CONSTRUCTION ENVIRONMENTAL MANAGEMENT PLAN FOR THE JAY DIKE AND NORTH DIKE. Dominion Diamond Ekati Corporation

Transcription

1 CONSTRUCTION ENVIRONMENTAL MANAGEMENT PLAN FOR THE JAY DIKE AND NORTH DIKE Prepared for: Prepared by: Dominion Diamond Ekati Corporation Golder Associates Ltd.

2 Table of Contents Table of Contents 1 INTRODUCTION Project Overview Scope and Purpose Best Applicable Practices BACKGROUND Physical Setting Climate Lake Currents Investigation Programs Lakebed Stratigraphy Sediment Settling Constraints CONSTRUCTION SCOPE AND SCHEDULE CONSTRUCTION PHASE ORGANIZATION AND RESPONSIBILITIES Overall Project Organization Responsibilities Owner s Responsibilities Engineer s Responsibilities Contractor s Responsibilities MATERIALS FOR EARTHWORKS Overview Rockfill Crushed Waste Rock Till Environmental Considerations Management and Controls Monitoring Contingencies DIKE ROADS AND LAYDOWNS Dike Roads Laydowns Environmental Considerations Management and Controls i

3 Table of Contents 6.5 Monitoring Contingencies TURBIDITY BARRIER Design Deployment and Removal Environmental Considerations Controls Monitoring Contingencies JAY DIKE FILL PLACEMENT, EXCAVATION, AND FOUNDATION PREPARATION Overview Construction Method Rockfill Placement Excavation Fine and Coarse Filter Placement Environmental Considerations Management and Controls Monitoring Contingencies CUT-OFF WALL Overview Construction Method Environmental Considerations Management and Controls Monitoring Contingencies JET GROUTING Overview Construction Method Environmental Considerations Management and Controls Monitoring Contingencies CURTAIN GROUTING Overview ii

4 Table of Contents 11.2 Construction Method Environmental Considerations Management and Controls Monitoring Contingencies INSTRUMENTATION Instrumentation System Installation Environmental Considerations Management and Controls Monitoring Contingencies NORTH DIKE Construction Method Environmental Considerations Management and Controls Monitoring Contingencies SUB-BASIN B DIVERSION CHANNEL Overview Construction Method Environmental Considerations Management and Controls Monitoring Contingencies REFERENCES Maps Map Location Plan Map General Arrangement Plan Map Year 1 Summer Construction Turbidity Barrier Layout Map Year 2 Summer Construction Turbidity Barrier Layout Map Year 3 Summer Construction Turbidity Monitoring Locations Map Preliminary Jet Grouting Area Map Sub-Basin B Diversion Channel Catchment Map Sub-Basin B Diversion Channel Plan View iii

5 Table of Contents Figures Figure Turbidity and Total Suspended Solids Trends in 2015 Column Test Figure 3-1 Jay Dike Construction Schedule Figure Typical Turbidity Barrier Profile Figure Typical Dike Construction Section Figure Jay Dike Low Permeability Element Typical Cross-Sections Figure Continuous CSB Cut-off Wall Construction Method Figure Typical North Dike Construction Section Photos Photo Test Column with Composite Sediment Sample Introduced at Surface Photo Typical Cut-Off Wall Excavation Using Slurry Trench Technology Photo Typical Batching Plant Tables Table 3-1 Jay Dike and North Dike Construction Scope and Schedule Summary Table Fine Filter Particle Size Distribution Table Coarse Filter (200 mm minus) Particle Size Distribution Appendices Appendix A Appendix B Jay Dike Construction Suspended Sediment Monitoring and Management Plan QA/QC Manual iv

6 Abbreviations and Units of Measure Abbreviations Abbreviation BAP CEMP CPT CRMP CSB Dominion Diamond Ekati mine FPK Golder LiDAR non-pag NWT OMS PVC QA QC TSS WEMP WROMP WRSA Definition Best Applicable Practices cone penetration tests Caribou Road Mitigation Plan cement-soil-bentonite Dominion Diamond Ekati Corporation Ekati Diamond Mine fine processed kimberlite Golder Associates Ltd. light detection and ranging non-potentially acid generating Northwest Territories Operation, Monitoring, and Surveillance polyvinyl chloride Quality Assurance Quality Control total suspended solids Wildlife Effects Monitoring Plan Waste Rock and Ore Storage Management Plan Waste Rock Storage Area Units of Measure Unit Definition % percent C degrees Celsius cm/s centimetres per second g/m 2 grams per square metre khz kilohertz km kilometres km/h kilometres per hour km 2 square kilometres kpa kilopascals masl metres above sea level m metres m 3 m/s mm cubic metres metre per second millimetres v

7 Abbreviations and Units of Measure Unit mm/year ohm Definition millimetres per year unit of resistance vi

8 Section 1, Introduction 1 INTRODUCTION 1.1 Project Overview Dominion Diamond Ekati Corporation (Dominion Diamond) is proposing to develop the Jay pipe as part of its existing Ekati Diamond Mine (Ekati mine), located approximately 300 kilometres (km) northeast of Yellowknife in the Northwest Territories (NWT). The Jay pipe is located beneath Lac du Sauvage, in the southeastern portion of the Ekati claim block, approximately 25 km from the main facilities and approximately 7 km to the northeast of the Misery Pit (Map 1.1-1). Most of the facilities required to support the development of the Jay pipe and to process the kimberlite currently exist at the Ekati mine. The new facilities that will be developed to support mining of the Jay pipe will include two water-retaining dikes (the Jay Dike and North Dike), an open pit, roads, a power line, pumping and pipeline systems, ore transfer pads, a waste rock storage area (WRSA), and a diversion channel. The general arrangement of the is shown in Map The Jay pipe is located approximately 1.2 km from the western shoreline of Lac du Sauvage covered by approximately 35 metres (m) of water. The pipe will be isolated from the remaining portion of Lac du Sauvage by the construction of two water retaining dikes. The Jay Dike will be constructed around the perimeter of the Jay Pit and will connect to the shoreline in the south and a small island in the north. Between the shoreline and this small island is a low-lying marshy area and small channel that could be a persistent source of seepage into the dewatered area. The North Dike will be constructed across this channel to reduce potential inflows into the dewatered area and open pit. The dikes will allow the isolated portion of Lac du Sauvage to be dewatered. Once dewatered, open pit mining can occur. The area will be maintained in a dewatered state throughout the life of the Jay mining operations, until back-flooding commences as part of closure. Kimberlite from the Jay Pit will be transported to the existing processing facilities at the Ekati main camp, along the new Jay Road and the existing Misery Road. Before processing, the kimberlite may be stored within temporary kimberlite storage areas. At the processing plant, the diamonds will be physically separated from the kimberlite, leaving coarse processed kimberlite and fine processed kimberlite (FPK) behind. The fine and coarse processed kimberlite will be stored in the mined-out Panda and Koala pits. 1-1

9 ³ Sable EKATI MINE FOOTPRINT DIAVIK MINE FOOTPRINT PROPOSED JAY FOOTPRINT PROPOSED SABLE FOOTPRINT KIMBERLITE PIPE SABLE ALL-SEASON ROAD WINTER ROAD Ursula Lake Exeter Lake LEGEND TIBBITT TO CONTWOYTO WINTER ROAD NORTHERN PORTION OF TIBBITT TO CONTWOYTO WINTER ROAD ELEVATION CONTOUR (10 m INTERVAL) WATERCOURSE Jay Kimberlite Pipe Lac du Sauvage Existing Misery Road Lake D3 (Counts Lake) Duchess Lake Fox Operation Paul Lake - Fox Pit Airstrip Koala Pit North-Koala Pit Main Camp Grizzly Lake Long Lake Containment Facility Ekati Mine Panda Pit Beartooth Pit WATERBODY Pigeon Pipe Misery -----Operation CANVEC NATURAL RESOURCES CANADA, 2012 NATURAL RESOURCES CANADA, CENTRE FOR TOPOGRAPHIC INFORMATION, 2012 DATUM: NAD83 PROJECTION: UTM ZONE 12N Misery Pit Hammer Lake REFERENCE Lynx SCALE 1:175,000 - Lac de Gras PROJECT TITLE KILOMETRES JAY PROJECT NORTHWEST TERRITORIES, CANADA JAY PROJECT LOCATION PLAN PROJECT A.80 DESIGN GIS Lac de Gras Diavik Mine G:\CLIENTS\DOMINION\DDEC Jay and Lynx Projects\Figures\ _Jay_Stage_4\2090_Permitting_Licensing\10_Engineering_Support\CEMP\Map1_1-1_JayProjectLocation.mxd ESKER CHECK REVIEW CW 17/03/16 DA 31/05/16 ANK JC 31/05/16 31/05/16 FILE No. SCALE AS SHOWN REV MAP

10 Initial Dewatering Pum ping System 1 Approximate Approximate Storage Storage Area Area for for Competent Competent Overburden Overburden Soils Soils Laydown Area 5 Jay Dike Generator Jay Waste Rock Storage Area North Dike Approximate Lakebed Sediment Storage Area Potential Quarry ³ Lac du Sauvage LEGEND EKATI MINE FOOTPRINT (MISERY OPERATION) NORTHERN PORTION OF TIBBITT TO CONTWOYTO WINTER ROAD BATHYMETRY CONTOUR (5 m INTERVAL) ELEVATION CONTOUR (5 m INTERVAL) WATERCOURSE WATERBODY JAY PROJECT FOOTPRINT JAY TO MISERY PIPELINE APPROXIMATE JAY PIT CREST LAYDOWN AREA PROPOSED JAY PROJECT INFRASTR UCTURE PROPOSED JAY ROAD Laydown Area 4 PUMPING SYSTEM AREA Laydown Area 1 LYNX PROJECT FOOTPRIN T MISERY TO LYNX PIPELINE LYNX PROJECT INFRASTRUCTURE Proposed Jay Magazine Generator Initial Dewatering Pum ping System 2 Laydown Area 2 Jay Substation rt h in d ist Laydown Area 3 g Mi se ry Ro Jay Ro a Ex ad Ro ad Lake Ac36 Lake Ac35 Crusher and Stockpile Area Esker Cut Stockpile Existing Magazine 1. DESIGNS ARE C URRENTLY A WORK IN PROGRESS REFERENCES 1. JAY PROJECT DETAILED D ESIGN DIKE IFT DRAWING NO ISSUED FOR TENDER ON JANUARY 15, JAY PROJECT DETAILED D ESIGN CHANN EL IFT DRAWING NO ISSUED FOR TENDER ON JANUARY 15, JAY PROJECT WASTE ROCK STORAGE AR EA DESIGN REPORT DRAWING NO , DATED FEBRUARY 18, LIDAR AND BATHYMETRIC DATA OBTAINED FROM AURORA, WATER OBTAINED FROM CANVEC NATURAL RESOURCES CANADA, 2012 DATUM: NAD83 PROJECTION : U TM ZON E 12N 500 Pip eli Misery Camp and Truck Shop ad Lynx Waste Rock and Overburden Stockpile Area Misery Waste Rock Storage Area NOTES n e Ro PROJECT SCALE 1:30, G:\CLIENTS\DOMINION\DDEC Jay and Lynx Projects\Figures\ _Jay_Stage_4\2090_Permitting_Licensing\10_Engineering_Support\CEMP\Map1_1-2_JayProjectGeneralArrangement.mxd No Sub-Basin B Diversion Channel Lake B1 (Christine Lake) Misery Pit TITLE METRES JAY PROJECT NORTHWEST TERRITORIES, CANADA JAY PROJECT GENERAL ARRANGEMENT PLAN PROJECT Existing Winter Road DESIGN Lac de Gras CW /03/16 GIS AK/LS REVIEW DA 06/06/16 JC 06/06/16 CHECK 06/06/16 FILE No. SCALE AS SHOWN REV MAP A

11 Section 1, Introduction 1.2 Scope and Purpose This document describes the (CEMP) to be implemented to minimize environmental effects from the construction of the Jay Dike, North Dike, and other associated infrastructure. The plan describes each of the on-land and in-lake activities required to construct the Jay Dike and North Dike including the sourcing of materials, and their placement to form the dike. For each construction activity, the CEMP outlines the environmental monitoring and controls planned to address environmental risks. Where appropriate, the CEMP also details contingency measures that can be implemented, should conditions change. The CEMP does not include dewatering of the diked area of Lac du Sauvage. Consistent with the existing Ekati mine Water Licence, a Dewatering Plan will be prepared and submitted to the Wek'èezhıì Land and Water Board for approval prior to the commencement of dewatering (i.e., following approximately three years of dike construction activities). The Dewatering Plan will include details on schedule, locations, volumes, mitigation, and monitoring. 1.3 Best Applicable Practices Dominion Diamond is committed to implementing Best Applicable Practices (BAP) in construction of the. BAP comprises the selection of construction methods and management controls that will be used to minimize, to the extent practical, the environmental impact of the construction activities. BAP encompasses the following principles: use proven technology; consider the recommendations of qualified experts; have limited impact on schedule; and, be practical given the site conditions. Monitoring methods must facilitate the implementation of BAP and enable timely responses to incidents. 1-1

12 Section 2, Background 2 BACKGROUND 2.1 Physical Setting Located in the Canadian sub-arctic, the general physical setting of the is typical of a remote northern environment. Cold winter conditions dominate the site, with only approximately four months of spring/summer/fall where daily temperatures are above freezing. Winters are long, and daily temperatures often fall below -30 degrees Celsius ( C) during winter months. The is located in the Lac du Sauvage basin, which has a drainage area of 1,461 square kilometres (km 2 ) and is the largest single tributary to Lac de Gras. The Lac de Gras drainage basin is located at the headwaters of the Coppermine River, which flows north into the Arctic Ocean at the hamlet of Kugluktuk. The topography across the site is generally flat with local surface reliefs rising up only 20 m. Elevation ranges from approximately 416 to 465 metres above sea level (masl). The local terrain is characterized by boulder fields, tundra, esker, and lakes/wetlands. The terrestrial vegetation is composed of species adapted to freezing temperatures, low nutrient levels, and localized areas of drought and standing water. 2.2 Climate The site is located in a region of the NWT that experiences a sub-arctic climate characterized by long, dark, very cold winters and short, cool to mild summers accompanied by long daylight hours, with a mean annual air temperature of -9.6 C (Dominion Diamond 2014, Annex X). Seasonal mean air temperatures remain below zero for three of the four seasons, from fall through to spring. Seasonal air temperatures are lowest in the winter, when the mean air temperature is -28 C, and are highest in the summer, when the mean air temperature is 10 C. The annual average precipitation at the site is 344 millimetres per year (mm/year) and falls almost equally as snow and rainfall. Average annual evaporation for small waterbodies in the area is estimated to be 272 millimetres (mm) between June and September. The average annual loss of snowpack to sublimation and snow redistribution is estimated be 30 percent (%) of the total precipitation for the winter period, between October and May. The is located within a region of continuous permafrost. In this region, the layer of permanently frozen subsoil and rock is generally deep and overlain by an active layer that thaws during summer. The depth of the active layer in the Misery Pit area ranges from approximately 1.0 to 2.7 m. The depth of the active layer in the area (on-land facilities) is expected to be similar to that measured near the Misery Pit area. Based on available thermistor data collection and interpretation, the permafrost conditions at the site indicate a depth of permafrost that is estimated to be 320 to 485 m at locations that are not affected by waterbodies (Dominion Diamond 2014, Annex IV). Unfrozen zones (talik zones) occur beneath waterbodies, and permafrost is expected to be absent below the majority of Lac du Sauvage (Dominion Diamond 2014, Annex IV). Permafrost usually exists under the lake shoreline where the depth of water is less than 1 m and winter lake ice freezes to the lake bottom. Although permafrost occurs under islands and adjacent to waterbodies, the permafrost depth is expected to be less than the depth under land located away from waterbodies. It will vary below the islands and peninsulas in Lac du Sauvage depending on their sizes. 2-1

13 Section 2, Background 2.3 Lake Currents Modelling has been conducted to predict the lake currents in Lac du Sauvage in the vicinity of where the dikes will be constructed, during the open water season (i.e., when ice does not exist on the lake). The modelling took into account wind speed and direction, changes in atmospheric pressure, changes in density gradients, and tributary and non-tributary inflows to the lake. The modelling also considered how the different phases of the dike development might influence lake currents. The model was run using wind speed data collected from the nearby Diavik Diamond Mine in the period from July 2009 to December The model demonstrated that the currents in the lake are largely wind induced and vary according to wind direction. The model predicted that the most frequent current speed in Lac du Sauvage during the open-water season (July to October) is between 0 and 6 centimetres per second (cm/s). The maximum modelled lake current generated by storm events, using the 5 years of data, was 40 cm/s which corresponded to a storm with an average wind speed of 54 kilometres per hour (km/h) from the NNW over an approximately 8 hour period. Additional modelling was conducted to assess potential currents associated with wind storms of various intensities and durations. For an extreme wind storm, with a wind speed of 110 km/h over a one hour period, the maximum modelled current speed was approximately 93 cm/s. 2.4 Investigation Programs Geotechnical and hydrogeological field investigation programs were carried out in 2014 and 2015 between the months of February and April to obtain information to evaluate the conditions in the area of the Jay Pit and beneath the proposed dike alignments. Data were collected on soil and bedrock conditions, thermal characterization, and hydrogeological properties. A combination of in situ and laboratory testing was also carried out. Data obtained from the investigation programs are presented in the respective factual reports (Golder 2014a,b, 2015a,b, 2016). Each program is summarized below. Winter 2014 Investigation A total of 26 sonic and 22 diamond boreholes were drilled along the proposed dike alignments identified in the conceptual design report (Golder 2014a) and the Jay-Cardinal Project conceptual design report (Golder 2014c). Eight boreholes were drilled on land and 40 from the frozen surface of Lac du Sauvage. Seven sonic and six diamond boreholes were drilled along the pre-feasibility Jay Dike alignment. Seven thermistors were installed: two located along the dike alignment and five located several kilometres to the northwest and to the southeast of the dike alignment. Winter 2015 Investigation A total of 67 sonic, 19 diamond, and 111 rotary-percussive (air track) boreholes were drilled along the pre-feasibility Jay Dike alignment, as well as several alternative dike alignments. A total of 15 boreholes were drilled on land and the remainder from the frozen surface of Lac du Sauvage. 2-2

14 Section 2, Background Cone penetration testing (CPT) and shear vane testing was carried out at 19 and 13 borehole locations, respectively, paired with sonic drilled boreholes. Four thermistors were installed along the dike alignment. In situ hydrogeological testing of the soil, soil/bedrock contact, and shallow bedrock was carried out concurrently as part of each field investigation program. Depending on the method of drilling and conditions encountered, the testing was carried out as a combination of slug injection, slug withdrawal, and constant rate injection using either temporary standpipe piezometers or pneumatic packers. Thermistor cables were installed in select boreholes on the abutments and islands along the Jay Dike alignment. The thermistors were installed to record ground temperatures with depth and over time. In June and July of 2013, Aurora Geosciences Ltd. conducted a bathymetric survey of Lac du Sauvage to provide information on the depth of water (Aurora 2013). The bathymetric survey was completed at a 50 m line spacing with a sonar frequency of 200 kilohertz (khz). In August 2013, Aurora subcontracted LiDAR Services International Inc. to conduct an airborne light detection and ranging (LiDAR) survey that covered the area. LiDAR surveys are able to detect subtle topographic features and measure the land surface elevation beneath the vegetation canopy, and are able to resolve spatial derivatives of elevation. The data collected form the bathymetric and LiDAR surveys were used to provide water depths, lakebed surface elevations, and topographic elevations in the vicinity of the Jay Dike and North Dike. During the summers of 2014 and 2015, Golder Associates Ltd. (Golder) carried out sub-bottom profiling in the vicinity of the Jay Dike and North Dike to try and assess the contact between lakebed sediments, competent soil, and bedrock (Golder 2014d, 2015c). During the summer of 2014, Golder also conducted a sidescan sonar survey to identify the presence of boulders. In 2015, a GoPro Hero4 camera was used to image boulder distribution and lakebed conditions with photos taken approximately every 1.5 m along the pre-feasibility and alternative dike alignment segments. A single beam bathymetry survey was collected concurrently, such that each photo had a corresponding depth and location. Data collected from surveying were interpreted to provide the approximate depths to each stratigraphic contact. Borehole data were utilized for calibration and to aid with interpretation. The interpreted contact surfaces have been used in the detailed design. 2.5 Lakebed Stratigraphy Boreholes drilled as part of the winter 2014 and 2015 investigation programs, as described in Section 2.4, were reviewed to assess the variability in ground conditions anticipated during dike construction in the general vicinity of the dike. Data from the boreholes within the Jay pipe area were utilized, but data from drill hole locations further beyond the Jay pipe were not utilized (i.e., Conceptual Dike Design Study Option 1 and Jay-Cardinal Conceptual dike design alignments, [Golder 2014b,c]). Three main stratigraphic units were identified from the investigation programs as follows: lakebed sediment, consisting of: 2-3

15 Section 2, Background upper/soft lakebed sediment; and, lower/consolidated sediment. competent soil; and, bedrock. In addition, along portions of the dike alignment, a surficial layer of boulders and cobbles is present. At these locations, limited to no lakebed sediments are present. In general, this layer of boulders and cobbles is found in shallower water, along the shoreline or near islands. A single area of clustered boulders and cobbles in deeper water, approximately 9.5 m, was noted during the 2015 geophysical survey (Golder 2015c), and other sporadic boulders and cobbles were observed on the lakebed surface. Lakebed sediments are generally described as very soft to stiff, non-cohesive to slightly cohesive, silty clay to clayey silt, with trace to no fine-grained sand. Results from CPT indicate that two different zones are present: an upper lakebed sediment unit which is soft to very soft, and a lower consolidated, firm to stiff unit. The combined thickness of lakebed sediments (soft and consolidated units) recorded in boreholes drilled in the general vicinity of the Jay Dike varied from 0 to 5.8 m, with an average thickness of 2.4 m. The upper lakebed sediment thickness ranged 0 to 2.1 m, with an average of 1.2 m, while the consolidated sediment unit ranged 0 to 1.7 m, with an average thickness of 1.2 m. In general, lakebed sediment thickness was found to be greater in the troughs and deeper water areas than in shallower areas. 2.6 Sediment Settling Four column settling tests were conducted on samples of the lakebed sediment obtained from near the proposed Jay Dike location during the 2014 geotechnical investigation. These tests were later supplemented by column tests carried out on a composite sample of five sediment samples taken from the Jay Dike area during the 2015 investigation. The tests were carried out in lake water collected from Lac du Sauvage. Sediments were first suspended in the lake water and then left to settle naturally by gravity. During this period, measurements of particle size distribution, total suspended solids (TSS), and turbidity were taken from the water column. A Photo of the 2015 column test is provided in Photo Turbidity and TSS measurements from the water column of this same test are shown in Figure The settling tests indicate that both the TSS and turbidity of the water in the column decreased rapidly following suspension. For example, in the test shown in Figure 2.6-1, turbidity decreased by more than 60% in the first two hours and more than 90% over the first four days. The results of the column testing were used to inform the design of the turbidity management measures for the Project. 2-4

16 Section 2, Background Photo Test Column with Composite Sediment Sample Introduced at Surface 2-5

17 Section 2, Background Figure Turbidity and Total Suspended Solids Trends in 2015 Column Test NTU = nephelometric turbidity units; TSS = total suspended solids; mg/l = milligrams per litre. 2.7 Constraints The Jay Dike and North Dike have been designed to minimize environment impacts within the context of the physical, schedule, climatic, and project constraints. Key constraints on the dikes include: a short summer construction season; the lakebed bathymetry; soft and variable depth lakebed sediments; the need to use large-scale construction equipment; areas of cultural and environmental significance; caribou migration routes; and, limited land areas along the dike alignment. 2-6

18 Section 2, Background Cognizant of these constraints, Dominion Diamond has applied BAP to each aspect of the design and construction strategy for the. Examples of where BAP has been applied, include: use of existing Ekati mine infrastructure where possible; seasonal staging and scheduling of construction activities to take advantage of winter months and reduce overall construction time; the use of waste rock materials from existing pits to supply construction materials for the dikes and roads, to the extent possible, and reduce additional land disturbance; development of the Mine Water Management Plan, which includes diversion of water around the dike, into the lake through construction of the Sub-Basin B Diversion Channel; the development of a turbidity management system for dike construction, including the use of turbidity barriers to manage the area exposed to elevated levels of suspended solids generated during construction and that considers published experience from similar projects in northern Canada; implementation of erosion and sediment controls (e.g., during construction of the Sub-Basin B Diversion Channel); creation of laydown areas at multiple locations to reduce vehicle travel distances during construction; and, working with a team of experienced environmental, construction and engineering specialists through design and extending into construction and operations. 2-7

19 Section 3, Construction Scope and Schedule 3 CONSTRUCTION SCOPE AND SCHEDULE The Jay Dike construction is anticipated to start with the mobilization of equipment on the winter road in the winter prior to the first year of dike construction. Construction of the Jay Dike and North Dike will be completed in approximately three years, allowing dewatering of the isolated area to commence once the dike is completed. A summary of the scope and schedule for construction of the Jay Dike and North Dike is provided in Table 3-1. The approximate schedule is illustrated in Figure 3-1. The schedule in Figure 3-1 includes the early works (road construction and aggregate) that will be necessary to allow commencement of the Jay Dike earthworks. Table 3-1 Jay Dike and North Dike Construction Scope and Schedule Summary Year Construction Year 1 Construction Year 2 Construction Year 3 Construction / Operations (Year 0) Activities Mobilization Crushing Turbidity barrier Laydown Road to water s edge Jay Dike winter rockfill placement Crushing Turbidity barrier Laydown Jay Dike earthworks Crushing Turbidity barrier Jay Dike earthworks Jay Dike Curtain grouting Jay Dike Jet grouting Jay Dike Curtain grouting Jay Dike Jet grouting Jay Dike Instrumentation Demobilization Jay Dike earthworks Jay Dike winter rockfill placement North Dike Jay Dike Curtain grouting Jay Dike and North Dike Instrumentation Pipeline installation Jay Dike Jet grouting Diversion channel 3-1

20 Section 3, Construction Scope and Schedule Figure 3-1 Jay Dike Construction Schedule 3-2

21 Section 4, Construction Phase Organization and Responsibilities 4 CONSTRUCTION PHASE ORGANIZATION AND RESPONSIBILITIES 4.1 Overall Project Organization Construction of the will be executed by Dominion Diamond, working with a team of environmental, construction and engineering specialists, as appropriate. The project team will comprise of the parties listed below. Owner. As the Owner, Dominion Diamond, provides overall control and coordination of the site. Dominion Diamond will also provide many of the materials required for the construction works. To achieve this, the Owner s team will include a Project Manager, Environmental Manager, Health and Safety Manager and a project support team. Engineer. Golder is the engineer of record and will work with Dominion Diamond to oversee implementation of the technical requirements of the Project. The Engineer will be present on site during construction to carry out Quality Assurance (QA) and check that the constructed works satisfy the design. Contractor. Contractor(s) will be retained by Dominion Diamond to execute the construction. The Contractor(s) and any subcontractors will be responsible for mobilizing the required manpower, equipment, and materials not provided by the Owner to successfully execute the work described in the contract documents. The work will require close cooperation between the Owner, Engineer, and Contractor. All three parties will interact daily during dike construction to confirm that standards are met regarding safety, environment, technical and contractual aspects of the work. Meetings will be held to discuss progress and plan the construction activities. 4.2 Responsibilities Owner s Responsibilities The Owner is responsible for: health and safety at the work site and the mine site; obtaining all relevant permits; maintaining compliance with all Federal and NWT legislated requirements; preparation of all regulatory documents; procurement, including administering the tender and bid evaluation process for hiring the Contractor; engaging the Engineer; assembling and engaging an independent Jay Dike Geotechnical Review Board; 4-1

22 Section 4, Construction Phase Organization and Responsibilities providing and restricting access to the site as required for the Engineer and Contractor to complete their tasks; providing rockfill, crushed aggregates, till, cement, bentonite, and diesel required to complete the work; identification of water sources, disposal areas for waste materials, and stockpile areas; controlling and monitoring the cost and schedule for the Project; supervision and management of the Contractor; contract management and administration, including performance guarantees and insurances; assessment and approval of claims for payment; and, overall environmental management, including communication of primary standards and requirements to the Engineer and the Contractor Engineer s Responsibilities The Engineer is responsible for: the design, including the Drawings and Specifications stamped by an appropriately qualified Professional Engineer registered to practice in the NWT; permitting support; design of environmental mitigation measures, as requested by the Owner (i.e., turbidity management/curtains); design modifications and clarifications that may occur before and/or during construction; reviewing Quality Control (QC) documentation submitted by the Contractor; preparation of a QA plan for the work; QA of the work, including observing, testing, inspecting, documenting, monitoring, and reporting the relevant construction activities; implementing changes to the frequency of QA testing and monitoring, as necessary; stopping work that is not in accordance with the design; specialist technical support and advice, as required for the duration of the construction work; support to the Owner in presentation to the Jay Dike Geotechnical Review Board; preparation of an as-built report stamped by an appropriately qualified Professional Engineer registered to practice in the NWT for submission to the Owner at the completion of the work; and, input to the Operation, Monitoring, and Surveillance (OMS) manual for the completed works. 4-2

23 Section 4, Construction Phase Organization and Responsibilities Contractor s Responsibilities The Contractor is responsible for: health and safety of the Contractor s and any subcontractor s employees; planning, sequencing, and executing the work in accordance with the design and required environmental standards; supply of all materials, labour, supervision and equipment, except those supplied by Owner, required to complete the work; supervision, coordination, and administration of subcontractors, if required; QC of the works, including checking the work as it progresses, testing, inspecting, documenting, monitoring, and reporting the construction activities; and, survey and survey control for layout, QC, and as-built survey of the work. 4-3

24 Section 5, Materials for Earthworks 5 MATERIALS FOR EARTHWORKS 5.1 Overview Both the Jay Dike and North Dike include: rockfill; crushed granular fine and coarse filters; and, a composite low-permeability element. For the Jay Dike, the low-permeability element will include a cement-soil-bentonite (CSB) cut-off wall, supplemented by jet grouted columns where the cut-off wall does not extend to bedrock, and curtain grouting of the bedrock. For the North Dike, low-permeability element includes a bituminous geomembrane liner and bentonite-treated fine filter layer. 5.2 Rockfill Rockfill for construction of the dike will be non-potentially acid generating (non-pag) granite primarily sourced from the Lynx Pit waste rock. The rockfill will be stockpiled in the Lynx WRSA before use, as required to supply the construction schedule for the dike. Waste rock from Lynx Pit may be hauled directly to the area for use. The use of waste rock from the Lynx Pit has the environmental benefit of reducing the ultimate size of the WRSAs for the Ekati mine. A portion of the rockfill required for construction may also be sourced from a quarry, developed within the ultimate footprint of the Jay WRSA. The decision to develop the quarry will depend on the quantity of material required for construction and the amount of waste material produced from mining of the Lynx Pit. Rockfill sourced from the potential quarry location will have a shorter haulage distance to the Jay Dike. If developed, the quarry would be backfilled with overburden and waste rock mined from the Jay Pit during operations. The rockfill sourced from both locations will be granite and will be non-pag. Material selected for the construction will have a maximum particle diameter of approximately 1.0 m, and will contain less than 5% silt (mass of particles passing mm). The rockfill will also be free of clay, organic matter, debris, and other deleterious materials. 5.3 Crushed Waste Rock Non-PAG waste rock from Lynx Pit will be crushed to produce: fine filter, coarse filter (200 mm minus), and 56 mm minus materials for construction of the roads, laydown areas, and fine and coarse filter zones within the dikes. Each material will be crushed to meet the engineering requirements using a dedicated crusher located adjacent to the Lynx WRSA. Crushed materials will be stockpiled adjacent to the crusher, or in other designated stockpiles, for use in construction. The particle size distributions for the fine filter, and coarse filter (200 mm minus) materials are provided in Tables and

25 Section 5, Materials for Earthworks Table Fine Filter Particle Size Distribution Particle Size (mm) mm = millimetres; % = percent. Percent Passing (% by mass) Table Coarse Filter (200 mm minus) Particle Size Distribution Particle Size (mm) mm = millimetres; % = percent. Percent Passing (% by mass) The crusher will include the following principal components: 1) Vibratory feeder with scalping bars spaced at 185 mm; 2) Jaw Crusher; 3) Cone Crusher; 4) Screen; and, 5) Parallel Twin Cone Crushers. 5-2

26 Section 5, Materials for Earthworks The crusher components and set-up may be adjusted, as required to achieve the material specifications using the available rock. The crusher will not be enclosed and will operate 24-hours per day. Operation will be limited to approximately five months per year, nominally from May to September, depending on weather conditions, crusher productivity, and material requirements. 5.4 Till Till will be used in the production of the CSB cut-off wall. The till will be sourced from pre-stripping of the Lynx Pit. Till will be stored in a designated stockpile within the Lynx WRSA in preparation for construction of the Jay Dike. The till used in construction will be free of deleterious materials, debris, and particles greater than approximately 100 mm. This specification will be achieved by a combination of selective material use, spreading and reworking and screening materials, as required. 5.5 Environmental Considerations The main environmental risks associated with the preparation of the earthworks materials are: dust from crushing, screening, or loading facilities; release of sediment in runoff water from stockpiles; and, use of potentially acid generating materials. 5.6 Management and Controls The control measures outlined below will be implemented in the supply of earthworks materials for construction. Materials stockpiled within WRSAs will be managed in accordance with the Ekati mine Waste Rock and Ore Storage Management Plan (WROMP). Erosion and sediment control measures currently in place at the Ekati mine will be used to manage sediment from stockpiles. Stockpiles of different materials will be built far enough apart to prevent intermingling. The crushing and screening plant will be maintained in good working condition. The crushing and screening units will be outfitted with dust suppression guards to control airborne dust. All of the earthworks materials used in construction will be free of organic matter, debris, and other deleterious materials. 5-3

27 Section 5, Materials for Earthworks Geochemical characterization of the main rock types at the Ekati mine has been ongoing since 1995 (refer to the Ekati mine WROMP and Annex VIII of the Developer s Assessment Report). There is a detailed understanding of the geochemistry of the various rock types present at the Ekati mine. The granitic rock and till at the Ekati mine has been characterized through geochemical testing to be non-pag. Only granitic rock and till will be used in construction of the Jay Dike, North Dike, roads, and laydowns. 5.7 Monitoring The earthworks materials used for construction of the Jay Dike will be monitored during production and construction. This will include a combination of regular visual inspections and QC/QA testing of the physical properties. QC/QA testing will be carried out on the fine filter and coarse filter material as it is produced, in the stockpiles, and as it is placed, to demonstrate that these materials meet the gradation and other physical specifications. Records of the of QC/QA testing will be maintained throughout the construction and included in the as-built report. Dust and emissions related to crushing, hauling, and placement of the materials will be monitored in accordance with the Air Quality and Emissions Monitoring and Management Plan for the. The geochemical performance and seepage from materials in the Lynx WRSA will be monitored in accordance with the WROMP. 5.8 Contingencies The design includes allowance for the construction of a quarry within the ultimate footprint of the Jay WRSA. This quarry would provide a potential supply of additional rockfill within a shorter haul distance to the Jay Dike construction works, if required to meet material demands. 5-4

28 Section 6, Roads and Laydowns 6 DIKE ROADS AND LAYDOWNS 6.1 Dike Roads The CEMP includes the portion of the roads and laydowns that will be constructed within 30 m of Lac du Sauvage and on islands. The construction of the roads within 30 m of the shoreline (dike roads) will not commence until the Water Licence has been approved and sediment and erosion control measures and monitoring are in place. The rockfill platform portion of the Jay Dike will connect to the Jay Road and Jay North Road at its onshore abutments. The Jay Road and Jay North Road will be constructed to a minimum width of 25.8 m to accommodate two way traffic for CAT 793F haul trucks. The dike roads will be widened, as necessary at the abutments, to transition traffic to the dike. The surficial organic layer, which includes vegetation and organic soil, will not be stripped. Larger boulders on the tundra surface will be removed from the road alignment as necessary to facilitate construction. Where it is necessary to excavate materials from the road foundation, these will be stockpiled within an appropriate area of the Jay WRSA. The dike roads will be constructed from a combination of rockfill and crushed rock, as described in Section 5. Materials will be stockpiled, loaded, hauled, and placed to minimize segregation. The typical dike road profile includes a base layer of rockfill, topped by a 0.5 m layer of 200 mm minus material and a 0.15 m layer of 56 mm minus crushed material. Rockfill and crushed materials will be placed in layers and compacted to form side slopes of approximately 1.3 horizontal to 1 vertical (1.3H:1V). The thickness of the rockfill placed for dike road construction varies depending on the topography, ground conditions, permafrost protection, and road gradients. The minimum thickness of fill will be 1 m. Where the thickness of the fill exceeds 3 m, berms will be constructed along the outer crest for safety as required by Section of the NWT Mine Health and Safety Regulations. Thaw sensitive foundation conditions are not expected near the dike abutments or islands. However, in the event that these are identified, the dike road will be constructed to a minimum total thickness of 2 m. Following construction, the dike roads will be topped-up and maintained, as necessary to account for wear and settlement of the road surface. Settled areas will be brought to grade by placing additional appropriate fill material in the settled area. 6.2 Laydowns There are five laydown areas located in the vicinity of the Jay Dike, as indicated on Map The laydowns provide locations to be used for the temporary storage of equipment, construction materials, and to facilitate construction activities (i.e., batch plants, slurry ponds), if needed. Three of the laydown areas are located onshore and two of the laydown areas are located on islands that are crossed by the Jay Dike. The locations have been selected to be within the Project s proposed disturbance footprint and to minimize disruption to wildlife. In each case, the footprint of the laydown area has been designed to maintain a minimum 30 m offset from waterbodies and the Sub-Basin B Diversion Channel, which is the typical offset adopted for the Ekati mine. The surficial organic layer, which includes vegetation and organic soil, will not be stripped from the laydown area footprint. Larger boulders on the tundra surface will be removed and rockfill will be placed in 6-1

29 Section 6, Roads and Laydowns a nominal thickness of 2 m to create a level working area. 56 mm minus crushed material will be placed on the surface, if required to create a suitable working surface. 6.3 Environmental Considerations The main environmental risks associated with the dike roads and laydowns are: erosion and potential for sediment in runoff; noise and dust from road construction, maintenance, and use for other construction activities; and, interaction with wildlife. 6.4 Management and Controls The dike road and laydown construction and maintenance activities will incorporate the control measures described below. Except where necessary to remove boulders or in areas of soft ground, excavation of the foundation soils will be minimized by placement of fill directly over the natural surface. This will reduce the potential for erosion and sediment in runoff from foundation preparation works. The road and laydown areas will be constructed of rockfill and crushed materials. The rockfill is coarse and relatively resistant to the erosion that typically generates sediment. Clays and natural soils will not be incorporated into the road and laydown construction fill. Material used in construction will be non-pag. Large diesel-powered equipment will be in sound mechanical condition, which will maintain noise and emissions within normal operating levels for this equipment. Maintenance records will be maintained for all construction equipment used on the Project. Spills of diesel fuel, oil, grease, or other hydrocarbons will be cleaned up immediately, and in accordance with the Spill Contingency Plan. Roads and laydown areas will be regularly maintained and dust suppression methods will be implemented (e.g., spraying with water during summer) as appropriate to control dust. All personnel will receive Environmental Awareness Training, which includes instructions on how to appropriately deal with and report wildlife encounters. Wildlife will be monitored and managed in accordance with the Wildlife Effects Monitoring Plan (WEMP) and Caribou Road Mitigation Plan (CRMP). 6.5 Monitoring Monitoring for the road and laydown construction and maintenance will include the tasks listed below. As part of the QC/QA activities, materials will be visually inspected in the stockpile and as they are placed to confirm that they satisfy the specifications. 6-2

30 Section 6, Roads and Laydowns Survey will be carried out to control and verify the lines and levels of all fill materials placed. QA will include review of the survey data and periodic checks on the fill placement for compliance with the design. Dominion Diamond personnel will carry out routine inspections of the roads and construction area to monitor the environmental performance of the work. Wildlife will be monitored in accordance with the WEMP and CRMP. 6.6 Contingencies Erosion and sediment generated from the road and laydown areas is expected to be minimal. Where monitoring indicates erosion or sediment has been generated by these sources, additional controls will be implemented. These controls will depend on the nature of the erosion or release but may include the installation of additional controls such as silt fences. 6-3

31 Section 7, Turbidity Barriers 7 TURBIDITY BARRIER 7.1 Design Turbidity curtains will be used during open-water dike construction to limit the transport of sediments in Lac du Sauvage from the work area to beyond the turbidity barriers. Water currents in Lac du Sauvage are primarily driven by wind conditions. These are highly variable and current speeds and directions vary accordingly. Turbidity barriers are a proven method for controlling turbidity for dredging and in-water construction projects (USACE 2005). They represent BAP for the management of turbidity in lake construction works and have been successfully implemented for similar in-lake construction projects in the NWT and Nunavut. Turbidity curtains can only be installed and maintained in ice-free conditions. The curtains will be deployed and maintained for all dike fill placement works carried out during the open-water season (July to early October). These activities will take place over three years, from 2017 to Construction activities during the open-water season will not proceed until the turbidity barrier systems for the work area are in place. The efficacy of turbidity barriers depends on several factors including the quantity and type of material in suspension, currents, wind and wave action, and the method of deployment. It is important that these factors be adequately considered in design of the turbidity barrier system. Turbidity barriers are typically most effective in currents up to 1.5 knots (77 cm/s) but have been designed to control turbidity in currents up to 5 knots (250 cm/s) (USACE 2005). The turbidity barrier system will comprise a system of curtains, flotation systems, and anchors that will act to limit the migration of suspended solids beyond the turbidity barriers within the lake. The system will be designed and installed to withstand a maximum current velocity of up to 1.0 metre per second (m/s) and will be consistent with the United States Army Corps of Engineer Type II or Type III standards for silt curtains. The curtain fabric will be an impermeable coated polyvinyl chloride (PVC) or geomembrane with a minimum unit weight of 610 grams per square metre (g/m 2 ), rated to maintain flexibility to -55 C. A robust anchoring system will be used to hold the curtain in place against wind, wave, and current forces. The turbidity barrier system will be installed in water depths of up to approximately 20 m. The design will incorporate a furling or reefing system that will allow the curtain to be adjusted to follow the lakebed surface. Where the water is up to 3 m deep, the curtain will extend from the lake surface to the lakebed. This will reduce the potential for suspended solids to escape the turbidity barrier due to wave effects near the shoreline. In water exceeding 3 m in depth, the maximum gap between the base of the turbidity curtain and the lakebed surface will be 1 m. A typical installation profile is provided as Figure

32 Section 7, Turbidity Barriers Figure Typical Turbidity Barrier Profile 7-2

33 Section 7, Turbidity Barriers While turbidity curtains are a recognized means of reducing sediment transport, they are rarely 100% effective. Studies have shown that a single turbidity curtain will reduce turbidity in the water column by 80% to 90% (JBF Scientific Corporation 1978). There is also the potential for a barrier to break or become dislodged from its anchor. For these reasons and wherever practicable, Dominion Diamond will install an outer (or secondary) turbidity curtain around the construction works. The outer turbidity barrier will further reduce any residual sediment in the water column. The approximate locations of the inner and outer turbidity barriers for each open-water construction season are shown in Maps 7-1.1, 7.1-2, and Turbidity barrier alignments make use of islands and shallow water areas to reduce exposure to wind and currents, where possible. Where the construction schedule allows, the upstream portion of the Jay Dike rockfill platform will be placed during the winter, such that in the following summer construction season, the inner turbidity curtains can be deployed in smaller cells and anchored to the platform. The rockfill platform will provide protection for the curtains from waves and currents, similar to breakwaters near harbours. The final location of the turbidity barriers will be determined in the field, based on the site conditions and as required to create an effective barrier for suspended sediment transport. The final location of the barriers will be surveyed and recorded in the as-constructed drawings for the dikes. 7-3

34 N:\Client\dominion Diamond\jay Project\99_projects\ \02_PRODUCTION\2090\ _7_1-1.dwg Layout: MAP Modified: TYKlassen 05/12/2016 3:01 PM Plotted: TYKlassen 05/31/ E E N N WASTE ROCK STORAGE AREA E E E E LAC DU SAUVAGE WL LAKEBED SEDIMENT STORAGE AREA N N N N N N JAY ROAD JAY NORTH ROAD NORTH DIKE STORAGE AREA FOR OTHER CONSTRUCTION WASTE N N JAY PIPE E E E E 410 JAY DIKE E E 415 REV PROJECT TITLE DATE LEGEND NOTES 0 SCALE WATERBODY WATERCOURSE REFERENCES MAJOR TOPOGRAPHY CONTOURS JAY LAYDOWN AREAS PREVIOUS CONSTRUCTION WORKS JAY DIKE CONSTRUCTION WORKS PRIMARY TURBIDITY BARRIER SECONDARY TURBIDITY BARRIER 1. ALL UNITS IN METRES UNLESS OTHERWISE NOTED. 2. ELEVATION IN METRES ABOVE SEA LEVEL. 1. CONTOUR AND BATHYMETRIC DATA PROVIDED BY AURORA GEOSCIENCES LTD., FILE: Final 1m Contours - Priority Area.dxf, DATE RECEIVED: OCTOBER 29, WATER OBTAINED FROM CANVEC NATURAL RESOURCES CANADA, COORDINATES ARE SHOWN IN DATUM: NAD 83, PROJECTION: UTM ZONE 12 NOT FOR CONSTRUCTION ,200 REVISION DESCRIPTION DES CADD CHK RVW JAY PROJECT NORTHWEST TERRITORIES, CANADA YEAR 1 - SUMMER CONSTRUCTION TURBIDITY BARRIER LAYOUT PROJECT No. DESIGN CADD CHECK REVIEW FILE No _7_1-1.dwg CM TAK DA JCC SCALE METRES ISSUED FOR FINAL CM TAK DA JCC A ISSUED FOR REVIEW CM TAK - - MAP AS SHOWN

35 N:\Client\dominion Diamond\jay Project\99_projects\ \02_PRODUCTION\2090\ _7_1-2.dwg Layout: MAP Modified: TYKlassen 05/12/2016 3:04 PM Plotted: TYKlassen 05/31/ E E N N WASTE ROCK STORAGE AREA E E LAKEBED SEDIMENT STORAGE AREA N N N N N N JAY ROAD JAY NORTH ROAD NORTH DIKE STORAGE AREA FOR OTHER CONSTRUCTION WASTE E E N N JAY PIPE E E E E LAC DU SAUVAGE WL JAY DIKE E E 415 REV PROJECT TITLE DATE LEGEND NOTES 0 SCALE WATERBODY WATERCOURSE REFERENCES MAJOR TOPOGRAPHY CONTOURS JAY LAYDOWN AREAS PREVIOUS CONSTRUCTION WORKS JAY DIKE CONSTRUCTION WORKS PRIMARY TURBIDITY BARRIER SECONDARY TURBIDITY BARRIER 1. ALL UNITS IN METRES UNLESS OTHERWISE NOTED. 2. ELEVATION IN METRES ABOVE SEA LEVEL. 1. CONTOUR AND BATHYMETRIC DATA PROVIDED BY AURORA GEOSCIENCES LTD., FILE: Final 1m Contours - Priority Area.dxf, DATE RECEIVED: OCTOBER 29, WATER OBTAINED FROM CANVEC NATURAL RESOURCES CANADA, COORDINATES ARE SHOWN IN DATUM: NAD 83, PROJECTION: UTM ZONE 12 NOT FOR CONSTRUCTION ,200 REVISION DESCRIPTION DES CADD CHK RVW JAY PROJECT NORTHWEST TERRITORIES, CANADA YEAR 2 - SUMMER CONSTRUCTION TURBIDITY BARRIER LAYOUT PROJECT No. DESIGN CADD CHECK REVIEW FILE No _7_1-2.dwg CM TAK DA JCC SCALE METRES ISSUED FOR FINAL CM TAK DA JCC A ISSUED FOR REVIEW CM TAK - - MAP AS SHOWN

36 N:\Client\dominion Diamond\jay Project\99_projects\ \02_PRODUCTION\2090\ _7_1-3.dwg Layout: MAP Modified: TYKlassen 05/12/2016 3:05 PM Plotted: TYKlassen 05/31/ E E N N WASTE ROCK STORAGE AREA E E LAKEBED SEDIMENT STORAGE AREA N N N N N N JAY ROAD JAY NORTH ROAD NORTH DIKE STORAGE AREA FOR OTHER CONSTRUCTION WASTE E E N N JAY PIPE E E JAY DIKE E E LAC DU SAUVAGE WL E E 415 REV PROJECT TITLE DATE LEGEND NOTES 0 SCALE WATERBODY WATERCOURSE REFERENCES MAJOR TOPOGRAPHY CONTOURS JAY LAYDOWN AREAS PREVIOUS CONSTRUCTION WORKS JAY DIKE CONSTRUCTION WORKS PRIMARY TURBIDITY BARRIER SECONDARY TURBIDITY BARRIER 1. ALL UNITS IN METRES UNLESS OTHERWISE NOTED. 2. ELEVATION IN METRES ABOVE SEA LEVEL. 1. CONTOUR AND BATHYMETRIC DATA PROVIDED BY AURORA GEOSCIENCES LTD., FILE: Final 1m Contours - Priority Area.dxf, DATE RECEIVED: OCTOBER 29, WATER OBTAINED FROM CANVEC NATURAL RESOURCES CANADA, COORDINATES ARE SHOWN IN DATUM: NAD 83, PROJECTION: UTM ZONE 12 NOT FOR CONSTRUCTION ,200 REVISION DESCRIPTION DES CADD CHK RVW JAY PROJECT NORTHWEST TERRITORIES, CANADA YEAR 3 - SUMMER CONSTRUCTION TURBIDITY MONITORING LOCATIONS PROJECT No. DESIGN CADD CHECK REVIEW FILE No _7_1-3.dwg CM TAK DA JCC SCALE METRES ISSUED FOR FINAL CM TAK DA JCC A ISSUED FOR REVIEW CM TAK - - MAP AS SHOWN

37 Section 7, Turbidity Barriers 7.2 Deployment and Removal The turbidity barrier systems will be deployed in July each year, as soon as ice-free conditions permit, and before the commencement of construction in a given area. They will be removed before ice formation in October. Bottom anchors, end anchors, and buoys will be installed to provide a structure for deployment of the turbidity curtain. Bottom anchors and buoys may be deployed by positioning on the ice, before ice break-up, by deployment from the water using a barge and tug in the lake, or by another suitable means. The placement method will be carefully sequenced. End anchors will be secured to the islands, abutments, or the dike itself. The turbidity curtains will only be installed in weather and current conditions that are safe and will not result in damage to the curtain. The furled curtain will be positioned and secured in place before unfurling. A furling or reefing system will be used to adjust the length of the curtain to follow the lakebed bathymetry. The curtain will be inspected before installation, following installation and daily throughout the construction season. In the event of damage, repairs will be made or segments of the curtain replaced. Damaged or removed sections will be disposed of in accordance with the Waste Management Plan. Turbidity barriers will be removed at the end of each open-water construction season, before ice formation, or as sections of the dike construction are completed. 7.3 Environmental Considerations The main environmental risks associated with deployment and use of the turbidity barrier systems are: the turbidity curtain is not installed to the required depth, allowing the escape of sediment beneath the curtain; damage to the turbidity barrier allows the release of sediment; and, portions of the turbidity barrier remain in the lake. 7-7

38 Section 7, Turbidity Barriers 7.4 Controls The turbidity barrier design will incorporate the control measures described below. The curtains will be deployed in water depths up to approximately 20 m. Where water depths are 3 m or less, the curtains will extend to the lakebed surface. Where water depths exceed 3 m, a maximum of 1 m gap between the base of the curtain and the lakebed surface will be permitted. Where the construction schedule allows, the upstream portion of the Jay Dike rockfill platform will be placed during the winter, such that in the following summer construction season, the inner turbidity curtains can be deployed in smaller cells and anchored to the platform. The rockfill platform will also provide protection for the curtains from waves and currents, similar to breakwaters near harbours. Where possible, the turbidity barrier alignments will make use of islands and shallow water areas to reduce exposure to wind and currents. To the extent that it is practical, the Project will employ a double turbidity barrier, comprising an outer barrier installed beyond the inner turbidity barrier. The turbidity barrier will be designed to withstand lake currents up to 100 cm/s. This is 2.5 times greater than the highest lake current predicted for the construction area using the 2009 to 2013 wind data. The turbidity barrier will incorporate, UV resistant, impermeable curtains with low temperature flexibility. The curtains, anchoring and support system will be appropriate for the anticipated storm events. The Contractor will maintain on site sufficient spare parts and equipment to allow repair or replacement of damaged barrier sections. 7.5 Monitoring The following monitoring will be carried out during installation, operation, and removal of the turbidity barriers: The Contractor will survey and provide as-built details for the installed turbidity barrier alignments to be reviewed by the Engineer and Owner; All barriers will be inspected daily by the Contractor and following any large wind events; Monitoring of turbidity (as an indicator of TSS concentration) will be used to assess the effectiveness of the turbidity barrier and to determine the need for adjustments and/or additions (Appendix A). 7.6 Contingencies Additional turbidity barriers will be available for deployment to address local problems or to install a parallel barrier in certain areas, if necessary. 7-8

39 Section 8, Jay Dike Fill Placement 8 JAY DIKE FILL PLACEMENT, EXCAVATION, AND FOUNDATION PREPARATION 8.1 Overview The majority of Jay Dike construction activities will occur within Lac du Sauvage, before dewatering, with only limited construction occurring in the dry (i.e., above water or on land). On-land construction will be limited to the dike abutments at the shoreline of Lac du Sauvage and on the islands that the dike crosses. The Jay Dike will be constructed using haul trucks, bulldozers, excavators and other large earth moving equipment. Light vehicles, water trucks, portable toilet facilities, offices and lunch rooms will be provided, as necessary, to support the construction works. The Jay Dike will be constructed from a combination of rockfill and crushed waste rock (coarse filter and fine filter). A simplified section showing the typical dike geometry is included as Figure Figure Typical Dike Construction Section El = elevation; MIN. = minimum; m = metre. 8-1

40 Section 8, Jay Dike Fill Placement 8.2 Construction Method Rockfill Placement Where the dike is constructed within Lac du Sauvage, rockfill will be placed directly on the lakebed surface. Before placement in the water, rockfill will be dumped on the crest of the dike and pushed over the crest by a bulldozer or other suitable equipment. End dumping of rockfill directly into the water will not be allowed. Oversized rockfill (nominally greater than 1 m) will be placed outside of the extents of the central trench to facilitate subsequent excavation. Rockfill will be placed in two configurations, depending on the dike location. In some areas a single rockfill platform will be constructed. The centre portion of the rockfill platform will then be excavated to allow placement of a crushed rock filter zone. In other areas, double, parallel rockfill platforms will be constructed with sufficient space between the platforms to accommodate the crushed-rock filter zone. In both configurations, the width of the dike will be sufficient to safely accommodate the construction activities in addition to two-way haul traffic. Rockfill will be placed in both the summer and winter construction seasons. In summer, rockfill will be placed in open water, when no ice exists on the lake. Turbidity barriers will be the principal method used to control the transport of suspended sediment generated from rockfill placement during the summer months. Winter rockfill placement will not proceed until ice cover is present on the lake. Ice cover eliminates the ability of wind to generate currents in the lake. Without lake currents, turbidity generated from construction activities is far less mobile. This method of turbidity control has been successfully demonstrated for construction in northern lakes at the Meadowbank Mine in Nunavut. In general, the upstream portion of the rockfill platform will be placed during the winter with the remaining portion of the rockfill platform placed during the summer construction season. During winter, a slow rate of placement will be used to minimize the generation of turbidity within the lake. Multiple rockfill placement fronts will be developed to allow sufficient time for turbidity to dissipate between placed loads. These multiple working fronts will increase the amount of rockfill that can be placed during the winter construction season. The winter placement rate will be modified, if necessary, based on turbidity measurements (as an indicator of TSS concentration). The proposed measurement locations and threshold levels are provided in Appendix A Excavation Excavation will commence behind the advancing rockfill platform placement front, during each summer construction season. Where a single rock platform has been constructed, a central trench will be excavated through the rockfill and foundation soils, to the target elevation on competent soil or bedrock. Where a double platform exists, the lakebed sediments and soils between the platforms will be excavated down to competent soil or bedrock. 8-2

41 Section 8, Jay Dike Fill Placement Excavated rockfill that is free of fines, will be transported to the rockfill placement front, and re-used to build the platform. Rockfill mixed with excavated lakebed sediment and soil will be hauled to and placed within the Jay WRSA. Soft soils, ice rich soils, or those with a high water content, including the upper and consolidated lakebed sediments, will be disposed of within the Lakebed Sediment Storage Area, in the Jay WRSA. The Lakebed Sediment Storage Area is located centrally, within the ultimate footprint of the Jay WRSA, which is itself a minimum of 100 m from the Lac du Sauvage shoreline. The area has been designed to contain soft and weak soils, and their runoff and seepage. Materials stored in the Lakebed Sediment Storage Area will be buttressed by competent waste materials from construction and later encapsulated by waste rock generated from pre-stripping and mining activities. Above-water excavation and foundation preparation activities will include the removal of vegetation, organics, snow, and ice. Vegetation and topsoil stripped from the islands and abutments will be stockpiled within a designated organic stockpile area Fine and Coarse Filter Placement The fine and coarse filter will be placed in the central trench formed between the two rockfill platforms, as shown in Figure The Engineer will inspect and approve the base of excavation and foundation preparation work, before placement of fine and coarse filters. Fine and coarse filter will be placed in a manner that minimizes segregation. Depending on the location of placement, this may include lowering materials into place using an excavator bucket or pushing them down-slope from the crest. The placement front for the coarse filter material is expected to advance closely behind that of the fine filter as the central trench is backfilled. Following placement, the fine filter will be densified, to facilitate excavation of the slurry trench for cut-off wall construction. It is anticipated that a combination of dynamic and vibro-densification may be used to achieve the required density. 8.3 Environmental Considerations The main environmental risks associated with material placement, excavation and foundation preparation activities within the lake are: Material placement, excavation, and foundation preparation activities within the lake will generate suspended sediments; Dust may be generated from the transport of personnel, materials, and equipment on access roads; There is the potential for interaction with wildlife, including caribou, on haul roads or in construction areas; Excavated lakebed sediments and soils, with high water content, may be difficult to contain during transport and storage, resulting in the release of sediment; 8-3

42 Section 8, Jay Dike Fill Placement Excavation spoil, including lakebed sediments, placed in the Jay WRSA may become unstable, erode, or release runoff containing sediments that could enter Lac du Sauvage or nearby watercourses; Runoff from above-water stripped areas of the dike foundation may transport sediment into Lac du Sauvage; Hydrocarbon spills can occur from the operation of diesel powered heavy earthmoving equipment and refuelling; Noise and diesel fumes will be generated by heavy earthmoving equipment; and, Sewage and refuse will be generated by construction area toilet facilities and lunch rooms. 8.4 Management and Controls The material placement, excavation, and foundation preparation activities will incorporate the control measures described below. Two turbidity barriers will be installed to limit the movement of suspended sediments generated from summer construction activities (see Section 7). Turbidity barrier systems and the monitoring program will be in place before the commencement of construction activities that could generate turbidity. Winter rockfill placement will commence once there is sufficient ice cover on the lake, to reduce wind generated currents. Ice cover eliminates the ability of wind to generate currents in the lake. Without the wind generated lake currents, turbidity generated from construction activities is less mobile. This method of turbidity control has been successfully demonstrated for construction in northern lakes at the Meadowbank Mine in Nunavut. Winter rockfill placement rates will be adjusted, as necessary based on turbidity measurements, to maintain compliance with the threshold levels provided in Appendix A. Multiple rockfill placement fronts will be maintained to allow sufficient time for turbidity to dissipate in a particular area before the placement of subsequent loads. Haul trucks with tailgates will be used, if required, to contain wet lakebed sediments during transport. If substantial spillage occurs on the road between the dike and WRSA, it will be cleaned up, as deemed necessary. The Jay WRSA incorporates a Lakebed Sediment Storage Area to contain soft and weak sediments from construction activities. The Lakebed Sediment Storage Area is centrally located within the Jay WRSA to manage stability, runoff, and long-term containment of sediments. Stripping of vegetation and topsoil from the dike abutments and islands will only be carried out as required. The time period that stripped foundation areas are exposed to rainfall and runoff will be minimized. Spills of diesel fuel, oil, grease, lubricants, or other hydrocarbons will be cleaned up immediately, and in accordance with the Spill Contingency Plan. 8-4

43 Section 8, Jay Dike Fill Placement All diesel-powered equipment will be in sound mechanical condition, which will maintain noise and emissions within normal operating levels for this equipment. Maintenance records will be maintained for all construction equipment used on the Project. No garbage or refuse disposal will be allowed in the construction area. Personnel will be required to remove all wastes from the construction area for disposal in accordance with the Waste Management Plan. Chemical toilets will be placed in the construction areas in accordance with the Northwest Territories Mine Health and Safety Regulations. These toilets will be cleaned and recharged, as necessary. Materials used in construction will be non-pag. Haul vehicles will be fuelled onshore, where possible. Haul roads associated with dike construction will be regularly maintained and dust suppression methods will be implemented (e.g., spraying with water during summer) as appropriate to control dust. All personnel will receive Environmental Awareness Training, which includes instructions on how to appropriately deal with and report wildlife encounters. Wildlife will be monitored and managed in accordance with the WEMP and CRMP. 8.5 Monitoring The following monitoring will be carried out as part of the material placement, excavation and foundation preparation activities: Monitoring of turbidity (as an indicator of TSS concentration) will be conducted to maintain compliance with the threshold levels provided in Appendix A. Surveys will be conducted and results reviewed by the Engineer to verify the lines and grades of all excavation, foundation preparation, and material placement satisfies the design intent. Dominion Diamond will carry out QC testing of fine filter and coarse filter materials as they are produced to confirm that they meet the requirements of the design. QC records for the construction activities will be maintained by the Contractor and reviewed by the Engineer. Where the base of the excavation is not extended to bedrock, samples from the base of the excavation will be tested in the laboratory, to document the foundation soils. The excavation conditions are to be approved by the Engineer. Excavation activities will be observed by the Engineer. QA will include: observation of the excavation and survey activities; review of the survey data and confirmatory soundings of the trench base; inspection of the materials during excavation and disposal; observation of the fill placement and densification activities, confirmatory testing of the materials; and review of the QC results. The Engineer will also review and approve the foundations before the placement of backfill. 8-5

44 Section 8, Jay Dike Fill Placement Routine inspections of the construction area will be conducted to monitor the environmental performance of the work. The Jay Dike Geotechnical Review Board established by Dominion Diamond will provide an independent review of the design and construction of the proposed Jay Dike. A summary of QA/QC procedures for the Jay Dike is provided in Appendix B. 8.6 Contingencies Additional turbidity barriers will be available for deployment to address local problems or to install a parallel barrier in areas, if necessary. In the event of a spill or release, the Spill Contingency Plan will be activated. 8-6

45 Section 9, Cut-off Walls 9 CUT-OFF WALL 9.1 Overview The Jay Dike is designed with a composite low-permeability element that will be constructed through the fine filter, and foundation soils (where present) and extend into the shallow bedrock. This low-permeability element of the Jay Dike, in combination with the construction of the North Dike, is designed to allow dewatering of the isolated area of Lac du Sauvage that contains the Jay kimberlite pipe. During operations, these elements of the design will also reduce seepage into the mining area to a manageable level such that open pit mining can occur. The composite low-permeability element consists of a CSB cut-off wall, extended to bedrock, or competent soil. Where the cut-off wall does not extend to bedrock, jet grout columns will be constructed to extend the low permeability element to bedrock. Curtain grouting will be conducted in the shallow bedrock and at the interface of the bedrock and cut-off wall or jet grout columns. Typical cross-sections showing the low permeability elements of the Jay Dike are provided in Figure Figure Jay Dike Low Permeability Element Typical Cross-Sections CSB = cement-soil-bentonite; m = metre. The CSB cut-off wall will be constructed through the densified fine filter within the rockfill platform. The cut-off wall designed as a vertical continuous wall that will be resistant to erosion and piping with a minimum width of 1.0 m. The cut-off wall will extend to bedrock, competent soil, or frozen ground. 9-1

46 Section 9, Cut-off Walls 9.2 Construction Method Cut-off wall construction is intended to take place towards the end of each summer construction season (nominally September to early October), once the fine filter has been densified and while weather conditions allow the bentonite slurry to not freeze. The cut-off wall construction involves the following steps: 1) Excavate the cut-off wall trench through densified fine filter to bedrock or to the target elevation using slurry trench technology (Photo 9.2-1), ensuring the trench remains filled with a bentonite slurry; 2) Dispose of excavation spoils within the Jay WRSA; 3) Survey the base of the trench elevation, for Engineer approval; and, 4) Prepare CSB material in a batching plant for transport and placement within the excavated trench. Photo Typical Cut-Off Wall Excavation Using Slurry Trench Technology Bentonite slurry will be prepared in batches and allowed to hydrate. The bentonite slurry will be mixed using a high-shear mixer and will be held in storage ponds or tanks in quantities sufficient to supply the works and maintain the level of slurry within the trench. While in storage, the bentonite slurry will be agitated or recirculated to maintain a homogeneous mixture. 9-2

47 Section 9, Cut-off Walls Tanks and ponds used to mix and hold the bentonite slurry will be located on the dike, nearby islands, or dike abutments in the vicinity of the excavation works. They will be lined and operated with sufficient freeboard to prevent the release of bentonite slurry. Tanks will be appropriately positioned to avoid areas of high traffic movement or with appropriate isolation measures in place. Pumps, valves, hoses, and supply lines used to pump slurry into the trench will be inspected daily for wear and leaks and will be maintained or replaced as necessary. Spoil from the excavation will comprise mainly fine filter material and residual bentonite slurry. The spoil will be hauled to the Jay WRSA and disposed of within an appropriate area, depending on its consistency. It is anticipated this material will be disposed of within the Lakebed Sediment Disposal Area of the WRSA. Trucks with tailgates will be used to transport material, if conditions warrant. The cut-off trench will backfilled with CSB in a continuous operation, following behind the trench excavation. One potential backfill method is schematically depicted in Figure The backfill of the trench will be monitored to maintain separation between the excavation and backfill fronts. Figure Continuous CSB Cut-off Wall Construction Method CSB = cement-soil-bentonite The CSB backfill will comprise a homogeneous mixture of cement, till, bentonite, and water. The main component of the CSB will be till sourced from pre-stripping of the dewatered portion of Lynx Lake, as part of Lynx mining operations. Till from Lynx Pit pre-stripping will be stockpiled within the Lynx WRSA, before use in construction of the Jay Dike. Cement, bentonite, and water will be added in the proportions required to create a workable material that will meet the strength, permeability, and material handling characteristics of the design. Batching plant(s) will be used to produce a homogeneous CSB mix. A typical batching plant is depicted in Photo

48 Section 9, Cut-off Walls Photo Typical Batching Plant The batching plant will include suitable equipment to measure the proportions of materials being used to produce each batch, and to mix the combined material to form a homogenous mixture. Loading and mixing facilities will be either fully contained or outfitted with dust suppression guards to control dust generation from dry materials. The batching plant will be designed to prevent the release of spills. The batching plant will be located either within one of the five proposed laydown areas in the vicinity of the Jay Dike or other suitable area. The CSB will be transported to the cut-off trench either using mixer trucks, a pipeline, or other suitable means. 9-4

49 Section 9, Cut-off Walls 9.3 Environmental Considerations The main environmental risks associated with the cut-off wall installation are as follows: spilled bentonite slurry or CSB could enter into the lake; minor dust releases could occur when mixing bentonite or cement; and, hydrocarbon spills could occur from the operation of heavy equipment and refuelling. 9.4 Management and Controls The cut-off wall construction will incorporate the control measures described below. Tanks and ponds used to mix and hold the bentonite slurry will be lined and operated with sufficient freeboard to prevent overtopping. Tanks will be appropriately positioned to avoid collisions with heavy earthmoving equipment. Pumps, valves, hoses, and supply lines used to pump slurry into the trench will be inspected daily for wear and leaks and will be maintained or replaced, as necessary. Before the initiation of work, the Contractor will demonstrate that the CSB batching plant satisfies the environmental and quality standards for operation, maintenance, and cleaning. CSB will be prepared to the consistency of a paste rather than fluid. This relatively dry consistency means that spills of this material are unlikely to travel far from the source. Haul trucks with tailgates will be used, if required, to transport excavated spoils to the Jay WRSA. Where appropriate, based on consistency, excavated material will be disposed of in the Lakebed Sediment Disposal Area of the Jay WRSA. The Lakebed Sediment Disposal Area has been designed to contain soft and wet materials from construction within a central area of the Jay WRSA. Loading and mixing facilities for the batching plant will be either fully contained or outfitted with dust suppression guards to control dust generation from dry materials. Dry bentonite and cement will not be poured from height to minimize dust releases. All waste, wash water, and unused CSB will be disposed of in accordance with the Waste Management Plan. Spills of diesel fuel, oil, grease, or other hydrocarbons will be cleaned up immediately, and in accordance with the Spill Contingency Plan. 9-5

50 Section 9, Cut-off Walls 9.5 Monitoring The following monitoring activities will be carried out during the cut-off wall construction: Daily records will be maintained including: records of all samples taken and tests performed; record of soundings taken during construction; signed cut-off wall foundation approval forms; record of material quantities (CSB and slurry); and, as-built profile drawing of trench bottom and CSB backfill location. QC/QA testing will be carried out on the bentonite slurry and CSB backfill to demonstrate that they satisfy the design specifications. QA will be carried out by the Engineer and will include observations, testing, and foundation approval. The Jay Dike Geotechnical Review Board established by Dominion Diamond will provide an independent review of the design and construction of the proposed Jay Dike. 9.6 Contingencies In the event of a spill or release, the Spill Contingency Plan will be activated. 9-6

51 Section 10, Jet Grouting 10 JET GROUTING 10.1 Overview Jet grouting will carried out where necessary to extend the low permeability element to bedrock. Jet grout columns will extend a minimum of 1 m into bedrock and will overlap the constructed CSB cut-off wall by a minimum of 1 m. The jet grouting areas and extent to be treated by jet grouting will be confirmed following construction of the CSB cut-off wall each season. Based on the geotechnical investigations, the areas where jet grouting are expected to be required are shown in Map

52 N:\Client\dominion Diamond\jay Project\99_projects\ \02_PRODUCTION\2090\ _10_1-1.dwg Layout: MAP Modified: TYKlassen 05/12/2016 3:16 PM Plotted: TYKlassen 05/31/2016 LAKEBED SEDIMENT STORAGE AREA E E N N STORAGE AREA FOR OTHER CONSTRUCTION WASTE 415 E E N N N N JAY NORTH ROAD WASTE ROCK STORAGE AREA NORTH DIKE JAY PIPE E E E E JAY DIKE 410 REV PROJECT TITLE DATE LEGEND NOTES 0 SCALE WATERBODY WATERCOURSE REFERENCES MAJOR TOPOGRAPHY CONTOURS MINOR TOPOGRAPHY CONTOURS PREVIOUS CONSTRUCTION WORKS (ROADS AND LAYDOWN AREAS) JAY DIKE JET GROUTING AREAS 1. ALL UNITS IN METRES UNLESS OTHERWISE NOTED. 2. ELEVATION IN METRES ABOVE SEA LEVEL. 1. CONTOUR AND BATHYMETRIC DATA PROVIDED BY AURORA GEOSCIENCES LTD., FILE: Final 1m Contours - Priority Area.dxf, DATE RECEIVED: OCTOBER 29, WATER OBTAINED FROM CANVEC NATURAL RESOURCES CANADA, COORDINATES ARE SHOWN IN DATUM: NAD 83, PROJECTION: UTM ZONE 12 NOT FOR CONSTRUCTION REVISION DESCRIPTION DES CADD CHK RVW JAY PROJECT NORTHWEST TERRITORIES, CANADA PRELIMINARY JET GROUTING AREA PROJECT No. DESIGN CADD CHECK REVIEW FILE No _10_1-1.dwg CM TAK DA JCC SCALE METRES ISSUED FOR FINAL CM TAK DA JCC A ISSUED FOR REVIEW CM TAK - - AS SHOWN MAP

53 Section 10, Jet Grouting 10.2 Construction Method Jet grouting operations will be scheduled to take place outside of the open-water season (i.e., during winter) to avoid conflict with summer construction activities. The jet grouting method consists of the following steps: 1) Closely spaced boreholes will be drilled through the CSB cut-off wall and underlying competent soils at least 1.0 m into the bedrock. 2) High-pressure fluids emanating from nozzles near the base of the grouting rods will be used to erode the soil particles and mix them with the injected fluids. The drill string is rotated as it is raised within the borehole to create columns. 3) Following installation of the primary jet grout columns described above, secondary columns will be installed between the primary columns to form a continuous wall of jet grouted columns. 4) Spoils generated during jet grouting operations will be collected and disposed within an appropriate area of the Jay WRSA. The performance and environmental outcomes for this method of grouting have been successfully demonstrated for other dikes, including the A154 and A418 dikes at the nearby Diavik Diamond Mine, and the Meadowbank Mine in Nunavut. The jet grouting operation will require the following equipment and facilities: generators, light plants, material storage, canvas tents, and/or hordings to allow all-season operation; handling facilities for the cement and bentonite; water tanks, grout mixers, and agitated grout holding tanks; air compressors, pumps and delivery lines to supply grout, air, and water at the required pressures; drill rigs and grout plants; a grout and slurry return recovery system; and, survey for layout and alignment of the drill holes. 10-1

54 Section 10, Jet Grouting 10.3 Environmental Considerations The main environmental risks associated with the jet grouting operations are as follows: grout could spill from the grout batching plant or grout supply lines and flow into the lake; return grout and slurry may be discharged on the surface and flow into the lake; grout may migrate under pressure into the lake through discontinuities in the bedrock or dike fill interfaces at depth; hydrocarbon spills could occur from diesel powered equipment and refuelling; and, minor dust releases could occur when mixing bentonite or cement to prepare grout Management and Controls The grouting operations will incorporate the control measures described below. Activities that involve the storage and handling of fluids will be away from the edge of the dike. The operation, being specialized, will only be undertaken by appropriately qualified operators. The Engineer will review and approve the Contractor s Jet Grouting Plan, QC procedures, equipment condition, material specifications, and calibration sheets. A trial program will be conducted to evaluate the suitability of the Contractor s proposed construction methods. Jet grout columns are to be constructed in a manner that allows continuous spoil return up the borehole annulus during injection. Waste materials will be managed to avoid entering the lake. All waste, wash water, grout, return grout, and drilling fluids will be disposed of in accordance with the Waste Management Plan. The Contractor will carry sufficient spare parts on site to maintain the jet grouting equipment in a satisfactory operating condition at all times. The equipment used for mixing, holding, and pumping grout will be operated to minimize spillage of materials Monitoring The following monitoring will be carried out during jet grouting operations: All jet grouting will be performed in the presence of the Engineer. Daily records will be maintained including: calculated total water/soil/grout volumes forming each column; daily grouting records (e.g., pressure, flow rate, and density of materials); 10-2

55 Section 10, Jet Grouting instrument calibration and calibration checks; additional observations on grout escapes, ground heave/collapse, or other unusual behaviour; and, QC/QA tests. The accuracy of pressure gauges and transducers used with drilling and grouting equipment will be checked daily and be reported to the Engineer weekly. Drill rigs will be equipped with automated controls and instrumentation (i.e., pressure gauges, flow meters, rate of monitor rotation and withdrawal) that allow continuous monitoring and control and automatic recording of data throughout the jet grouting operations. Each rig used for jet grouting will have a Drilling Parameter Recorder to collect and display data in real-time including penetration rate, down thrust pressure, rod torque, rotation rate, drilling fluid pressure, and flow. The Jay Dike Geotechnical Review Board established by Dominion Diamond will provide an independent review of the design and construction of the proposed Jay Dike Contingencies In the event of a spill or release, the Spill Contingency Plan will be activated. 10-3

56 Section 11, Curtain Grouting 11 CURTAIN GROUTING 11.1 Overview Curtain grouting will be carried out along the entire length of the Jay Dike to extend the low-permeability element into the bedrock. It will take place after the installation of the CSB cut-off wall and jet grout wall (where present). Curtain grouting is expected to extend to between 5 and 20 m below the bedrock contact, depending on ground conditions, and the imposed hydraulic head. Curtain grouting will also treat the interface between the base of the cut-off wall or jet grout columns and bedrock Construction Method Curtain grouting operations will largely be scheduled outside of the open-water season (i.e., during winter) to avoid conflict with summer construction activities. The curtain grouting method is summarized as follows: 1. Drill and install steel casing 0.5 m into the bedrock through the centerline of the CSB cut-off wall and jet grout wall (where present); 2. Continue to drill into the bedrock until the target curtain grouting depth is achieved; 3. Isolate sections of the hole (i.e., stage) in the bedrock using inflatable packers to: a. conduct water pressure (Lugeon) tests, if required; and, b. pressure inject grout; 4. Clean out the casing after the pressurized grout injection; 5. Perforate the casing at the interface between the bedrock and the CSB cut-off wall or jet grout wall, up to a minimum of 1.5 m above the interface; 6. Isolate the section of perforated casing using an inflatable packer above the highest perforation and pressure inject grout into the interface with the CSB cut-off wall or jet grout wall; and, 7. Tremie backfill the casing with grout mix. Depending on ground conditions, two different curtain grouting methods may be used. The upstage working method involves drilling the grout hole to full depth in the bedrock and grouting the hole from the bottom up in stages. The downstage working method involves drilling to the depth of the uppermost bedrock stage then grouting that stage. After waiting for the grout in the previous stage to set, the process is repeated downwards until the final depth is reached. In general, the upstage method will be utilized; however, where difficult ground conditions are encountered, the downstage method will be used. The curtain grout wall will be installed using the split-spaced closure method, with primary, secondary, and tertiary holes to provide a maximum spacing of 1.5 m between holes. Primary holes will be drilled at an initial wide spacing and then grouted. After the grout in the primary holes is set, the secondary holes (set midway between the primary holes) will be drilled and grouted. This process is repeated for each subsequent order of holes. Quaternary and high order holes may be installed if testing or injection volumes indicates that the tertiary holes do not meet the design criteria. 11-1

57 Section 11, Curtain Grouting The curtain grouting operation will require the following facilities and equipment: generators, light plants, material storage, canvas tents, and hoardings to allow all-season operation; handling facilities for the cement and bentonite; water tanks, grout mixers, and agitated grout holding tanks; pumps and delivery lines to supply grout and drilling water; drill rigs for casing installation and bedrock drilling; casing perforation tools; water pressure testing equipment, including inflatable packers; a grout and slurry return recovery system; and, survey for layout and alignment of the drill holes Environmental Considerations The main environmental risks associated with curtain grouting activities are as follows: grout spills from the grout batching plant or grout supply lines; spills of return water, return grout, drilling mud, and other additives; grout may migrate under pressure into the lake through discontinuities in the bedrock or dike fill interfaces at depth; hydrocarbon spills could occur from diesel powered equipment and refuelling; and, minor dust releases could occur when mixing bentonite or cement to prepare grout Management and Controls The curtain grouting operations will incorporate the control measures described below. All curtain grouting activities will be done in the presence of the Engineer. Activities that involve the storage and handling of fluids will be kept away from the edge of the dike. The operation, being specialized, will only be undertaken by appropriately qualified operators. The Engineer will review and approve the Contractor s Curtain Grouting Plan, QC procedures, equipment condition, material specifications and calibration sheets. Waste materials will be promptly removed from the work platform to avoid leakage to the lake. All waste, wash water, grout, return grout, and drilling fluids will be disposed of in accordance with the Waste Management Plan. 11-2

58 Section 11, Curtain Grouting The Contractor will carry sufficient spare parts on site to maintain the curtain grouting equipment in a satisfactory operating condition at all times. The equipment used for mixing, holding, and pumping grout will be winterized and operated to minimize spillage of materials. Before the initiation of work, all equipment will be tested for leaks and functionality by running of water through the system. Before curtain grouting operations, several grout mix designs of varying thickness will be established from confirmatory trials on site to meet the grout apparent viscosity, bleed, and pressure filtration requirements. The Engineer will review and approve the grout mix designs and modify grout mixes as necessary throughout the duration of the curtain grouting operations based on the results of QA/QC testing and ground response. Grouting of any stage will not be permitted if the grouting equipment, data acquisition systems, and computer are not fully functional. This equipment allows close monitoring of each grouting stage. The potential for the release of grout through bedrock discontinuities will be limited by controlling the mix designs of the grout injected, the thickening sequence for grout injection, the grout injection rate and allowable rate of increase, maximum allowable safe pressure, maximum allowable grout injection rate, and the maximum volume of grout to be injected for each stage. The curtain grouting system will be capable of emergency shut-down while grout is circulating through the system. Operators will be trained in the emergency shut-down procedure Monitoring The following monitoring will be carried out during the curtain grouting operation: Daily records will be maintained that will include drilling logs, grouting records, QC, and water pressure test results. Pressure transducers, pressure gauges, and flowmeters will be calibrated and checked by the Engineer. All curtain grouting operation will have real-time monitoring and data acquisition to collect information on flow rate, pressure, volume, and grout Lugeon value. Bourdon-type pressure gauges will be employed as a back-up system to electronic pressure transducers to monitor grouting pressures. The Engineer will monitor the pressure and grout volumes from the real-time monitoring system to identify loss of grout materials. Adjacent ungrouted holes, their casings, and the surface of the dike will be monitored for the flow of grout. The Jay Dike Geotechnical Review Board established by Dominion Diamond will provide an independent review of the design and construction of the proposed Jay Dike. 11-3

59 Section 11, Curtain Grouting 11.6 Contingencies If grout is observed to flow to the outside of casings or elsewhere along the surface of the dike during curtain grouting, rapid mix thickening or emergency shut-down may be employed to stop the grout flow. In the event of a spill or release, the Spill Contingency Plan will be activated. 11-4

60 Section 12, Instrumentation 12 INSTRUMENTATION 12.1 Instrumentation System Instruments will be installed in the Jay Dike and North Dike to monitor performance during dewatering and operation. Inclinometers and survey monuments will be used to monitor the movement and deformation of the Jay Dike. Thermistors will be installed to monitor thermal conditions within the low permeability element of the Jay Dike and within the structure of the North Dike. Vibrating-wire piezometers will be used to monitor the phreatic level within the Jay Dike, which can be used to estimate flow rates through the cut-off wall and foundation. The instrumentation system for Jay Dike includes the components described below. Single-point and multiple-point vibrating-wire piezometers with stainless steel housing, capable of measuring water pressures up to 350 kilopascals (kpa) or 700 kpa, depending on depth. 16-bead thermistor strings with a 0.2ºC accuracy and nominal resistance of 5,000 units of resistance (ohms) at a temperature of 25ºC. Slope Indicator brand, or equivalent, 85 mm diameter inclinometer casings with biaxial guide grooves and 0.75 m long telescoping couplings. Inclinometers will be protected at surface by steel casing with protective caps. Survey monuments will be incorporated in to the inclinometer casings. Leads from the instruments will be run to data loggers located within insulated instrumentation sheds located periodically along the dike. Instrumentation sheds will be protected from corrosion and anchored to the dike to prevent overturning by wind. A data retrieval system will allow the remote, real-time transfer of instrument readings to the site computer system located outside the Jay Dike area. The system will include either remote telemetry via satellite or an alternative, fixed frequency licensed microwave radio system. The number, type, and final location of the instruments installed in the Jay Dike will be adjusted by the Engineer depending on the conditions encountered during construction. The North Dike will be instrumented with 16-bead thermistor strings with a 0.2ºC accuracy and nominal resistance of 5,000 ohms at a temperature of 25ºC Installation Instrumentation will be installed progressively following completion of curtain grouting activities in each work area of the Jay Dike, and following construction of the North Dike. Instrument readings will have stabilized before the commencement of dewatering. The Engineer will review instrumentation readings to confirm stabilization before dewatering commences. Instruments will be installed through the materials used to construct the Jay Dike and North Dike. The general installation procedure for the instruments is summarized below. 12-1

61 Section 12, Instrumentation 1) Following completion of curtain grouting activities in each area, construction information will be reviewed by the Engineer and specific locations for instruments will be established and located by survey. 2) A borehole of sufficient diameter to accommodate the instrument will be drilled from the crest of the dike to the target instrumentation depth. Where necessary, a temporary casing may be used to prevent collapse of the hole. 3) Readings will be taken from all instrumentation to verify correct functioning immediately before installation, where appropriate. 4) The instrument will be lowered into the borehole to the target depth and the annulus around the instrument backfilled with cement-bentonite grout to surface. Any drill casing remaining in the hole will be removed during installation of the instrument. 5) Protective casings will be installed around inclinometers for protection at surface. 6) Cables for thermistors and piezometers will be encased by PVC conduits laid within trenches and connected to the data loggers. The trenches will be backfilled with fine filter material. 7) The instruments will be monitored and readings allowed to stabilize before the commencement of dewatering Environmental Considerations The main environmental risks associated with instrument installation activities are as follows: grout spills could occur during batching, mixing, or backfilling of the holes; hydrocarbon spills could occur from drill rigs on the dike; strong winds could result in loss of materials into the lake; and, minor dust releases could occur when mixing bentonite or cement to prepare grout Management and Controls The instrument installation activities will incorporate the control measures described below. Grout will be prepared in small batches, as required to fill the instrument holes. The equipment used for mixing, holding, and pumping grout will be operated to minimize spillage. Tremie pipes will be used to direct grout to the base of the hole during backfill. This will reduce the potential for spillage of the grout at surface. Activities that involve the storage and handling of fluids will be kept central along the dike alignment, where possible. 12-2

62 Section 12, Instrumentation Waste materials will be promptly removed from the work area to avoid leakage or transport to the lake. All waste, wash water, grout, return grout, and drilling fluids will be disposed of in accordance with the Waste Management Plan. Instrumentation sheds will be securely anchored to the dike to prevent overturning by wind. Dry bentonite and cement will not be poured from height to minimize dust releases Monitoring The instrument installation activities will be monitored as described below. Detailed installation records will be maintained for each if the instruments and included in the as-built report for the dike. The Engineer will oversee the instrument installation activities. Routine inspections of the construction area will be conducted to monitor the environmental performance of the work Contingencies In the event of a spill or release, the Spill Contingency Plan will be activated. 12-3

63 Section 13, North Dike 13 NORTH DIKE 13.1 Construction Method The north abutment of the Jay Dike starts at a small island just offshore from the Lac du Sauvage shoreline. Between the shoreline and this island is a low-lying marshy area and small channel that could be a persistent source of seepage into the dewatered area. The North Dike will be constructed across this channel to reduce potential inflows into the dewatered area and open pit from this area. The North Dike will have length of approximately 150 m and will be constructed in water depths up to approximately 1 m. Design of the North Dike is currently conceptual and will be reviewed following collection of additional information regarding the foundation conditions in this area. Construction of the North Dike will include excavation and placement of fill materials including a low-permeability element. Construction will be scheduled to take place over approximately six weeks in late winter or early spring when Lac du Sauvage is frozen and ice within the footprint of the dike is grounded on the lakebed surface. This will allow the North Dike construction to be carried out in dry conditions (non-flooded), thereby minimizing turbidity caused by construction of this dike. A section showing the typical North Dike geometry is included as Figure Figure Typical North Dike Construction Section El. = elevation; min. = minimum; m = metre. 13-1