts contact water runoff and diverts it to a stabilized area where it can be effectively managed. Collection ditches are used within areas to collect runoff and convey it to appropriate sediment control measures. General locations and conditions may include: • • • Below disturbed slopes to divert sediment-laden water to control facilities At or near the perimeter of construction or operations activities to prevent sediment-laden runoff from leaving the site Above disturbed areas to prevent erosion before stabilization is achieved Collection ditches may be either temporary or permanent structures. Collection ditches will be inspected and maintained regularly to remove any blockages to flow (accumulated sediment, debris, etc.) that may occur. Flocculants will be added to contact water within the collection ditches at times when the sediment pond capacity and BMPs are predicted to be insufficient to manage TSS levels in the sediment pond effluent (15 mg/L TSS) as discussed in Section 4.2.1. 3.2.2 Diversion Ditches A diversion ditch is similar to a collection ditch but is designed for clean water diversion. A diversion ditch is a channel lined with vegetation, rip-rap, or other material designed for the conveyance of clean surface runoff to a receiving system, without causing erosion. 3.2.3 Energy Dissipaters Energy dissipaters are typically rip-rap lined plunge pools used to dissipate the energy of fast flowing water and prevent erosion of natural stream channels downstream. These structures are used in conjunction with diversion and collection ditches, and are typically located upstream of a receiving waterbody (e.g., stream, pond, lake, etc.), or within long diversion ditches to prevent erosion of the ditch itself. Energy dissipaters will be inspected and maintained regularly to remove any blockages to flow (e.g., accumulated sediment, debris, etc.) that may occur. 3.2.4 Slope Drains Slope drains consist of flexible tubing, a perforated pipe bedded in gravel, or a similar conduit and are required to convey concentrated runoff into the appropriate BMP structure when ditches are deemed impractical. Slope drains shall be sized according to estimates of peak flows, which are dependent on contributing drainage area. Slope drains will be inspected and 6 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Environment Protection Measures June 28, 2015 maintained regularly and any blocked or damaged parts will be cleaned, repaired, or removed and replaced. 3.2.5 Waterbars Waterbars serve to reduce sheet flow and surface erosion of areas of exposed soil and/or roads by diverting runoff towards a stable vegetated area or collection ditch. Spacing of waterbars will be field fitted based on the slope grade and general susceptibility of the surface to erosion. Waterbars must not direct runoff into a ditch that will channel water toward the watercourse unless the ditch is adequately prepared with check dams and armouring, where appropriate. Waterbars will require regular monitoring when subjected to frequent traffic crossings. 3.2.6 Temporary Diversion Structures A temporary diversion structure typically consists of sandbags stacked in a pyramid formation with a polyethylene sheet placed diagonally in between the bags. Temporary diversion structures are useful for diverting concentrated overland flow to an appropriate sediment basin or other BMP structure where it can be effectively managed. 3.2.7 Sediment Basins and Sediment Control Ponds A sediment basin is a temporary structure that is used to detain runoff from small drainage areas so that sediment can settle out. A sediment control pond (SCP) is an engineered structure designed for the life of mine that is similarly used to detain runoff from larger drainage areas to settle sediment. Sediment basins and SCPs are generally located in areas where access can be maintained for sediment removal and proper disposal. Sediment basins and SCPs are typically constructed at the end of collection ditches to detain sediment-laden runoff long enough to allow the majority of the sediment to settle out. A sediment basin can be created by excavating a basin, utilizing an existing depression, or constructing a dam across a channel or depression downslope from the work area. Sediment-laden runoff from the disturbed site is conveyed to the basin via ditches, slope drains, or diversion structures. The basin is a temporary measure, with a nominal design life of approximately six months, and is to be maintained until the site is permanently protected against erosion by vegetation and/or structures. The size of the temporary sediment basin is dependent on the size of the drainage area and the estimated rate of runoff. The exact location and final geometry of each basin should be field-fitted to integrate with the terrain to minimize disturbance. SCP design and placement is discussed in detailed in Section 3.3.2.3. 3.2.8 Flocculent Addition To assure sediment pond discharge suspended solids are within regulatory requirements, “potable” flocculants may be added to assist solids settlement. Control systems will be in-place to prevent overdosing flocculants in the run-off water collected. 7 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Environment Protection Measures June 28, 2015 3.3 WATER MANAGEMENT MEASURES 3.3.1 Preliminary Mine Site Water Management Plan Overview The project WMP is depicted visually on Figure 3.3-1. As shown, contact water will be minimized by the construction of diversion ditches upslope of Pits 1, 2 and 3. Water diverted in these ditches will be routed back to the main stream that it would have naturally discharged to via natural micro-tributaries. These micro-tributaries will be enhanced using rip-rap in order to safely convey the additional discharge. Contact water will be collected in downslope collection ditches and will be routed through a sediment basin or SCP prior to being discharged to the natural environment. Waste rock stockpile contact water will naturally flow downhill into the collection ditches, whereas pit contact water will flow via gravity in channels to the collection ditches or be collected in engineered low points in the pit and then be pumped to the collection ditches. Water collected in the South Collection Ditch will be routed through the south sediment collection pond (SSCP) prior to discharging to Chamberlain Creek. Water collected within the north collection ditch (NCD) and west collection ditch (WCD) will be routed through the north and west sediment control ponds (NSCP and WSCP) before being discharged to the Sukunka River via water pipe. The sediment basins and SCPs will settle out sediment the size of, or greater than, silt. Additional details regarding each major water management structure are provided in the following sections. 3.3.2 Description of Water Management Measures This section describes specific water management elements that will be utilized on site, and describes how they will be operated. The location of major surface drainage controls is shown on Figure 3.3-1. 3.3.2.1 Dewatering Dewatering of the excavation areas, including the open pit areas, will be accomplished by directing water to the collection ditches by open channel flow, or by the use of sump pits, wells, well-points and/or removable pumping stations. Runoff and seepage from construction and operational dewatering will be collected and discharged to the environment via down gradient collection ditches and SCPs. In addition, a portion of the contact water in Open Pit 1 may be pumped for use in the CHPP. 3.3.2.2 Collection and Diversion Ditches The WMP includes collection ditches to route water to areas within the Mine Site where it is required, or to divert contact surface runoff to downstream sediment basins or SCPs. Major collection ditches will be constructed around the downslope footprint edge of the Waste Rock 8 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Environment Protection Measures June 28, 2015 Piles and Open Pits, as shown on Figure 3.3-1. Collection channels will typically be lined with riprap or other engineered protection, when not cut in rock. The WMP includes diversion ditches to route upslope water around the PDA and into existing stream channels. Diversion ditches will be constructed upstream of the Open Pits on slopes conducive to ditch construction and will be similarly lined with vegetation, rip-rap or engineered protection, when not cut in rock. The location of all major diversion ditches are shown on Figure 3.3-1. The outlets of diversion channels will be fitted with energy dissipation structures and/or armoured with rip-rap to prevent erosion at points of confluence with natural channels. Both collection and diversion ditches will be designed in accordance with t the design criteria detailed in Section 3.3.3.1 below. The collection and diversion channels proposed in the WMP will be designed to minimize ditch bypass. Bypass of a collection or diversion channel results from the ability of the structure to capture and retain water from up-gradient areas. The following criteria and the factors influencing them are used to evaluate expected channel performance: • • • Capture Efficiency: The percentage of the total available flow from the up-gradient catchment that is captured by the channel. This includes surface water flow and groundwater flow. − The Capture Efficiency is expected to vary spatially along the proposed collection channels. − Capture Efficiency is estimated to be high in areas where the overburden is relatively thin and where sub-surface conditions promote groundwater discharge to surface. − The Capture Efficiency will be lower in areas where thicker overburden deposits allow for groundwater to remain in the sub-surface. Ditch Loss: The percentage of the flow in the channel that is not conveyed to the outlet, i.e. lost through seepage out of the channel. − Ditch loss is dependent on the hydraulic conductivity of the channel lining for lined channels or surficial material for unlined channels Net seepage capture efficiency: The overall efficiency considering both capture efficiency and the ditch loss. The capture efficiency of the proposed channels varies spatially depending on the thickness of surficial materials along the channel alignment. Sections of the channel constructed in bedrock cut will exhibit relatively high Capture Efficiency while those overlying thick surficial overburden deposits or fill are expected to have lower capture efficiency due to groundwater bypassing under the channel. The range of capture efficiency values is expected to vary locally between approximately 65 and 95 percent. 9 ! ! 588000 590000 592000 ± ! Sukunka River 6126000 110 0 ! 13 00 ! 13 00 14 00 ! ! ! 900 6126000 586000 ! 584000 13 00 ! 6124000 A ! ! 12 00 ! ! k a River ! 12 00 12 00 ! A ! Suk un ! ! 0 90 ! ! ! ! ! ! ! Ì ! ! ! ! ! ! ! ! ! Skeeter Creek ! ! Ì Ì Ì Ì Ì Ì 6122000 ! 6122000 ! Pit 04 ! A 1100 ! ! Pit 01 ! 0 70 ! 16 00 ! Sukunka River ! ! A ! " 6120000 ! 6120000 ! Pit 05 A A Pit 02 1700 0 80 Pit 06 Ch am be rl ain A Cr ee 6118000 6118000 k 00 13 Pit 03 13 00 00 13 Camp Options < Camp Option 1 Camp Option 2 1700 1200 0 18 0 1300 Mt. Chamberlain (1800 m) # 00 18 CHPP Option 1 Option 2 17 00 Haul Road Options Option A 18 00 1800 A 13 00 CHPP 0 12 0 1600 Option B A Option E 0 1 2 3 km " 584000 # AA 16 00 1:40,000 12 00 " 586000 Mountain Diversion Ditch Conceptual Open Cut Pit A Oil & Gas Well Collection Ditch Conceptual Waste Stockpile " Oil & Gas Facility HDPE Pipe Explosives Reload Facility Mine Infrastructure Haul Road Mine Infrastructure Area Open Channel Sediment Control Pond Road Railway Pipeline Contour Line (20 metre interval) Watercourse Waterbody Ì A 588000 No.1 Mine Chamberlain Seam Substation Sukunka Project Tenure Area Figure does not include mitigations related to waste rock stockpile placement required for protection of water quality 590000 592000 SUKUNKA COAL MINE PROJECT PREPARED BY: SUKUNKA PROJECT LAYOUT Project Development Area ROM Stockpile No.1 Mine Skeeter Seam 16 00 0110 19 00 Option D PREPARED FOR: WATER MANAGEMENT PLAN Data Sources: Glencore, Province of British Columbia, Government of Canada Disclaimer: Although there is no reason to believe that there are any errors associated with the data used to generate this product or in the product itself, users of these data are advised that errors in the data may be present. File Path: fig_10482_wmp_hydrology_03_03-01_sukunka_project_layout DATE: 25-JUN-15 FIGURE ID: 123110482 PROJECTION: UTM 10 DRAWN BY: DATUM: CHECKED BY: K. TERRY NAD 83 D. COOK FIGURE NO: 3.3-1 It should be noted that mitigations related to waste rock stockpile placement and water management identified in the water quality model report (Appendix 27.0-A.14 Water Quality Model) are not shown on Figure 3.3-1 or discussed in this document 6114000 < Transmission Line Options Option 1: Sukunka ! ! FSR to the Spectra Gas Compressor Station Option 2: Meikle Creek Road to ! ! Transmission Line at HWY 29 Option 3: Sukunka ! ! FSR to BC Hydro’s SKN Substation 6114000 6116000 14 00 6116000 A ! 6124000 ! ! ! 13 00 ! 00 12 A 12 00 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Environment Protection Measures June 28, 2015 The ditch loss for the proposed channels at the Sukunka Project is estimated to be less than 5 percent for the majority of channel conditions. The ditch loss for a given channel section is dependent on the hydraulic conductivity of the channel. Channel sections constructed in bedrock cut will exhibit relatively low ditch loss. Channels constructed in overburden or on fill materials will have greater losses. Areas where the in situ materials do not meet the required hydraulic conductivity criteria will be improved through installation of a liner, grouting or other ground improvement techniques. Figure 3.3-2, Figure 3.3-3 and Figure 3.3-4 illustrate typical channel sections constructed in rock cut, overburden and fill materials, respectively. The channels sections shown on Figure 3.3-3 and Figure 3.3-4 show the potential use of a liner to minimize ditch loss should it be necessary. The net seepage efficiency for the Project collection ditches is therefore estimated to be approximately 60 to 90 percent. The actual value will depend on the proportion of runoff contributing from areas with relatively high or low capture efficiency and ground conditions along the ditch alignment encountered during further investigation and construction. For the purposes of the water quality assessment, an overall net seepage efficiency of 85 percent was used (Appendix 27.0-A.14 Water Quality Model). 3.3.2.3 Sediment Control Ponds Sediment control ponds will be constructed downstream of most construction and all operations activities. The ponds will be designed in accordance with the Guidelines (BC MOE-LP 2001), and to the design criteria detailed in Section 3.3.3.1 below. General considerations are that the ponds be constructed with a long and narrow shape (5L:1W), with sufficient surface area to facilitate settling, and with sufficient depth to provide a minimum 1.5 m of water cover above accumulated sediment. The SCPs will be designed to settle sediment during 1 in 10 year flood events. Furthermore, the ponds will be designed with an overflow spillway sized to safely pass 1 in 200 year flood flows. Water treated in the SCPs will either be discharged to existing channels via energy dissipating structures (SSCP), or via water pipe to the Sukunka River (WSCP and NSCP). The locations of the three major proposed SCPs (SSCP, WSCP and NSCP) are shown on Figure 3.3-1. All sediment ponds will require inspection and maintenance on a scheduled basis, as well as after all substantial storm events (e.g., 24-hr rainfall exceeds 10 mm). 11 SUKUNKA COAL MINE PROJECT NORTH COLLECTION CHANNEL TYPICAL SECTION IN ROCK CUT ENVIRONMENTAL ASSESSMENT - DISCIPLINE Data Sources: Glencore, Province of British Columbia, Government of Canada Disclaimer: Although there is no reason to believe that there are any errors associated with the data used to generate this product or in the product itself, users of these data are advised that errors in the data may be present. File Path:Fig_3.3-2_rA - North Collection Channel Rock Cut DATE: 25-JUN-15 FIGURE ID: 123110482 DRAWN BY: PP PROJECTION: UTM 10 NAD 83 DATUM: CHECKED BY: DF PREPARED BY: PREPARED FOR: FIGURE NO: 3.3-2 SUKUNKA COAL MINE PROJECT NORTH COLLECTION CHANNEL TYPICAL SECTION IN OVERBURDEN ENVIRONMENTAL ASSESSMENT - DISCIPLINE Data Sources: Glencore, Province of British Columbia, Government of Canada Disclaimer: Although there is no reason to believe that there are any errors associated with the data used to generate this product or in the product itself, users of these data are advised that errors in the data may be present. File Path:Fig_3.3-3_rA - North Collection Channel Overburden DATE: 25-JUN-15 FIGURE ID: 123110482 DRAWN BY: PP PROJECTION: UTM 10 NAD 83 DATUM: CHECKED BY: DF PREPARED BY: PREPARED FOR: FIGURE NO: 3.3-3 SUKUNKA COAL MINE PROJECT NORTH COLLECTION CHANNEL TYPICAL SECTION ON FILL ENVIRONMENTAL ASSESSMENT - DISCIPLINE Data Sources: Glencore, Province of British Columbia, Government of Canada Disclaimer: Although there is no reason to believe that there are any errors associated with the data used to generate this product or in the product itself, users of these data are advised that errors in the data may be present. File Path:Fig_3.3-4_rA - North Collection Channel on Fill DATE: 25-JUN-15 FIGURE ID: 123110482 DRAWN BY: PP PROJECTION: UTM 10 NAD 83 DATUM: CHECKED BY: DF PREPARED BY: PREPARED FOR: FIGURE NO: 3.3-4 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Environment Protection Measures June 28, 2015 3.3.3 Water Management Design Elements For the purpose of the WMP, the Project has been subdivided into a number of hydrologic catchments delineated according to natural drainage boundaries and/or the artificial boundaries of collection and diversion ditches, as shown on Figure 3.3-1 and listed in Table 3.3-1. Table 3.3-1 Catchment Areas of Key Water Management Features Type Contact Water NonContact Water Description Catchment Area (km2) Area contributing to the north collection ditch and the north sediment control pond 9.64 Area contributing to the west collection ditch and the west sediment control pond 8.85 Area contributing to the south collection ditch and the south sediment control pond 2.01 Area contributing to the north diversion ditch and Skeeter Creek 3.62 Area contributing to the west diversion ditch and Chamberlain Creek 1.04 Area contributing to the south diversion ditch and Chamberlain Creek 8.49 3.3.3.1 Design Criteria A risk-based approach is used to select appropriate design storm events for each water management feature. This approach weighs the likelihood of failure versus the consequence of failure, on a case-specific basis. BMPs generally dictate minimum prescriptive standards; however, feature-specific design basis criteria may be used that exceed minimum standards should the calculated risk warrant it. Design storm events are developed by assessing the annual recurrence interval of precipitation events of a given magnitude, as described in Section 2.1.3. Design storm events are typically used as input parameters to a rainfall-runoff type storm water model such as HEC-HMS, HydroCAD, and TR-55. In northern climates such as in British Columbia, snowmelt is also considered to occur during the design storm event. The design criteria for various design elements are listed in the Table 3.3-2 below. 15 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Environment Protection Measures June 28, 2015 Table 3.3-2 Design Criteria Design Element Design Criteria Anticipated Exposure Time Diversion Ditches Peak flow from 1 in 10 year return period flood with a > 0.2 m freeboard Life of Mine Collection Ditches Peak flow from the 1 in 200 year return period flood with a > 0.2 m freeboard Life of Mine Sediment Control Ponds (surface area) 1 in 10 year return period flood hydrograph and a maximum settling velocity of 5 x 10-5 m/s Life of Mine Sediment Control Pond Spillways Peak flow from the 1 in 200 year return period flood hydrograph with a > 0.5 m freeboard Life of Mine Dewatering Open Pits 1 in 10 year return period 24-hour storm dewatered in 24 hours Life of Mine NOTES: PMP—Probable Maximum Precipitation PMF—Probable Maximum Flood 3.3.4 Water Management Measures by Project Phase This section describes the timing of specific water management elements that will be used where required throughout the site. The closure water management measures described in Table 3.3-3 include decommissioning much of the water management infrastructure and restoring natural drainage. These activities will only be completed once water quality is sufficient to allow discharge from the closed project site directly to Skeeter and Chamberlain creeks without resulting in unacceptable water quality within the receiving environment. 16 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Environment Protection Measures June 28, 2015 Table 3.3-3 Construction Water Management Measures Activity Potential Requirement Construct access roads Interrupt natural drainage Potable water needs Construct Construction Offices Clearing and grubbing open pit and waste rock stockpiles Septic and grey water production Sediment laden runoff Water Management Measures 1. Employ appropriate BMPs to route runoff and mitigate erosion 2. Potable water will be trucked to site 3. Construction office septic and grey water will be stored in tanks for offsite disposal in approved municipal waste water treatment systems 4. 5. 6. Construct diversion ditches above work area Construct collection ditches below work area Construct and route collection ditches to sediment control ponds Construct water discharge pipe and route water from North and West Sediment Control Ponds to the Sukunka River Employ appropriate BMPs 7. 8. Develop open pits Water requirement for coal washing and surface run-off management Construct CHPP Table 3.3-4 Dewatering 9. Prepare and commission dewatering system and route contact water to collection ditches 10. Construct Sukunka River water supply wells and pipeline 11. Build diversion ditches to divert uncontaminated run-off around the construction site. 12. Build construction collection ditches to divert surface run-off through a sediment control pond that will discharge to Skeeter Creek. After the North Collecting Ditch is constructed, the CHPP construction sediment pond will discharge into the North Collection Ditch. Operations Water Management Measures Activity Potential Effect/Need Water Management Measures 1. 2. Operate open pits and waste rock stockpiles Collect contact water Divert non-contact water Operate sediment control ponds Treat contact water 3. Maintain collection ditches Pump contact water from Pit 1 to CHPP to meet plant demand Pump remaining contact water from Pit 1 and all contact water from Pits 2 to 6 to nearest appropriate collection ditch 4. Maintain diversion ditches 5. Maintain sediment control ponds 17 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Monitoring Program June 28, 2015 Table 3.3-4 Operations Water Management Measures Activity Potential Effect/Need Water Management Measures 6. Operate CHPP Use contact water for coal wash when sufficient water is available. Use freshwater from the Sukunka River supply line to cover short fall Collect wash water, clarify, and then recirculate to the CHPP for re-use. Coal Wash 7. Operate Accommodation Camp Table 3.3-5 Potable water Septic and grey water 8. Maintain potable water supply wells 9. Maintain treatment system and discharge treated water into local watershed Closure Water Management Measures Activity Closure/Reclamation of Open Pits and Waste Rock Stockpiles = Potential Effect/Need Return natural drainage Water Management Measures 1. 2. Decommission dewatering systems and water supply systems Employ appropriate BMPs NOTES: More detailed information regarding closure is provided in the preliminary Reclamation Plan (Section 20.0-A.14) 4.0 Monitoring Program 4.1 MONITORING Effluent discharge from mining processes is currently regulated under the Environmental Management Act and effluent discharge permits issued by the BC MOE. Monitoring will be completed to confirm compliance with the permits issued. Water quality sampling and flow measuring facilities will be part of the design of the various water management measures to meet all monitoring requirements. Septic and grey water discharge is currently regulated by the BC MOE for discharges greater than 22.7 m3/d and by the BC Ministry of Health for discharges less than 22.7 m3/d. Monitoring will be completed to confirm compliance with any permits issued. Sampling and flow measuring facilities will be part of the design of the various water management measures to meet all monitoring requirements. Monitoring and reporting objectives are contained in Section 5.2 Water Quality. 18 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN Monitoring Program June 28, 2015 4.2 FOLLOW-UP AND ADAPTIVE WATER MANAGEMENT STRATEGY If effluent is found to be, or modelled to be, repeatedly outside of the guidelines, an adaptive management plan will be developed to ensure the effluent discharge conforms to permit requirements. An example of adaptive management is including provisions in the design of the SCPs for aiding settling (Section 4.2.1). If SCP effluent is not meeting guidelines for total suspended sediment (TSS), a settling aid will be considered. Further discussion on follow-up and adaptive water management is provided in Section 5.2 (Water Quality) of the Application. 4.2.1 Flocculants Use to Aid Settling The sedimentation ponds are being designed to meet the 15 mg/L TSS effluent criterion described in the Metal Mining Effluent Regulations and to settle particles 10 µm or greater during the 1 in 10-year, 24-hour runoff condition. The sedimentation ponds will be sized to promote gravity settling of sediment from the collection ditches within time frames appropriate to the sediment particle size. For example, sand and coarse silt settle within hours, while fine silt and clay will require 24 hours or longer to settle. During times of high flow, when TSS levels are high and there is insufficient time for natural settling to allow the TSS discharge criterion to be met, flocculants will be used to promote settling of sediment. Flocculants will be added to influent water upstream of the sedimentation ponds to allow time for settling. The kind and amount of flocculants to be used will be evaluated prior to operation, and a suitable dosing regimen developed. Considerations for selection and use of flocculants are (Clark and Jayasena 2013): • • Potential for toxicity to aquatic life in released effluent (resolved by selecting low-toxicity flocculants, typically a neutral, anionic or mixed neutral-cationic-anionic type, as higher toxicity is associated with cationic type flocculants; Clark 2010) Potential for reduced settling capacity, if the flocculants use is too high (a protective colloid effect, frequently irreversible, that results in decreased settling efficiency and increased TSS as more flocculants are added) The following information will be collected to guide use of flocculants (outlined in MELP 2001) • • • Review of available flocculants and selection of an effective, low toxicity flocculant Soil particle size analysis and settling tests on upslope soil samples to identify relevant size fractions of sediment and any needs for flocculants Sizing of the sedimentation pond to capture the plus 10 µm particle size when runoff flow into the pond is for the 10-year, 24-hour rainfall event The amount of flocculants required will take into account flow rate into the pond, TSS in water entering the pond, particle surface area, adequate mixing subsequent to adding the flocculants to the runoff (i.e., location of flocculants addition), and time needed for mixing in the flocculants. 19 PRELIMINARY MINE SITE WATER MANAGEMENT PLAN References June 28, 2015 When flocculants are used to settle sediment, toxicity of the sediment pond water will be tested using the Ceriodaphnia dubia bioassay (48 hour LC50) and rainbow trout bioassay (96 hour LC50). Because the flocculants bind to the sediment particles and settle in the ponds, minimal concentrations (and toxicity) of flocculants in pond discharge water are anticipated. The Environmental Management Act effluent permit will set the conditions for toxicity testing; however, it is anticipated that a sample will be collected for testing within 24 hours of starting flocculants use, and weekly thereafter. 5.0 References British Columbia Ministry Environment, Land and of Parks (MELP). 2001. Draft – Guidance for Assessing the Design, Size and Operation of Sedimentation Ponds used in Mining. Available online at: http://www2.gov.bc.ca/gov/DownloadAsset?assetId=8F1FAE8C9A D94A2CBFC5C570A41A2D0F. British Columbia Ministry of Environment. 2013. The Effluent Permitting Process under the Environmental Management Act – An Overview for Mine Project Applicants. Available online at: http://www.env.gov.bc.ca/epd/industrial/mining/pdf/effluent_permitting_ guidance_doc_mining_proponents_apr2013.pdf. Clark, J.P. 2010. Treatment of Mine Site Runoff Containing Suspended Solids Using Sedimentation Ponds – Optimizing Flocculant Addition to Ensure Discharge Compliance. In: Wolkersdorfer, C. and A. Freund (Editors), Mine Water and Innovative Thinking Proceedings of the 2010 International Mine Water Association. Sydney, NS. pp. 217-220 Clark, J.P. and H. Jayasena. 2013. Using the BC Guidance for Assessing the Design, Size and Operation of Sedimentation Ponds used in Mining to Comply with Federal/Provincial Sediment Control Legislation. Available at: http://www.academia.edu/6165975/ Clark_J_C_et_al_BC_Mine_2013. Demarchi, D. 2011. The British Columbia Ecoregion Classification – Third Edition. Ministry of Environment. Victoria, BC. Available online at: http://www.env.gov.bc.ca/ ecology/ecoregions. Herschfield, D.M., 1961. Rainfall Frequency Atlas of the United States for Durations from 30 Minutes to 24 Hours and Return Periods from I to 100 Years. U.S. Department of Commerce, Technical Paper No. 40. Herschfield, D.M., 1965. Method for estimating probable maximum precipitation, J. American Waterworks Association, Vol. S7, p. 965-972. Knight Piesold Ltd. 2014a. Watershed Model Report. Ref. No. VA101-511/1-2, Rev. 0, In Progress. Knight Piesold Ltd. 2014b. Baseline Hydrology Report. Ref. No. VA101-511/1-1, Rev. 0, January 30 2014. 20