Diavik Diamond Mines (2012) Inc. P.O. Box 2498 Suite 300, 5201 – 50th Avenue Yellowknife, NT X1A 2P8 Canada T (867) 669 6500 F (867) 669 9058
Ms. Violet Camsell-Blondin Chair Wek’èezhíi Land and Water Board Box 32 Wekweeti, NT X0E 1W0
31 December 2014
Re: A21 Construction Environmental Management Plan Version 3.0
On October 15, 2012 the Wek’èezhíi Land and Water Board approved or accepted all of the submission from Diavik Diamond Mines (2012) Inc. (DDMI) in relation to the construction of the A21 dike to allow open-pit mining of the A21 kimberlite pipe. Dike construction was subsequently delayed. We will commence the in-lake components of dike construction in July 2015. Crushing for construction material and road/laydown development has begun.
Attached for your approval is an updated A21 Construction Environmental Management Plan (CEMP) that includes both the Dewatering Management Plan (Part E, Item 2) and the Dredging Management Plan (Part C, Item 6).
Regards,
Gord Macdonald
cc Ryan Fequet (WLWB) Brett Wheler
Attached: A21 Construction Environmental Management Plan – Version 3.0.
Diavik Diamond Mines (2012) Inc. PO Box 2498, Suite 300,5201-50th Avenue, Yellowknife, NT, X1A 2P8, Canada Registered in Canada
A21 DIKE:
CONSTRUCTION ENVIRONMENTAL MANAGEMENT PLAN: 2014 UPDATE
Version 3.0
Prepared by
Diavik Diamond Mines (2012) Inc. Yellowknife, Northwest Territories
31 December 2014
Document# : CSLR-002-0513 R3 Diavik Diamond Mines (2012) Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
INSTRUCTION TO DOCUMENT CONTROL
X Entire document revised. Reissue all pages.
Reissue revised pages only.
STAMP THE SPECIFICATION AS FOLLOWS:
Issued for comments.
Issued for approval.
X Issued for regulatory submissions
Issued for construction.
SPECIFICATION REVISION INDEX
No. Prepared Checked By Project Client Pages Remarks By Date Manager Approved Revised Date Date Date B. Hulsman T. Martin T. Martin Issued for regulatory 0 Aug/07 All Aug/07 Aug/07 Aug/07 applications for A21
N. Ekman T. Martin K. Halisheff Issued for regulatory 1 Jul/12 All Jul/12 Jul/12 Ju/12 applications for A21 2,3, G. 32,33,40,41, Issued for regulatory 2 Macdonald June 2013 63, applications for A21 Jun/13 64,71,72,73,76 G. Issued for regulatory 3 Macdonald Dec 2014 All applications for A21 Dec/14
Summary of Changes for Revision 3:
• Revised construction schedule. • Cut-off wall construction method. • Two open-water seasons of foundation preparation and embankment placement. • DDMI as general contractor. .
Diavik Diamond Mines (2012) Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
TABLE OF CONTENTS Page
1.0 INTRODUCTION ...... 1 1.1 Objective ...... 1 1.2 Definition of Best Management Practices ...... 3
2.0 BACKGROUND AND ASSUMPTIONS ...... 4 2.1 Physical Setting ...... 4 2.1.1 Location and Terrain ...... 4 2.1.2 Climate ...... 4 2.1.3 Lake currents ...... 4 2.1.4 Lakebed ...... 4 2.1.5 Sediment Settling ...... 5 2.1.6 Sediment Settling Implications ...... 6 2.1.7 Constraints ...... 6
3.0 OVERVIEW OF CONSTRUCTION SCOPE AND SCHEDULE ...... 8
4.0 CONSTRUCTION PHASE ORGANIZATION AND RESPONSIBILITIES ...... 10 4.1 Introduction ...... 10 4.2 Overall Project Organization ...... 10 4.3 Responsibilities ...... 12 4.3.1 DDMI ...... 12 4.3.2 BGC/DDMI ...... 12 4.3.3 Specialist Contractor/DDMI ...... 13
5.0 CRUSHING FACILITIES ...... 14 5.1 Crushing and Screening Operations ...... 14 5.2 Production and Schedule ...... 16 5.3 Equipment ...... 16 5.4 Stockpiling ...... 16 5.5 Quality Control ...... 17 5.6 Reporting ...... 18 5.7 Engineering and Gradation Specifications ...... 18
6.0 BATCH PLANT ...... 20
7.0 TURBIDITY BARRIERS ...... 21 7.1 Overview ...... 21 7.1.1 Design and installation ...... 21 7.2 Deployment ...... 25 7.2.1 Installation of End Anchors on Islands, Bottom Anchors and Buoys ...... 25 7.2.2 Turbidity Barrier Installation and Removal ...... 25 7.2.3 Control ...... 26 7.2.4 Contingencies ...... 26
8.0 FOUNDATION PREPARATION ...... 27
Document #: CLSR-002-0513-R3 Page i Diavik Diamond Mines (2012) Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
TABLE OF CONTENTS Page
8.1 Introduction ...... 27 8.2 Conventional excavation ...... 27 8.2.1 Overview ...... 27 8.2.2 Equipment ...... 28 8.2.3 Operating Procedures ...... 28 8.2.4 Controls ...... 29 8.2.5 Contingencies ...... 29 8.3 Hydraulic Dredging ...... 29 8.3.1 Overview ...... 29 8.3.2 Installation ...... 29 8.3.3 Operating Procedures ...... 32 8.3.4 Controls ...... 35 8.3.5 Contingencies ...... 35 8.4 Environmental issues ...... 36 8.5 Management Measures ...... 37 8.5.1 Monitoring and Controls ...... 38 Drainage and Piping ...... 38 8.6 38
9.0 A21 DIKE EMBANKMENT PLACEMENT ...... 39 9.1 Overview ...... 39 9.2 Construction Methods ...... 39 9.3 Controls ...... 40 9.4 Environmental Issues ...... 41 9.4.1 Management Measures ...... 41 9.4.2 Monitoring and Controls ...... 42
10.0 CUT OFF WALL - CONSTRUCTION ...... 43 10.1 Overview ...... 43 10.2 Equipment Installations ...... 45 10.3 Operating procedures ...... 46 10.4 Contingencies ...... 47 10.5 Environmental Issues ...... 47 10.5.1 Management Measures ...... 47 10.5.2 Monitoring and Controls ...... 47
11.0 GROUTING EXECUTION ...... 48 11.1 Overview ...... 48 11.2 Jet grouting ...... 48 11.2.1 Method ...... 48 11.2.2 Execution ...... 49 11.2.3 Operation procedures ...... 50 11.2.4 Controls ...... 50 11.2.5 Contingencies ...... 50 11.3 Curtain Grouting ...... 50 11.3.1 Methodology ...... 50
Document #: CLSR-002-0513-R3 Page ii Diavik Diamond Mines (2012) Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
TABLE OF CONTENTS Page
11.3.2 Installation ...... 51 11.3.3 Operating procedures ...... 51 11.4 Controls ...... 51 11.5 Contingencies ...... 52 11.6 Environmental Issues ...... 52 11.6.1 Management Measures ...... 52 11.6.2 Monitoring and Controls ...... 52
12.0 FISH SALVAGE ...... 54 12.1 A21 Fish Salvage Program ...... 54
13.0 A21 – REGULATORY SAMPLING – DIKE CONSTRUCTION ...... 56 13.1 Daily Sampling ...... 56 13.1.1 Remote Monitoring ...... 58 13.2 Plume Delineation Monitoring ...... 58 13.3 Sediment Deposition Monitoring ...... 59
14.0 POOL DEWATERING ...... 62 14.1 Objective ...... 62 14.2 Overview of Dewatering Activities ...... 62 14.2.1 Dewatering Concept ...... 62 14.2.2 A21 Pool Dewatering ...... 62 14.2.3 Regulatory Activities ...... 64 14.3 Pool Water Volumes and Distribution ...... 65 14.3.1 Water Volumes ...... 65 14.3.2 Water Distribution and Storage ...... 65 14.3.3 Water System Layout ...... 66 14.3.4 Pump-out Rates ...... 66 14.4 Discharge Structures ...... 69 14.4.1 On-Land Storage Facilities ...... 69 14.4.2 Lac de Gras ...... 69 14.4.3 Inspections ...... 70 14.5 Monitoring ...... 70 14.5.1 Water License Discharge Criteria to Lac de Gras ...... 70 14.5.2 SNP Sampling Program ...... 72 14.6 Management Plans ...... 73 14.6.1 Site Responsibilities ...... 73 14.6.2 Decision Making ...... 73 14.6.3 Fuel Handling ...... 74 14.6.4 Wildlife Management ...... 74 14.6.5 Environmental Issues ...... 75 14.6.6 Management Measures ...... 75 14.6.7 Monitoring and Controls ...... 75 14.7 Summary Report ...... 75
15.0 SPILL RESPONSE ON LAND AND IN LAC DE GRAS ...... 77
Document #: CLSR-002-0513-R3 Page iii Diavik Diamond Mines (2012) Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
TABLE OF CONTENTS Page
15.1 Spill Response On-land ...... 77 15.2 Spill Report Form ...... 80 15.3 Spill Response in Lac de Gras by Contractor ...... 81
LIST OF FIGURES
Figure 1.1: A21 Dike General Site Plan ...... 2 Figure 1.2: A21 Dike: South Island Construction Facilities Layout ...... 3 Figure 2.1: TSS vs. Time and Depth as A Percentage of Original Value ...... 6 Figure 3.1: A21 Dike Construction Schedule (Gannt Chart) ...... 9 Figure 4.1: Overall Project Organization ...... 11 Figure 7.1: Turbidity Barrier Plan - 2016 ...... 22 Figure 7.2: Turbidity Barrier Profile - 2016...... 23 Figure 7.3: Turbidity Barrier Sections and Details - 2016 ...... 23 Figure 8.1: Lakebed Foundation Preparation Plan ...... 28 Figure 8.2: 16-Inch Cutter Suction Dredge ...... 30 Figure 8.3: 16-Inch Cutter Suction Dredge Layout Plan ...... 30 Figure 8.4: Dredging Pipeline Alignments ...... 31 Figure 9.1: Typical Dike Design Section ...... 39 Figure 10.1: Typical CSM Pre-drill and backfilling...... 43 Figure 10.1: Location of CSM mix plants for A21operations ...... 45 Figure 11.1: Jet Grouting Working Procedure ...... 49 Figure 13.1: Sediment Trap Details ...... 60 Figure 13.2: Flow Chart for The Regulatory Control of Total Suspended Solids ...... 61 Figure 14.1: Floating Discharge Facilities for Direct Discharge to Lac de Gras ...... 63 Figure 14.2: Dewatering Pipeline Alignments ...... 67 Figure 14.3: Elevation vs. Storage Volume for A21 Pool ...... 68 Figure 14.4: Range of Pump-Out Rates During Direct Discharge Phase to Lac de Gras ...... 69 Figure 15.1: Spill Reporting Procedures Charts – Construction Phase ...... 84
LIST OF TABLES
Table 3.1: Construction Scope and Schedule Summary ...... 8 Table 8.1: Target TSS Concentrations for Protection of Adult and Juvenile Fish ...... 36 Table 9.1: TSS Minimization Methods during Embankment Construction ...... 40 Table 10.1: CSM Wall Construction Issue Mitigation Options ...... 46 Table 13.1: Fixed Sampling Locations ...... 56 Table 13.2: Sample Format for Daily Reporting – Fisheries Authorization ...... 57 Table 13.3: Sample Format for Daily Reporting – Water License ...... 57 Table 13.4: Sample Table for Plume Delineation Statistics ...... 59 Table 13.5: Sediment Trap Locations ...... 59
Document #: CLSR-002-0513-R3 Page iv Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
1.0 INTRODUCTION
1.1 Objective The Diavik Diamond Project encompasses the development of the A154, A418 and A21 kimberlite pipes located beneath Lac de Gras.
The initial construction included a large array of structures, including the construction of the A154 dike in Lac de Gras and all other facilities which made possible the mining operations of the diamond bearing A154 North and South kimberlite pipes. Other structures included temporary and permanent accommodations, several on-land processed kimberlite containment structures, a sedimentation pond, a rock quarry, linear developments such as access roads, pipelines, power lines, a runoff water treatment plant, and sewage treatment and outfall.
Subsequent to the completion of the A154 dike the A418 dike was constructed. The A418 dike was completed in the last quarter of 2006. The A418 pool was dewatered and stripping of overburden has commenced. Like the A154 dike, the A418 dike is meeting design expectations.
Construction of the A21 water retention dike will be carried out to allow the exploitation of the A21 kimberlite pipe. It too will be constructed in Lac de Gras using the same design template as were successfully used for the construction of the A154 and A418 dikes. Ancillary facilities will be limited to the construction of small stretches of new access roads, a causeway between East and A21 Islands, new rockfill laydown and fill stockpile areas, power lines and pipelines and the relocation of existing temporary facilities. The general overall site development is presented in Figure 1.1 and ancillary facilities for the A21 dike in Figure 1.2.
This document outlines the Construction Environmental Management Plan (CEMP) to be implemented to minimize environmental effects during the A21 dike construction activities. Diavik Diamond Mines (2012) Inc. (DDMI) is committed to implementing Best Management Practices (BMP) for these activities. A description of each on-land construction activity such as crushing and batching, and in-lake construction activity such as dredging, embankment placement, cut-off wall construction and pool dewatering is provided. Environmental management controls available to the constructors are described. Finally monitoring and inspection programs are described which are compatible with the described BMP and which would provide relevant performance measurement.
Document#: CLSR-002-0513-R3 Page 1 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 1.1: A21 Dike General Site Plan
Document#: CLSR-002-0513-R3 Page 2 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 1.2: A21 Dike: South Island Construction Facilities Layout
1.2 Definition of Best Management Practices The Best Management Practice (BMP) comprises the selection of construction methods and management controls which will be used to minimize, to the extent practical, the environmental impact of the construction activities.
The criteria for establishing the BMP include the following construction methods:
• Use proven technology;
• Be consistent with recommendation by qualified experts;
• Have limited impact on schedule; and
Document#: CLSR-002-0513-R3 Page 3 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
• Be practical given the site conditions.
Monitoring methods must facilitate the implementation of BMP and enable timely responses to incidents.
2.0 BACKGROUND AND ASSUMPTIONS
2.1 Physical Setting 2.1.1 Location and Terrain
The mine site lies just north of the tree line, approximately 200 km south of the Arctic Circle. Classified as a polar desert, this area is located in the zone of continuous permafrost. East Island (the project site) lies within a group of islands located near the east end of Lac de Gras. The northern half of the island is mostly covered by till deposits while the southern half is mostly exposed granitic bedrock with minor till occurrences. The kimberlite pipes which lie just off shore of the east and southeast parts of the island will be mined by open pit and if economical underground mining methods. The A21 kimberlite pipe is located to the east of South Island, which as shown on Figure 1.1 is a smaller island immediately to the south of East Island which hosts all existing mine infrastructure. The A21 dike will tie into South Island on both abutments.
2.1.2 Climate
East Island and South Island lie within the Arctic Climatic Region. The mean annual precipitation is about 375 mm, approximately 40% of which falls as rain. Snow cover exists for about six months of the year, with a maximum thickness of 500 to 650 mm. Most of the snowfall is blown into hollows and depressions, leaving much of the higher ground exposed during the winter. The mean annual air temperature is about -12ºC, with a maximum monthly temperature of about 10ºC in July and a minimum monthly temperature of -35ºC in January. The mean annual ground temperatures vary between -3ºC to -7ºC, depending upon the ground surface cover, topography and the location with respect to larger water bodies. The construction season for in-lake activities will be limited to the ice free period from July to October unless an early start can be made by breaking the ice.
2.1.3 Lake currents
The lake currents have been measured over two summers and one winter by recording current meters at 21 stations in the vicinity of the project during the environmental baseline programs in 1997-1998. These measurements and the values obtained from simulation by mathematical models have demonstrated that the currents are entirely wind induced. The current directions vary according to wind direction and velocities up to 25 cm/sec have been recorded.
2.1.4 Lakebed
The geotechnical characteristics of the lakebed sediments were established during detailed site investigations carried out in 1997 and 1998 (EBA, 1997b and 1998a), and are summarized in the water retention dikes final design report (NKSL, 2004). Further work was undertaken along the A21 dike alignment as documented by Golder (2006a, 2006b, 2007) based on sonic drilling, piezocone, ground penetrating radar (GPR), and laboratory testing programs undertaken in 2006 and 2007, which confirmed the characteristics identified for the lakebed sediments in the
Document#: CLSR-002-0513-R3 Page 4 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
previous studies. Based on the A154 and A418 experience it is well-established that the lakebed sediments are amenable to dredging.
The shoreline of Lac de Gras are dominated by boulders (>30 cm in diameter) which descend to a maximum depth of 6 m.
The lakebed sediment consists of a veneer of very soft sandy silt that covers a competent till followed by bedrock. Lakebed sediment thickness varies generally between 0 and 3 meters with a maximum observed thickness of about 6 meters. The majority of lakebed sediments are derived from the erosion of till and exposed bedrock located along the lakeshore.
The first 0.5 meters of the sediment layer is near fluid. Thereafter it becomes denser with depth. The A154 and A418 experiences show that a cutter suction dredge can remove the sediment. Moreover; this construction method would facilitate the transportation of the sediments to the containment facility.
Index Properties of Lakebed Sediment
Description Silty Sand
Plasticity None
Dry Density, t/m3 Average Range
0 - 0.5 m 1.03 0.48 to 1.63 0.5 - 2.5 m 1.47 0.56 to 1.92
Estimated in-situ sediment density (wet) 1747 kg/m3
Ratio of weight of water to weight of solids 0.456
Shear Strength, kPa Average Range
0 - 0.5 m 2 0 to 10 0.5 - 2.5 m 6 1 to 25
2.1.5 Sediment Settling
The A154 sediment settling observations concur with the results of the two settling columns tests (see Figure 2.1) carried out in the laboratory of EBA Engineering Consultants Ltd. in Edmonton. The results were reported in an internal report entitled “Column Settling Test results Evaluation” by NKSL.
Document#: CLSR-002-0513-R3 Page 5 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 2.1: TSS vs. Time and Depth as A Percentage of Original Value
a) Column 1 (empirical data) b) Column 2 (empirical data)
2.1.6 Sediment Settling Implications
The primary uncertainty with respect to turbidity during dike construction relates to the amount of sediment that could be re-suspended during dredging of bottom sediments prior to beginning dike construction. To account for this uncertainty, DDMI has developed a plan to use turbidity barriers and numerous other management practices to reduce sediment release during dike construction (see Section 6.0, Turbidity Barriers). This plan has been twice successful with the A154 and A418 dikes construction.
2.1.7 Constraints
The construction work to be undertaken at the Diavik Diamond Mine must be carried out in such a manner as to minimize environmental impact. However, the overall project schedule, climatic conditions and the need to use large scale construction equipment places constraints on: the methods used; the rates of dredging and fill placement, the layout of the installations; and the positioning of turbidity barriers.
In addition, there are limits to the capacity for on-land storage of dredged sediments. Pond 3 has an available storage capacity of 1,000,000 m3 and the North Inlet storage facility has a total capacity of 2,100,000 m3.
The dredging activities, requiring the removal of approximately 110,000 m3 of dredged solids are anticipated to be completed in approximately 35-40 days.
Document#: CLSR-002-0513-R3 Page 6 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
The cut-off wall totals approximately 22,500 m2 over a length of 2.1 km. Construction is to be carried out in temperatures not less than -100C (jet grouting and curtain grouting excepted) but cannot begin until dredging and embankment placement are sufficiently far advanced to provide a working platform.
The main component of embankment fill placement will be completed in year 2016 with cut-off construction commencing in 2016 and to be completed in 2017.The dewatering of the A21 pool is scheduled to commence in the latter part of 2017 and complete in the first quarter of 2018.
From the inception of the project, DDMI, design engineers and contractors have worked together to develop a design for the water retention dikes which best suits the site conditions and conforms, to extents possible, to Best Management Practices (as described in Section 1.2). The design is proven based on the successful construction and performance of the A154 and A418 dikes.
Document#: CLSR-002-0513-R3 Page 7 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
3.0 OVERVIEW OF CONSTRUCTION SCOPE AND SCHEDULE
This section is intended to provide an overview of the construction scope and schedule that are related to the A21 Dike construction. The A21 construction is anticipated to start in 2015 and be completed in 2017 with finalization of initial pool dewatering in 2018. An approximate construction schedule is presented in Figure 3.1.
A summary of the construction scope and schedule is presented in Table 3.1:
Table 3.1: Construction Scope and Schedule Summary Year 2015 2016 2017 2018 ACTIVITIES Mob and set-up Mob and set-up Mobilization Dewatering Pads and laydowns Demobilization Demobilization Pre-strip Turbidity barrier (shallow) Turbidity barrier CSM Pre-drill Toe Berms Dredging (deep) COW (deep) Production Boulder removal CSM Calibration Thermosyphons Mining Filter Blanket Dredging Instrumentation Demobilization Embankment Placement Filter Blanket Jet Grout Vibrodensification Embankment Dewatering Placement Pipeline Vibrodensification Crushing Grout curtain CSM Pre-drill COW (shallow) Crushing
Document#: CLSR-002-0513-R3 Page 8 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 3.1: A21 Dike Construction Schedule
Document#: CLSR-002-0513-R3 Page 9 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
4.0 CONSTRUCTION PHASE ORGANIZATION AND RESPONSIBILITIES
4.1 Introduction The overall project organization is illustrated in Figure 4.1. The construction management scope of A21 dike will executed by a dedicated DDMI project team. To ensure timely response to environmental incidents and adequate reporting, the experience of the A154 and A418 dikes will be used to implement a communication system if any environmental incidents occur.
4.2 Overall Project Organization As per Figure 4.1, the overall project organization consists of the following parties:
• DDMI: Owner’s Team. The Owner’s team will include Project Manager, Construction Superintendents and Supervisors, Commercial Manager, Senior Project Engineer, Document Controller, Cost Engineer, Scheduler, Procurement/Contracts Manager, Administrative Assistant and Contract Administrator.
• BGC Engineering: Engineer – both on site and home office teams. BGC is the design engineer of record and will work with DDMI to ensure that all aspects of the environmental, contractual, and technical requirements are met. The quality assurance (QA) will be based on the continuous involvement of BGC and DDMI staff during the execution of all works included in the contract.
• Specialty Contractor: Specialty contractors will be retained for the dike foundation preparation (boulder/sediment removal and filter blanket placement) and cut-off wall construction. Specialty contractors will be responsible for mobilizing the required manpower, equipment and material to successfully execute the work included in the contract documents.
The overall organization is carried out in a partnering relationship between the three parties.
The Parties interact on a daily basis to ensure that standards are met regarding Safety, Environment, Technical and Contractual aspects of the work.
All parties participate in a weekly meeting to discuss of the various construction aspects and work progress.
Document#: CLSR-002-0513-R3 Page 10 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 4.1: Overall Project Organization
Document#: CLSR-002-0513-R3 Page 11 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
4.3 Responsibilities 4.3.1 DDMI
• Project Management:
a.) responsible for controlling and monitoring the project in terms of quality, cost and schedule, b.) development and implementation of QA, handover, commissioning, master schedule. c.) develop schedule and cost estimate, d.) procurement planning e.) preparation of all regulatory documents and work packages documents, assistance with tendering and the bid evaluation process for hiring the specialist contractor.
• Supervise and Manage Specialist Contractor:
a.) ensure coordination, collaboration and communication, b.) ensure Contractor has sufficient resources, undertake risk assessments, take an active leadership role in Health and Safety, c.) identify ways to improve efficiency of Works, d.) ensure quality of Works compliant with Federal or NWT requirements, e.) manage security deposits/performance guarantees/insurance, f.) receive/evaluate/recommendations for claims, evaluate invoices, g.) prepare progress claims, procurement and contract support.
4.3.2 BGC/DDMI
The BGC Contract will involve:
• Detailed Engineering:
a.) stamped report, drawings, technical specifications, b.) QA/QC manual, OMS manual, c.) permitting support. • Engineering and Home Office Support:
a.) periodic site visits by Design Manager and Project Engineer, b.) Design Manager on site for all critical stages (i.e. dewatering), c.) review of site technical reports, d.) review of supplier information, e.) reporting QA/QC, f.) technical advice to DDMI construction management team, g.) review of instrumentation data, h.) review of design changes suggested by DDMI, i.) drafting of design revisions, j.) complete As-Built reports which are primarily prepared on site by the Dike Engineer,
Document#: CLSR-002-0513-R3 Page 12 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
k.) continue support and presentation production for A21 GRB meeting(s).
4.3.3 Specialist Contractor/DDMI
The contract with a Specialist Contractor will involve:
• Supply of all management, supervision, administration, technical expertise, labour, equipment and materials, except Owner Supplied, to complete work scope aspects of the A21 Dike.
• Mob/demob of all equipment and material required by the Contract.
• Supervision, coordination and administration of Sub-Contractors.
Document#: CLSR-002-0513-R3 Page 13 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
5.0 CRUSHING FACILITIES
5.1 Crushing and Screening Operations The crushed materials used for construction of the A21 dike will be generated by the DDMI crusher.
The DDMI crusher is enclosed in a building and as such any potential dust emissions shall be contained within the facility.
The Diavik crusher was initially constructed for the purpose of reducing ROM material for transference into a Paste Plant that reduces the particle size further. The underground operation changed its mining method and as a result it no longer requires paste backfill, but instead requires a cemented rock backfill.
The crusher and back fill plant is a permanent facility and will be operated for the life of the underground mining activities.
The crusher is composed of the following components:
• A 48” wide Primary Vibrating Grizzly Feeder supplied by General Kinematics with an operating capacity of 350 mtph to 400 mtph and a nominal transport velocity of 40 fpm (12.2 m/min).
• From the grizzly feeder the material is fed into the Nordberg C160 Jaw Crusher and then transferred into the Terex Simplicity 5’ x 16’ Double Deck Screen, the oversize is then feed into the Nordberg GP300S Cone Crusher.
• Both the underflow from the screen and the material from the cone crusher will report to a conveyor that will stockpile the material outside the building.
The DDMI crusher is contained within a building with the exception of the crusher product conveyor. The dust inside the building will be extracted using a US Air Filtration Bag House that has 917 m2 of filtration area.
Document#: CLSR-002-0513-R3 Page 14 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Primary vibrating grizzly feeder:
The 48” wide Primary Vibrating Grizzly Feeder is supplied by General Kinematics for an operating capacity of 350mtph to 400mtph and a nominal transport velocity of 40 fpm (12.2 m/min) at the standard 5˚ inclination, carries an effective bed depth of 11” (280mm).
Primary jaw crusher:
The Nordberg C160 Jaw Crusher will be set to ≈ 180mm Closed Side Setting (CSS) preparing the secondary cone’s feed top size to fully utilize the selected crushers cavity profile. The feed to the cone will coincide with the upper gape of the cavity and thereby allow even wear of the liners down the chamber.
Secondary screen:
This Terex Simplicity 5’ x 16’ Double Deck Screen was initially configured for a 100mm top and 50mm bottom deck split. The 5’x16’ screen has the capacity to process a head feed of 600 mtph (≈86% load by screen area) depending on the particle size distribution and its capability to operate free of pegging.
Secondary crusher:
The Nordberg GP300S Cone Crusher equipped with an Extra Coarse cavity will crush the secondary screen covers at a setting of 45mm.
Document#: CLSR-002-0513-R3 Page 15 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
In order to produce the finer Zone 1 material there is a requirement to commission the tertiary crushers that were installed to produce feed for the paste plant but have never been used. On completion of commissioning, it is expected that the crusher will be capable of producing all but approximately 108,000t of Zone 1A material for which a small screening plant will be mobilised on the 2015 winter road.
5.2 Production and Schedule Crushing of Type 1 ROM material will be done using the existing DDMI crushing plant. It is planned that the crusher operates at its nominal design capacity (315 tph) to meet the crushing schedule. Type 1 ROM rock will be processed into several crushed, rock products of varying gradations for use as engineered embankment fill in the A21 Dike, laydown pads and site roads.
Zone 2 ‘Jaw run’ material crushing will commenced in early 2015. All crushing will be complete by December 2016
Crusher feed will be from the North Country Rock Pile and Dump 12. The DDMI mobile fleet will be used for re-mining and hauling of material to the crusher and from the crusher to the stockpile pads on South Island.
To ensure that the ROM material being fed into the crusher will be Type 1, visual geological inspections will be used during the re-mining operation for A21 as well as on site surveying, engineering design and record management. The Type 1 areas for re-mine have been identified by the mining engineers using mine design software. The boundary lines are provided to the surveyors who stake the limits on the dumps that are currently being re-mined or planned for re-mine in the near future. Conservative boundaries are used to help ensure that only Type 1 material is fed to the crusher.
5.3 Equipment The plant equipment will be maintained in good working condition as to ensure maximum production rates within the specified gradation requirements. The mobile screen unit is not enclosed and therefore will be outfitted with dust suppression guards, wet suppression water sprays and operated in a manner to minimize the production of deleterious quantities of airborne dust.
5.4 Stockpiling Stockpile sites will be firm, dry, reasonably level and free of all foreign materials. Before stockpiles are built level pads of Type I ROM will be constructed at each stockpiling location to prevent contamination of the granular materials. A minimum granular cover over tundra shall be maintained at all times. A plan showing the locations of processed materials, to be stockpiled on South Island, is presented in Figure 1.2. Run-of-mine Type I rock will come from the North Country Rock Pile and Dump 12.
Stockpiles will be monitored on a continuous basis for the following:
• To ensure that segregation during stockpiling is minimized.
• To ensure that snow and ice is not incorporated into the products.
Document#: CLSR-002-0513-R3 Page 16 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
• To ensure no organic matter, frozen lumps, ice, weeds, sod or roots are present in the stockpile.
• Monitor feed material to ensure it is free of organic matter and other unsuitable material.
When re-handling materials, stockpiles shall be built by dumping loads side by side until the complete area of the base is covered. This layer will be levelled and successive layers built in a similar manner completing each over the entire stockpile before beginning the next layer.
When removing aggregates from stockpiles, care will be taken not to contaminate the material with deleterious materials from the wheels or tracks of the loading tool.
The following practices will be observed for stockpile building:
• Stockpiles of different materials will be built far enough apart to prevent intermingling.
• Stockpiles will not be built in high conical piles. Stockpiles will not be built by dumping loads over end of bank.
• Size stockpiles to meet the project requirements while maintaining the smallest possible footprint.
• Dozers will not be used on stockpiles if segregation becomes apparent.
5.5 Quality Control Quality control for the crushing operation will be performed in accordance with CSA and ASTM methods, on a continuous basis.
Sources of samples may include:
• Samples taken from the crusher discharge.
• From stockpiles during their construction.
• At the location and time of loading delivery vehicles at the North Country Rock Pile and Dump 12.
• From the area of placement, after the material has been placed and spread but before compaction.
Sampling and testing will be conducted on each aggregate product to confirm that the grain size distributions are in accordance with the specifications. The test samples will be drawn from a sample point on a discharge belt or from stockpiles if necessary. Samples will not be taken from the bottom 600 mm of the stockpile.
Results of the tests will be submitted to the Project Engineer within 24 hours of the completion of the test. If the test results show the product to be out of specified gradation, the crushing and
Document#: CLSR-002-0513-R3 Page 17 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
screening operation will be immediately adjusted or stopped to repair damaged equipment, replace worn parts or make other adjustments to the operation.
5.6 Reporting A weekly report of the crushing and screening operations will be submitted to the Project Manager and will include the following:
• Aggregates processed and delivered to stockpiles, showing each category separately.
• A tonnage estimate of all materials produced based on scale readings, showing each category separately and the cumulative totals to date.
• Special items of note such as shortages.
A weekly report, submitted to the Project Manager, of the laboratory results summarizing weekly production, results of discrete gradation tests and an average gradation of each product type.
5.7 Engineering and Gradation Specifications Crushed and screened aggregates will be produced in accordance with Engineering Specifications.
The aggregates produced will be:
1. Zones 1A: 56 mm minus blended crushed rock. 2. Zones 1, 1B/1C: 50 mm minus crushed rock, higher fines content than Zone 1A. 3. Zone 2: 200 mm minus jaw run crushed rock.
Zone 3 which is a 900 mm minus product is not crushed: it is run of mine (ROM) rock. Some sorting is periodically required.
All aggregates are to be:
• Composed of inert, sound, hard, durable products of blasted or crushed rock, gravel, sand and fines capable of withstanding the deleterious effects of exposure to water, freeze-thaw, handling, spreading and compacting.
• Reasonably uniform in quality and free from soft, laminated or disintegrated particles.
• Free from organics, till and other deleterious substances.
• All products are derived from Type I ROM bedrock.
Sand shall be one or a blend of the following:
• Natural sand
• Manufactured sand
Document#: CLSR-002-0513-R3 Page 18 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
• Screenings produced in crushing of rock (boulders or gravel.)
Document#: CLSR-002-0513-R3 Page 19 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
6.0 BATCH PLANT
The Batch Plant is part of the DDMI operations infrastructure. The Batch Plant was an important component of Version 2.0 of the A21 Construction Environmental Management Plan (CEMP) as this plant was to be used to for plastic concrete production for the cut-off wall. With the change in construction method to cutter soils mixing (CSM) (see Section 10.0) the importance of this facility for dike construction is reduced to typical operational levels and no longer warrants specific inclusion in CEMP Version 3.0.
Document#: CLSR-002-0513-R3 Page 20 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
7.0 TURBIDITY BARRIERS
7.1 Overview Silt curtains will be used to limit the transport of sediments outside the work areas within Lac de Gras. A large body of water such as Lac de Gras develops current patterns driven by wind conditions. These are highly variable and current velocities and directions vary accordingly. It would be impossible to stop the currents prior to the construction of the dikes. Turbidity barriers have been employed on numerous dredging and in-water construction projects, including the A154 and A418 dikes construction. Their efficiency is rarely, if ever, 100%. The barrier can be pervious (silt screen) or impervious (silt curtain) according to whether the strategy is to filter the water or divert the sediment plume to the lower velocity areas at depth. The latter approach has to be adopted where currents are expected. The depth of the curtain has been chosen with regard to the intended mechanism and to the constraints inherent to the site. The curtain can only be deployed and maintained in ice free water.
Two seasons of dike construction require turbidity barriers; 2015 and 2016. In 2015 in-lake activities are limited to the dike abutment area and so will have a local turbidity barrier. In 2016 for the larger construction program the turbidity barrier will encircle the entire A21 dike area. Additional lengths of turbidity barrier will be available for local deployment to deal with specific problem areas. The design, deployment, and monitoring of the A21 turbidity barrier will adhere to BMP and incorporate lessons learned from the A154 and A418 dikes construction.
7.1.1 Design and installation
In still water, turbidity barriers are most effective when installed to within 0.5 m to 1 m of the lake bottom. Practical consideration may limit the depth in deeper water.
In moving water, the curtain acts as a downward deflector of the silt laden water. If the curtain is too deep the current will force it to swing upwards and therefore the effective depth will be diminished. The documents published by the Great Lakes National Program Office (US-EPA, 2000) advise against use of the turbidity barrier in deep water (>6.5 m) and/or in fast currents (>50 cm/sec).
In accordance with BMP, in order to place the most effective tools at the disposal of the project construction team and based upon the A154 and A418 dike construction project experience, it has been decided for 2016 to deploy a deep turbidity barrier, around the A21 dike, with means to shape the curtain to adapt the depth to topographic features, current conditions and to reduce damage during storm events.
The turbidity barrier will be made of Low Temperature Arctic, Coated PVC 22 oz LTA. The turbidity barrier is supplied in 15 m sections that will be attached together at the work site. It has a top load line and robust stress plates that can handle difficult sites where wind and current exposure are severe. Two anchors (inside and outside of the alignment) will be installed at designated intervals in order to properly stabilize the sections.
Figures 7.1 and 7.2 illustrate the desirable alignment in plan and in profile respectively. Figure 7.1 also shows the DDMI proposed monitoring stations A21-A, A21-B and A21-C The dredge swing cables require anchors to be positioned at least 40 m outside the dredge footprint to accommodate the angular movement of the cable and to permit at least 15 m of advance
Document#: CLSR-002-0513-R3 Page 21 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
before repositioning of the anchors is necessary. The turbidity barrier itself must be offset by a minimum of 100 m from the toe of the dredging cut to accommodate anchoring and working clearances required by the dredging operation. Clearance is essential between the line of the turbidity barrier anchors and those of the dredge to prevent entanglement during installation. (Figure 7.3).
The turbidity barrier will be deployed as near to the bottom as is practical to accommodate lake current flow while at the same time not allowing for re-suspension of lake bottom sediment (Figure 7.3). Note that the turbidity barrier sections near the shore (+/- 2 meter deep) will be resting on the bottom of the lake. This will prevent the suspended solids from going underneath the turbidity barrier due to wave effects at the shore line.
Different depths of panel will be used to cover the barrier vertical surface area as illustrated in the profile shown in Figure 7.2.
Figure 7.1: Turbidity Barrier Plan - 2016
Document#: CLSR-002-0513-R3 Page 22 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 7.2: Turbidity Barrier Profile - 2016
Figure 7.3: Turbidity Barrier Sections and Details - 2016
Document#: CLSR-002-0513-R3 Page 23 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
For 2015 the turbidity barrier alignment will encircle the in-lake construction area at the north dike abutment (Figure 7.4). The 2015 turbidity barrier alignment was selected to follow as closely as practical the 405m elevation contour to enable procurement of a single depth of material. The alignment also had to provide adequate distance from the construction activities such that marine equipment could navigate. This includes use of a deep area within the ultimate pit area for marine disposal of excavated foundation material (see Section 8.0).
Figure 7.4: Turbidity Barrier Plan – 2015
Document#: CLSR-002-0513-R3 Page 24 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
7.2 Deployment 7.2.1 Installation of End Anchors on Islands, Bottom Anchors and Buoys
End anchors and bottom anchors will be installed from the water using a barge and tug in the lake and a boom truck will be used for island mooring.
End anchors located on the abutments will be installed using drilling equipment such as pluggers or air-tracks, depending on the size and depth of anchors. End anchors could be frozen into the hole with water and sand or grouted.
Bottom anchors will be lowered with a portable winch from a barge and gently placed on the bed. Buoys will be attached to the anchors.
Installation of the turbidity barrier curtain will follow.
7.2.2 Turbidity Barrier Installation and Removal
Turbidity barriers will be used during the 2015 and 2016 construction season lakebed sediment removal (only in deeper sections of the dike) and the construction of the A21 embankment dike to elevation 419.0 m.
Following are the general turbidity barrier installation activities:
1. Platforms - Working platforms will be constructed on land near the points of entry in order to set up the system (unfurl, attach sections together and furl back).
2. Installation - When approximately 240 m lengths of curtain are connected together, the section will be pulled in the water using the tug boat’s tow line and taken into position, in between the bottom anchors. Two work boats will be used to attach and adjust the silt curtain.
3. Repairs - In case of damage, replacement sections of complete silt curtain system will be kept on site. When a section of curtain needs to be repaired, the damaged piece will be removed and replaced by a new one. The damaged one will be taken back to storage for repairs.
Progressive Removal - It may be that schedule restraints trigger the need for progressive removal of the turbidity barrier. If this is required the barrier can be broken into sections and pulled onto the newly constructed embankment. This progressive removal may reduce the mixing zone along the dike, as well as reduce the risk of damaging the barrier during removal as the lake ice is forming. In approximately early October the removal of the last section of barrier will commence in anticipation of the formation of ice. The removal will start at the southern tip of the peninsula where the lakeside embankment placement work will have been completed and will end in the area along the length of the dike where the last of the material has been placed in the lake.
Document#: CLSR-002-0513-R3 Page 25 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
7.2.3 Control
Turbidity barrier installation will be carried out by the Contractor under supervision of DDMI/BGC quality assurance teams. The position of the barrier will be controlled by GPS. Figure 7.1 and 7.4 illustrates the preferred alignment. Monitoring stations (A21-A, A21-B, A21- C.) for both 2015 and 2016 are shown on Figure 7.1 The dredge swing cables require anchors to be positioned at least 40 m outside the dredge footprint to accommodate the angular movement of the cable and permit at least 15 m of advance before repositioning of the anchors is necessary. Clearance is also required between the line of the turbidity barrier anchors and those of the dredge to prevent entanglement during installation (Figure 7.3).
Throughout the construction season the turbidity barrier will be inspected daily by the Contractor and after storms. If movement is suspected the position of the curtain will be checked by GPS. DDMI Environment will conduct daily visual inspections throughout the DDMI monitoring program.
Monitoring of the TSS and turbidity will be used to assess the effectiveness of the turbidity barrier and to determine requirement for any adjustments and/or additions.
7.2.4 Contingencies
Additional lengths of silt curtain will be available for deployment to address local problems or to install a parallel barrier in certain areas if necessary.
Document#: CLSR-002-0513-R3 Page 26 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
8.0 FOUNDATION PREPARATION
8.1 Introduction The footprint of the A21 dike contains boulders and areas with varying thicknesses of fine sediments. Boulders along the foundation can interfere with the cut-off wall construction and placement of the filter blanket. Lakebed sediment, if left in place in deep portions of the footprint, have the potential to generate high pore pressures on loading. In the shallows, these sediments are generally absent to any significant thickness.
Sediments in the deep portions of the footprint will be removed by dredging prior to the start of embankment construction. Dredging methods include both marine-based clam shelling and hydraulic dredging depending upon the location and year. The total quantity of sediment (including void space in situ) to be removed by dredging amounts to an estimated 110,00 m3. Figure 8.1 shows in the plan those areas of the dike foundation to be prepared via dredging, and those for which marine-based clamshell or land-based hoe excavation are planned for removal of boulders identified as unacceptable below the limits of the dike embankment.
8.2 Conventional excavation 8.2.1 Overview
This section will address the removal of the lakebed sediment and boulders by conventional excavation methods. In the near shore areas the fine particles have been washed from the parent glacial till leaving cobbles and boulders, such that in shallow water areas there are minimal to no sediments requiring removal. In deeper water the sands and silts have been deposited, and it is in these areas where hydraulic dredging will be undertaken.
The foundation preparation near the shoreline and in the shallows will therefore involve removal of boulders or sediment as required below the limits of the dike core and filter blanket zones and for this reason the operation will be carried out by backhoe. A marine based clamshell will be used in deeper areas unreachable by the hoe excavator. Anticipated boulder and sediment removal limits are shown in Figure 8.1.
Document#: CLSR-002-0513-R3 Page 27 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 8.1: Lakebed Foundation Preparation Plan
Anticipated sediment removal limits shown on left side of figure, with expected boulder removal limits shown on right side of figure. 8.2.2 Equipment
A 175T Manitowoc 4000W crawler crane will be mobilized to site on the 2015 winter road along with a 150T sectional barge and sectional split hull hopper barge. All of the conventional excavation work will be performed from the barge mounted crane using the hopper barge to transport excavated materials. This configuration can excavate to depths of 35 m.
Depending on the specific activity, the crane will be using either a conventional heavy duty digging bucket for sediment removal, to ensure adequate penetration into the sediment and to handle any rocks, or orange peel style grapple to perform the boulder removal.
8.2.3 Operating Procedures
The work will commence in 2015 and 2016 with the installation of the turbidity barrier or within an enclosure formed by a section of turbidity barrier installed for a smaller area cleared of ice ahead of the breakup.
The equipment will work primarily from a barge except at shorelines where water depths are insufficient.
Only experienced operators will be used to excavate the boulders and sediments while minimizing the re-suspension of sediments into the water column. Materials from the marine excavation will be loaded on to a slit hull hopper barge for transportation to and disposal on the open-pit footprint (see Figure 7.4). Dredged sediments tend to sink as a massive slug of material when the hopper barge is dumped thereby minimising the turbidity created. There is some mixing around the edges of the slug of solids, but much of this turbidity is drawn down by
Document#: CLSR-002-0513-R3 Page 28 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
the suction of the sinking solids. The turbidity that does result will be contained within the turbidity barriers.
8.2.4 Controls
The excavation site will be monitored for sediment re-suspension by DDMI. Appropriate measures will be taken to limit the extent of disturbance. It is anticipated that clamshell dredging will produce more suspended solids per unit volume than the hydraulic dredging and therefore this activity will be limited to times, areas and materials which cannot be handled by the hydraulic dredge.
8.2.5 Contingencies
If the primary turbidity barrier does not adequately control the sediment plume, then an additional silt curtain could be deployed to create specific enclosures around higher suspended solids generating activities.
8.3 Hydraulic Dredging 8.3.1 Overview
The hydraulic dredging operation within the A21 dike footprint will commence in early July 2016 and is scheduled to be completed by the end of August 2016. The operation entails the removal and transport of the lakebed sediments by hydraulic methods to storage on-land in Pond 3. Several types of dredge could conceivably be used to carry out this task, such as: • bucket ladder
• suction dredge
• cutter suction
• large submersible pumps
With due consideration for; lakebed topography, range and variability of sediment depths, disposal site distance and elevation, required production rates, environmental concerns and the experience gained during the A154 and A418 construction projects, the cutter suction dredge was chosen as the method most likely to fulfill the requirements and maintain the overall construction schedule.
Several references are available which include the evaluation of hydraulic dredge types and the relative potential to re-suspend sediments. Compared to other hydraulic dredge types, the cutter suction dredge produces relatively low concentrations of suspended sediment.
8.3.2 Installation
The hydraulic dredging work will be done with a newer model suction cutter dredge that will be mobilized to site on the 2016 winter road. It will consist of a suction pipe with a cutter mounted on the ladder and capable of cutting down to an elevation of approximately 398m (Figure 8.2).
Document#: CLSR-002-0513-R3 Page 29 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 8.2: 16-Inch Cutter Suction Dredge
Advancement of the dredge will be performed using one walking spud and one holding spud. The movement of the cutter head across the dike footprint to be dredged will be performed by the swinging action of the dredge around the walking spud (Figure 8.2). The dredge swing is controlled by swing wires secured with anchors to the lake bottom on both sides of the dredge, as illustrated on Figure 8.3.
Figure 8.3: 16-Inch Cutter Suction Dredge Layout Plan
Document#: CLSR-002-0513-R3 Page 30 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
For each dredge advance of 15 to 20 m the swing anchors will need to be moved to a new location.
A pump, installed on the ladder behind the cutter head feeds the slurry to the main pump on the dredge pontoon. Three booster pumps are installed on land in the pipeline transporting the slurry to the discharge point in Pond 3 (Figure 8.4). Most of the dredged solids are expected to settle out in Pond 3. Turbid water from Pond 3 will then be pumped to the North Inlet Pond (NI). The use of a ladder pump improves suction which enhances performance and reduces sediment re-suspension. The total estimated volume of dredge slurry to be pumped to Pond 3 is estimated to be 110,000 m3 of solids (including voids in situ within the lakebed).
Figure 8.4: Dredging Pipeline Alignments
Document#: CLSR-002-0513-R3 Page 31 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
The floating pipeline from the dredge to land is part steel pipe with floats and part HDPE with floats. The discharge pipeline in Pond 3 will be fixed to a float tethered to shore to allow relocation of the discharge point as necessary.
a) Anchor design – The selection of the anchors is based on the ability to penetrate through sediments with minimal displacement and secure anchoring to the lake bottom. Danforth-type anchors with sharp fluke points have been selected (Figure 8.5).
Figure 8.5: Danforth Anchor Used for Dredge
b) Underwater video camera– An underwater video camera will be installed directly on the ladder at above the cutter. This will provide a direct visual control of turbidity around the cutter. The set up will include a light source.
c) Turbidity testing equipment – A turbidity meter will be installed on the ladder for direct measurement of turbidity close to the cutter. The meter will be installed within the field of vision of the video camera. This will permit a correlation of the visual observations to the quantity of suspended sediment.
d) Biodegradable Canola based oils can be used down to –10°C. Oil tank heating will therefore be necessary for cold starts but the oil stays hot during the operation.
8.3.3 Operating Procedures
It is acknowledged that the skill and experience of the dredge operator (leverman) has the greatest influence on the amount of sediments re-suspended in the water. Only highly experienced personnel will be used. The leverman has a number of input parameters at his disposal (Figure 8.6) and equally several different actions to be taken, many of which are interrelated. The parameters include:
Document#: CLSR-002-0513-R3 Page 32 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
• swing wire tension
• swing speed
• GPS screen for cutterhead location
• vacuum in the suction line
• pressure in the discharge line
• pipeline slurry velocity
• hydraulic pressure and rotation speed of the cutterhead
• torque on the cutterhead
Document#: CLSR-002-0513-R3 Page 33 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 8.6: Typical Dredge Control Room
The operation will start by pumping clean water (cutter off the bottom) through the whole system to establish baseline readings for the instruments.
The following operating procedures will be adopted to minimize TSS loads:
a) Cutter speed - Cutter speed will be reduced to a minimal setting for optimal production rate. For example, where the sediment thickness requires two cuts, the upper cut in the less consolidated material will be done with a slower cutter speed than the lower cut.
b) Dredge swing speed – The speed of lateral movement will be controlled by variable speed winches. This speed will be set up so as not to disturb more of the lake sediments than can be readily removed by suction and it will be correlated to cutter speed.
c) Suction - Vacuum suction will be controlled by regulating the ladder pump speed.
d) Velocity meter – With increasing slurry density, the pump power has to be increased to ensure the pipeline velocity is adequate to limit solids settling out in the pipeline.
Document#: CLSR-002-0513-R3 Page 34 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
e) Ladder hoisting – This is a common dredging method in soft sediments that allows the ladder to be lowered to the bottom of the cut so that the solids can fall naturally on top of the cutter and be removed efficiently by suction pipe. On this site, it is intended to use a different method that should minimize turbidity and residual fluff falling behind the cutter. The sediments will be removed in horizontal layers of approx. 1.0 m in height (adjusted to the size of the cutter of 1.1 m dia.), from top to bottom, which mitigates disturbance. This will mean that the dredge must make two or more sweeps across the dike footprint before advancing. The hoisting of the ladder is controlled by variable speed winch. The ladder position will be measured by GPS, and by an air pressure meter for water depth.
f) Fluff removal – The dredge will return to do a second cleanup pass over each sector to reduce the residual sediment to the specified maximum. This is necessary both for dike stability and to reduce sediment re-suspension during fill placement.
g) Spud and anchor setting and lifting – Since all winches have variable speed controls, optimal speeds to operate both spuds and all anchors will be employed to minimize turbidity. Note that the spuds and anchors will be lowered rather than dropped.
h) Pipeline draining – Periodically it will be necessary to add or remove sections of the floating pipeline. The pumps are run to fill the line with clean water prior to breaking the line. The break will be made in deep water to minimize scour caused by water emptying from the line. In addition check valves minimize the quantity of water released.
8.3.4 Controls
The DDMI environment personnel will be responsible for monitoring the sediment plume and will feed data to the dredge operators to permit adjustments to be made as necessary.
The extent and frequency of testing (TSS and turbidity measurements) will be determined during the initial phases of construction and will be greater at the beginning with some reduction as warranted with the experience gained. The compilation and analysis of this data will constitute an ongoing activity in the management of the construction activities.
8.3.5 Contingencies
Dredging operations will be shut down in severe weather conditions, i.e. storms, high winds, etc. if the leverman notes that waves are causing difficulty with cutterhead control or stress to the ladder, swing wires and anchors. Each shut down will entail filling the discharge lines with clear water to avoid having solids settle out in the line or the discharge of sediment in the event of a break.
The on-land discharge lines will be under constant surveillance. Line breaks are a low probability but the surveillance and the monitoring of pressures by the leverman will permit prompt identification of a problem and shut down.
The dredge and fuel scows will carry oil spill kits and personnel will be trained in their use. The kits will consist of an inshore boom made of PVC coated nylon fabric and closed cell polyurethane floatation cells with chain connectors.
Document#: CLSR-002-0513-R3 Page 35 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
8.4 Environmental issues Because of the depth of the lake, (up to 25 meters maximum along the A21 dike alignment) the thickness of the soft sediments (1 to 5.5 meters), required production rates and the A154 and A418 experience, it is proposed to use a conventional cutter/suction dredge to remove the soft lake-bottom sediments where possible. It is estimated that the dredging action may cause up to 20% of the sediment being dredged to be placed into suspension and create a dispersion plume as the sediments are transported and re-deposited down current of the source. The increase in the suspended solids can affect fish and spawning grounds in the path of the plume if the TSS rises above tolerable levels. Maximum exposure duration criteria for the protection of fish, applicable 200 meters from the dike, are shown in Table 8.1, Target TSS Concentrations for Protection of adult and juvenile fish.
Table 8.1: Target TSS Concentrations for Protection of Adult and Juvenile Fish Duration of Exposure Target TSS (Days) (mg/l)
0.1 45228 0.5 9273 1 4686 2 2368 3 1589 4 1197 5 961 6 803 7 690 8 605 9 539 10 486 15 326 20 245 25 197 30 165 35 141 40 124 50 100 60 83 70 71 80 63 90 56 100 50
**Note: Exposure duration criteria within 200 m of the Dike.
Available TSS and turbidity measurements of the A154 and A418 dike do indicate that at least 95% of the sediments put into suspension will settle out of suspension in two hours during dredging. Because the rate of settlement of the disturbed sediment is fast, most of the
Document#: CLSR-002-0513-R3 Page 36 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
re-deposition will be close to the source and cumulative effects are not expected to exceed the exposure criteria.
Other potential environmental issues are related to accidental spills or equipment failures such as:
• leaking or broken dredge discharge lines
• spills of fuel, oil or other materials from the dredge into the lake
• accidental slippage of a tool or container of hazardous materials into the lake
• operational noises
8.5 Management Measures A number of environmental management measures will be implemented to protect the lake environment during the dike construction. The measures are as follows:
• The dredging activity is not expected to create turbidity exceeding the exposure criteria in Table 8.1. Dike construction activities will be carefully monitored, as described in Section 8.5.1. To determine the effects of the dredging operations, the quality of the water at various distances from the initial dike construction site will be monitored before, during and after construction.
• If accidental breakage, spills or leaks occur in the sediments discharge lines, the dredging operations will be stopped until the defect is repaired. During line pressurization, some water/sediment will escape from the ball joints along the estimated three or four sections of flexible steel pipeline. Once the system is pressurized, the ball joints tighten preventing uncontrolled discharge of dredge slurry.
• When refueling the dredge, an oil spill containment boom will be temporarily deployed in a circle completely surrounding the dredge. If a spill occurs, it will be contained and cleaned up with absorbent pads.
• Spills of fuel or lubricants on land will be cleaned up using absorbent pads and contaminated soil disposed of in accordance with the Emergency Response Plan, which forms part of this Water License Application.
• Spills of fuel or lubricants on the lake surface will be cleaned up and reported in accordance with the action plans specified in the Emergency Response Plan. Booms will be used to contain the oil slick, and absorbents, skimmers or vacuum equipment used to clean up the surface. The dredge contractor will be required to provide enough oil spill containment booms on board at all times for encircling the dredge.
• No disposal of garbage or material in the lake will be allowed. Personnel will be required to transport all waste back to shore for incineration or disposal in the appropriate area of the waste disposal facility, or storage prior to removing from site.
Document#: CLSR-002-0513-R3 Page 37 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
• At certain times, divers will be on duty to carry out visual inspection of the lakebed, evaluate the efficiency of the dredging operations and collect soil samples for laboratory testing and foundation approval. Also, retrieval of tools or equipment that accidentally fall into the lake may be attempted by the divers with due caution and reference to the Emergency Response Plan.
• All engines to be used in the dredging operations must be in sound mechanical condition and will be equipped with effective exhaust systems to minimize disturbance to wildlife.
8.5.1 Monitoring and Controls
Trained and qualified DDMI environmental personnel will monitor turbidity in the water column adjacent to the dredging operations and beyond. Profiling measurements will be made using multi-parameter instruments, which include temperature, conductivity, turbidity, and pH. A computerized data acquisition system will be integrated to provide real-time data acquisition and documentation and to control dredging rates and head manoeuvring.
The monitoring data will be used to manage the dredging operations and specific decisions will follow the decision-making flowchart used for the A154 and A418 dredging operations, as shown in Figure 13.2 and discussed in Section 13.1.1.
The water quality readings will be monitored by DDMI’s Environmental Department who will also periodically retrieve representative samples of the water column in the vicinity of the dredging operations for laboratory testing for correlation, control and calibration of the field monitoring devices.
The dredging contractor will routinely inspect the pipelines and floating discharge lines to ensure that no observable defects exist. Daily reports will be filed documenting the progress of the work, areas of concern, equipment condition, monitoring results including anomalies and other observations. DDMI will conduct weekly audits of the floating discharge line, on land transfer line, booster stations, and the discharge point. Any non-conformance items will be addressed with the dredging contractor.
8.6 Drainage and Piping Pumps on the dredge will transfer the sediment laden slurry (estimated to contain 7.5 to 20% solids by weight) to an on-land discharge point located at Pond 3 (see Figure 8.4) via a floating pipeline, connecting to a land pipeline. The discharged solids will be retained in Pond 3. Turbid water from Pond 3 will then be pumped to the North Inlet for treatment and discharge to Lac de Gras.
The dredged sediments from Pond 3 can be available, if required, as potential reclamation materials in the future.
The pipeline will be laid on the surface of a prepared pipe bench adjacent to existing roads. The pipeline will be protected by corrugated steel pipe where it crosses roadways.
Document#: CLSR-002-0513-R3 Page 38 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
9.0 A21 DIKE EMBANKMENT PLACEMENT
9.1 Overview The A21 water retention dike will be constructed from Type I ROM rock and Type I crushed rock. Embankment design is based on transitioning filter compatible fill zones along the section. Three types of material have been specified (based on grain size distribution) to fulfill the design requirements of filter criteria, slope stability and limit deformation. The filter blanket will be placed directly on the dredged lake bed and the remaining materials pushed into the water from the advancing face. Refer to Figure 9.1 for a general, simplified cross section.
Figure 9.1: Typical Dike Design Section
A154 and A418 dike provide precedent at the mine site for construction by the slip-displacement method (i.e. placing fill into water). This experience demonstrated that some of the fines within Zone 1 material may be washed by currents and waves and briefly go into suspension. However, these fine particles settle out rapidly within the enclosed working area.
9.2 Construction Methods • Filter blanket – Zones 1A/1C
Filter blanket will be placed via the barge mounted crane equipped with a clamshell bucket. The clamshell bucket will pick up the material filter material from hopper barge and lower it to the bottom before releasing. This will not only reduce segregation but also minimize the generation of suspended solid. GPS is employed to control accuracy of placement and ensure the filter is contiguous.
Document#: CLSR-002-0513-R3 Page 39 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
• Embankment materials Zones 1/1B, 2 and 3
Haul tricks trucks will deliver materials to the embankment and bulldozers will place the bulk of the embankment material by the slip displacement method, which again is chosen to avoid segregation and the generation of suspended solids.
• Vibrodensification
The central zone of the embankment (Zones 1/1B) will be densified to improve stability, decrease the permeability of the central zone and, to reduce deformations during dewatering. Water is used to assist the initial penetration of the vibroprobe into the crest of the dike and is contained within the Zone 1/1B material and surrounding materials.
Table 9.1 summarizes the efforts to be employed to reduce suspended solids during embankment construction.
Table 9.1: TSS Minimization Methods during Embankment Construction Operations Component Methods to minimize TSS Aggregate Truck transport Water roadways for dust control transport Clamshell placement of Zone Clamshell Clamshell lowered to bed before opening 1A/1C Maintain dumping area away from working face of the Zone 1/1B, 2, and Aggregate transport dike. No end dumping directly into water will be 3 placement permitted. Extended length blade arm on dozer. Use of slip Fill push Aggregate placement displacement method.
9.3 Controls The Contractor’s quality control and the DDMI /BGC quality assurance teams will provide continuous monitoring of the suspended solids generated during this phase of the work. They will also be responsible for testing and inspection for the control of the material quality and resulting embankment.
The frequency of testing will meet or exceed the regulatory frequency.
As mentioned earlier, the crushed rock will have a small fines content. The placement methods will ensure that most of this fraction remains within the fill mass and not free to travel into suspension. Only the outer surface of the displaced load will be exposed to washing from the wave action induced by the movement of the material and dispersion. If necessary, stopping the work in high wave conditions will be one method of mitigating the amount of suspended solids.
All operating personnel and construction foremen are authorized and required to modify field operations in order to comply with environmental project standards for the Diavik project. This
Document#: CLSR-002-0513-R3 Page 40 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
will either be initiated by direct observation of the field personnel, or as test results are reported to them by Project Quality Control personnel.
A log of all reported incidents and responses will be maintained by the project Quality Control manager and distributed to DDMI Environmental. After an incident is reported, follow-up observations will be performed to verify the effectiveness of the response. Subsequent action may be required until specified project compliance is met.
9.4 Environmental Issues Construction of the A21 dike occurs predominantly under water and fill is pushed from the crest into water up to 25 meters deep. As the rockfill is placed under water, turbidity is created due to dust coating on the rockfill being washed off during placement. The turbidity created can become a threat to fish and their spawning grounds if the exposure duration criteria presented in Table 8.1 are exceeded.
Other potential environmental impacts from the dike construction are as follows:
• Dike construction will require the use of a fleet of heavy earthmoving equipment including front-end loaders, 100 tonne rock trucks, bulldozers, excavators, hydraulic grabs and compactors. This equipment will be diesel powered so there will be some risk of hydrocarbon spills.
• Hauling and placing operations will create fugitive dust emissions, which will have to be controlled.
• Noise and diesel fumes will result from the intense activities.
• Generation of sewage in the construction area from toilet facilities and lunch rooms.
• Interaction with wildlife on haul roads or in construction areas.
9.4.1 Management Measures
Measures that will be taken to manage the issues listed above are as follows:
• Prior to end dumping, soft sediment will be removed in the deeper portions of the dike footprint thereby exposing relatively dense lakebed till. Although done primarily to enhance the structural long term stability of the dike, removal of the soft sediment has the added environmental benefit of reducing the potential for turbidity during the fill placing operations. Since the till is coarser in composition and possesses a lower silt and clay content than the soft lakebed sediments, based on Stokes’ Law, any disturbed particles will on average settle out faster. In addition, less clay is available to disperse in a colloidal fashion. The A154 and A418 experience did show that the induced turbidity caused by the end-dumping operations is very low compared to that caused during the filter blanket placement.
Document#: CLSR-002-0513-R3 Page 41 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
• The water column in the vicinity of the end-dumping operations will be monitored by DDMI environment personnel to determine the turbidity. Turbidity barriers will be installed to retain the suspended sediments.
• Tracked equipment will be fuelled on the dike while wheeled equipment will generally be fuelled on the lakeshore.
• Spills of diesel fuel, oil, grease or other hydrocarbons will be cleaned up immediately, and in accordance with the action plans specified in the “Emergency Response Plan”.
• No garbage or refuse disposal will be allowed in the construction area. Personnel will be required to transport all wastes back to camp for incineration or disposal in the appropriate area of the waste disposal facility as stipulated in DDMI Waste Management system.
• Chemical toilets will be placed in the construction areas in accordance with the Northwest Territories Mine Health and Safety Regulations. These toilets shall be cleaned and recharged at least twice per week.
• All diesel-powered equipment shall be in sound working condition and must be equipped with mufflers to minimize acoustic disturbance to the wildlife. The contractor will be able to show documented evidence that the maintenance schedules are being maintained.
• DDMI shall be responsible for maintenance of the haul roads. Dust generation shall be controlled by spraying with water.
• All personnel shall receive Environmental Awareness Training as outlined in Appendix A. This includes instructions on how to appropriately deal with wildlife encounters. Drivers shall be instructed to slow down or stop when wildlife advisories are in effect and to report sightings to the Manager’s Representative (See also Technical Procedure No. 10.1-1 Traffic Management Procedure in Diavik Procedures).
9.4.2 Monitoring and Controls
The process used for monitoring and control of the effects of end-dumping operations on the aquatic environment will be the same as for the dredging operations. DDMI environment personnel will use a multi-parameter probe meter to make real-time measurements of the turbidity. Results will be used to optimize placing rates and methods.
The water quality readings will be evaluated by the Construction Manager. Should unacceptable quality persist, installing a second silt curtain may be considered. A second curtain installation was not required during construction of the previous two dikes.
DDMI environment personnel will also ensure routine inspection of the roads and construction area to ensure that no undue damage is being done to the environment. Weekly Reports will be filed documenting the progress of the work areas of concern, equipment condition, anomalies, and monitoring.
Document#: CLSR-002-0513-R3 Page 42 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
10.0 CUT OFF WALL - CONSTRUCTION
10.1 Overview Approximately 2.0 km of cut-off wall will be constructed through the embankment for the purpose of water seepage control. The cut-off wall will be constructed applying a method known as cutter soils mixing (CSM). This is different technology that used with the A154 and A418 dike construction that provide numerous benefits including environmental and safety with a proven performance record.
The CSM technique involves two basic steps:
1. Pre-drill and backfill. Along the dike centerline, overlapping large diameter holes are drilled through the dike embankment and 3m into the lakebed till. The holes are then backfilled with a 12.5 mm minus crush material (see Figure 10.1).
Figure 10.1: Typical CSM Pre-drill and backfilling.
Document#: CLSR-002-0513-R3 Page 43 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
2. Construct the plastic concrete cut-off wall through the backfill material using a series of overlapping CSM panels. CSM is a technology that construct panels of plastic concrete using a cutter-head to inject and mix cement/bentonite into the placed backfill crush (see Figure 10.2).
Figure 10.2: CSM equipment and operations.
Document#: CLSR-002-0513-R3 Page 44 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
10.2 Equipment Installations The equipment used to construct the cut-off wall are shown in Figures 10.1 and 10.2. Unlike the open trenching cut-off wall construction method applied for A154 and A418, the CSM method does not require large bentonite mix plants with ponds. Smaller slurry mix plants will be used to prepare the cement/bentonite/water product for CSM (See Figure 10.2) with locations strategically placed for each phase of CSM construction (see Figure 10.3).
Figure 10.2: Location of CSM mix plants for A21operations
The width of the dike crest is governed largely by the space required for these operations, along with equipment traffic and safety requirements. CSM equipment is more confined than conventional trenching methods, reducing safety concerns with traffic and congested areas. Within this constraint the dike was designed to require the minimum footprint and hence the minimum quantity of sediments to be dredged and embankment material to be placed.
Document#: CLSR-002-0513-R3 Page 45 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
10.3 Operating procedures The CSM operations reduces the potential for sediment discharge to Lac de Gras relative to conventional trenching cut-off wall methods by eliminating the need for cement-bentonite mix ponds and reducing the size/length of slurry pipelines.
Nevertheless, the potential for the discharge of material to the lake does exist and needs to be minimised by the construction procedures. The following is a summary of potential operating conditions that could result in a discharge and of the means to control this.
• Release from the slurry production or delivery;
• Accidental spillage or runoff from CSM area.
Table 10.1 itemizes the potential scenarios and presents the features built into the system or the measures to be taken to control discharges.
Table 10.1: CSM Wall Construction Issue Mitigation Options Potential Construction Sediment Defence Mitigation Sequence Discharge Source Slurry transport Break in pipeline Pipelines located between berms Availability of silt curtains pipeline near centre of dike working platform for local deployment. to reduce accidental damage and to contain leak. Vacuum trucks and pumps will also be Pipeline pressures will be monitored available to remove to detect leaks. spilled material. CSM Panel Slurry loss Slurry immediately mixed with Rate of injection can be (general) through fill or aggregate – limited free slurry liquid. modified. foundation. Dike cross-section provides for increasing width of central zone with depth.
Gradation of central zone chosen to minimise segregation.
The procedures described above will only be effective if all operations are carried out by well trained operators with experienced staff from the specialist supplier/sub-contractor overseeing the operation. Key DDMI personnel who were involved during the construction of the previous two dikes will oversee the various COW construction activities to ensure BMP are employed through-out the construction of the A21 dike.
Document#: CLSR-002-0513-R3 Page 46 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
10.4 Contingencies The contingencies are covered in the mitigation column of the table above. The spill response procedure is covered in a detailed directive presented in Section 15 – Spill Response On Land and In Lac de Gras.
10.5 Environmental Issues Potential impacts during the cut-off wall construction operations are as follows:
• Spilled cement/bentonite slurry could runoff into the lake resulting in increased turbidity.
• Minor dust releases when mixing bentonite or cement.
• Equipment oil spills can be deposited on the ground or in the water.
10.5.1 Management Measures
In order to minimize potential impacts on the environment caused by construction of the cut-off wall, the following measures will be implemented:
• Fluids will be kept central along the dike alignment with surface grades to limit potential for runoff.
• Powdery grout or slurry additives will not be poured from a height to minimize fugitive dust releases or fluid splatter.
• During all dike construction activities, the dike contractor will be required to keep an emergency supply of silt curtains close by for rapid deployment if excessive turbidity is being created in the vicinity of the works.
10.5.2 Monitoring and Controls
During the startup of the cut-off wall construction the water column in the vicinity of the dike will be monitored for turbidity and pH using a multi-parameter probe. Once it is verified that no significant adverse effects are being generated, the monitoring intensity can be reduced.
Environmental personnel will obtain random samples of the lake water in the vicinity of the cut- off wall construction operations for laboratory testing to ensure that the water quality is being maintained to an acceptable standard.
Document#: CLSR-002-0513-R3 Page 47 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
11.0 GROUTING EXECUTION
11.1 Overview Two types of grouting will be used in construction of the cut-off barrier;
• Jet grouting, and
• Curtain grouting
11.2 Jet grouting 11.2.1 Method
Approximately 1.7 km of jet grouted wall will be installed in 2017. The jet grout wall connects the bottom of the cut-off wall and the top of treated bedrock. This provides the dike with a contiguous water tight core firmly cemented to bedrock.
In summary, the jet grout method consists of the following steps:
• Drilling a row of closely spaced (typically 0.75 m) boreholes through the plastic concrete wall and the deep till foundation using rotary drilling techniques.
• A high-pressure horizontal water jet emanating from a nozzle near the base of the rotating rods is then used to remove the joint infilling in the rock formation, mobilize unconsolidated soil particles into a suspension and, to erode the fine particles in the deep till foundation. The drill string is slowly rotated as it is raised within the borehole.
• Additionally, pressurized air may be applied in the same manner as water. This will function to increase the radius of influence of the pressurized water by creating a reduced viscosity shroud (in terms of the kinematic and dynamic viscosity) within the region of the column being formed. This method is termed “three phase jet grouting”.
• The eroded soil is replaced by a high pressure cement–bentonite grout which may be the cutting medium or injected separately through an additional nozzle located below the first.
• The injection will be continued up to a minimum of 0.5 m within the plastic concrete to produce a sufficient overlap. Refer to Figure 11.1 for an illustration of the jet grouting method.
Document#: CLSR-002-0513-R3 Page 48 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 11.1: Jet Grouting Working Procedure
There is precedent for the use of jet grouting in sealing the foundation of new construction and in the rehabilitation of dams. On site the A154 and A418 dikes were constructed with jet grout columns which have functioned as predicted. With respect to controlling the return slurry as described below, the jet grouting method has not been found to be environmentally problematic. It was developed to eliminate the pollution potential of chemical grouting in the treatment of fine soils.
11.2.2 Execution
The operation requires:
1. setting up of handling facilities for the cement and bentonite, 2. batching and pumping plants, 3. delivery lines for the grout and for drilling water, 4. drill rigs and grout rigs, 5. a slurry return recovery system, and 6. survey layout of holes and drill mast alignment.
Document#: CLSR-002-0513-R3 Page 49 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Due to head loss in the delivery lines and to minimize wastage, the delivery lines are kept to a maximum length of 500 – 600 m for jet grouting. The drill rigs are equipped to record and provide the operator real time computer graphic monitoring of air/water/grout pressures, feed rates, rotation rate and, drilling advance rates.
11.2.3 Operation procedures
The jet grout operation will commence with drilling holes through the plastic concrete, the deep till foundation and penetrating about 1.5 m into bedrock. The drilling fluid and part of the slurry pumped to the jets will return to the surface with the cuttings. This return slurry is collected from close to the hole collar in the trench. Note that the backfill plastic concrete in the previous operation is kept below the top of the guide walls specifically for this purpose. From this point the slurry will be pumped to a tanker truck for transport to the disposal area, likely the area of Pond 12, which will ultimately be covered by a till stockpile.
The operation of the mixing plants is automated and the drill rig operators remotely control the pumps. This set up minimizes the possibility of overflow and permits rapid response in the event of a break in the lines.
The top of the dike will be graded such that any spill on the dike working platform will flow towards the trench rather than to the lake or the pool (i.e. reverse camber).
11.2.4 Controls
The operation, being specialized, will be undertaken only by experienced operators working under the supervision of the sub-contractors senior site personnel.
The quality control team will routinely test the fresh and in-situ grout. The DDMI, BGC and Contractor’s quality assurance teams will also observe the operation and ensure the appropriate measures are being taken to minimize spills and to remove materials promptly from the work platform to avoid leakage to the lake.
11.2.5 Contingencies
The contingency plan for a grout spill in Lac de Gras includes the deployment of silt curtain to limit the extent of contamination. A detailed spill response procedure is provided in Section 15.
Construction of the previous two dikes did not result in the introduction of any fluids from jet grouting operations into the lake.
11.3 Curtain Grouting 11.3.1 Methodology
Curtain grouting is used to reduce the permeability of the bedrock foundation of the dam to a nominal depth of 15 to 20 meters below the bedrock surface as follows:
• An optimized grout hole orientation is selected by analysis of bedrock structural mapping measurements using stereonet analysis. Hole orientations are selected, as much as possible, to be at right angles to controlling structure sets.
Document#: CLSR-002-0513-R3 Page 50 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
• Holes are drilled in a single line according to the spilt-spaced methodology. Primary holes are completed typically at 6 meter spacing. In between the primary holes additional holes are completed (secondary holes) and so on (tertiary, quaternary, etc.) until the subsequent holes meet closure criteria (based on either grout takes or water pressure test results).
• A pneumatic rubber packer is lowered and inflated to isolate portions (stages) of the open drill hole.
• A cementicious based grout mix is then introduced to the isolated stage through an opening in the end of the packer.
• Pressure, flow and penetrability of the grout mix are monitored in real time graphic format by the pump operator. Injection will cease based on reaching a pressure or volume limit.
Approximately 24 km of grout hole drilling is estimated for A21 Dike foundation treatment. This activity is scheduled to be completed in 2016.
11.3.2 Installation
During the course of curtain grouting, the viscosity and specific gravity of the cement-based grout mix is adjusted according to the ground-to-grout response (i.e. rate of absorption and volume injected) Circulation (delivery and return) lines are limited to around 100 m to minimize wastage during cleaning or removal of expired mixes. This requires that the grout plants must be portable and will be set up at various points along the dike. The drill rigs are equipped to provide and record data pertaining to the pressures, feed rates, drill flush return and drilling advance rates.
11.3.3 Operating procedures
The pressure grouting will precede cut off wall activities and jet grouting. The activity will commence with holes being drilled to the prescribed depth. Water will be used as a drilling medium.
The pressure grouting operation involves the use of a re-circulating pipeline system to keep the grout well mixed even during periods of low grout take. There is significant grout volume return to the surface as is the case for the jet grouting. The mix adjustment is made to ensure satisfactory sealing of the fissures in the rock but only within a confined area. Use of too thin a mix would result in the migration of grout beyond the area of interest and with the potential for leakage to the lake bed. Continuous observation of pressures and rate of grout take is required to make the appropriate adjustments. Again highly experienced personnel are critical for the efficiency and effectiveness of this program.
11.4 Controls The operation, being specialized, will be undertaken only by experienced operators working under the supervision of the sub contractors senior site personnel.
Document#: CLSR-002-0513-R3 Page 51 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
The Contractor’s quality control team and the DDMI-BGC quality assurance team will observe the operation and ensure that the appropriate measures are taken to minimize spill and to remove materials promptly from the work platform to avoid leakage to the lake.
Technical direction to the grouting sub-contractor will be given by DDMI (Project Managers) and BGC (Dike Engineer).
11.5 Contingencies The contingency measure for a grout spill in Lac de Gras will be the deployment of silt curtain to limit the extent of the contamination and suspension of grouting activities. A detailed spill response procedure is provided in Section 15.
11.6 Environmental Issues Potential environmental impacts during the grouting operations are as follows:
• Return water from drilling, loaded with drill cuttings, drilling mud and other additives could be discharged on the surface and flow into the lake thus creating some turbidity or local change in water chemistry.
• Return grout solutions can be discharged on the surface and flow into the lake.
• Grout from borehole injection can be discharged into the lake through interconnecting discontinuities in the bedrock.
• Equipment oil spills can be deposited on the ground or in the water.
11.6.1 Management Measures
The central part of the dike along which the drilling and grouting will take place consists of crushed stone fill that is relatively pervious. Grout fluids percolating into this medium will be filtered as they migrate towards the lake. Grout fluids discharged on the surface will likely percolate into the fill unless the surface of the dike is frozen. Grout communicating with the bedrock surface will be blanketed and filtered by the till layer which overlies the bedrock. Direct communication with the lake is unlikely.
DDMI will ensure that the grouting contractor has the capability to rapidly contain surplus grout flow to avoid the possibility of it entering the open lake.
Use of chemical additives to the grouting solutions will be avoided. No chemical accelerators, water reducing agents or chemical grouts will be allowed without the approval of the Construction Manager.
11.6.2 Monitoring and Controls
During the startup of the grouting activities the water column in the vicinity of the dike will be monitored for turbidity, conductivity and pH. Once it is verified that no significant adverse effects are being generated, the monitoring intensity may be reduced.
Document#: CLSR-002-0513-R3 Page 52 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
DDMI Environmental department will obtain random samples of the lake water in the vicinity of the grouting operations to ensure that the water quality is being maintained to an acceptable standard. Samples will be analyzed at an independent laboratory for correlation with the multi- parameter probe.
Document#: CLSR-002-0513-R3 Page 53 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
12.0 FISH SALVAGE
12.1 A21 Fish Salvage Program The objective of the fish salvage program is to transfer, live, as many fish as possible from behind the A21 dike and release them into Lac de Gras. The program is a requirement of DDMI’s Fisheries Authorization. The following program is generally the same as was used successfully for the A154 and A418 fish salvage but with consideration of more recent guidance from DFO:
Tyson, J.D., W.M. Tonn, S.Boss and B.W. Hanna. 2011. General Fish-out Protocol for Lakes and Impoundments in the Northwest Territories and Nunavut. Canadian technical Report of Fisheries and Aquatic Sciences 2935.
The field work will commence when the lake becomes ice free (roughly July 1, 2017) and continue until either the program is complete (see below) or field conditions are deemed unsafe by DDMI Site Safety Manager. A designated Project Biologist will be responsible for program integrity, data quality, direction of field crews, daily reporting to DDMI, participation in discussions with the Department of Fisheries and Oceans (DFO), and preparation of final report.
Three crews of 2 people per boat will conduct the salvage program. Local communities will be the preferred source of field crews. Crews will use fishing gear and gear types to maximize live fish salvage. Gill net sets will be restricted and standardized at 60 minutes and the timing of netting to be staggered during program to allow inclusion of early morning and evening periods.
Gear will include:
a) Gill nets – stretch mess size of 1 1/2”and 3 1/2”. b) Small sized trap nets. Once selected the gear types will remain unchanged, however additional numbers of gear may be added.
A recovery box will be used to condition the captured fish prior to release in Lac de Gras. DDMI and its construction contractors may undertake a controlled angling program to assist the fish salvage.
The following information will be collected:
a) Salvaged fish – capture information, species, weight and length estimate (all fish), weight measurement (0.1g) and fork length measurement (mm) for 1 in 5 fish. Species such as burbot and slimy sculpin are measured for total length only.
b) Fish mortalities – additional information to include sex, maturity and reproductive status.
c) Capture information – equipment set and retrieval time and date, location (UTM), depth at start and finish of trap net leads and gill nets (from measurement or bathymetric map), length and height of trap net leads and gill nets, surface water temperature.
d) Water quality – weekly profile at fixed deep location for temperature, dissolved oxygen, pH and turbidity.
Document#: CLSR-002-0513-R3 Page 54 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
During this initial period of fish salvage (also known as the CPUE Phase) no water will be removed from the dike area.
Towards the final week of the salvage program, DFO may request that final effort shift from CPUE to an intensive “Final Removal Phase”. This would involve maximizing the fishing effort and use of 24 hour sets. A21 pool dewatering may begin during this phase and may assist by concentrating fish. All fish would be processed as mortalities. All mortalities will be provided to local communities for their use.
The salvage program will be deemed complete if either:
a) declining CPUE has been demonstrated with sufficient fishing effort being employed, and no fish are captured with 24 hr of continuous netting/trapping, fishing gear are removed for 24 hr and then re-deployed for 24 hr of continuous fishing with no fish capture, or,
b) if pool dewatering has created an unsafe condition for fish crews as deemed by DDMI Site Safety Manager.
Daily reports will be prepared which summarize results for the day (total fish caught by species, % survival, CPUE) and any changes anticipated for the next day. These reports will be forwarded by email to DFO. A final report will be prepared in the form of a Data Summary Report that includes all methods, detailed results, and recommendations for improvements. Analysis will include estimates of total fish population using at least the Leslie and DeLury methods. An electronic copy of all data (MS-Excel), copies of all field notes and photographs will be provided to DFO.
Document#: CLSR-002-0513-R3 Page 55 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
13.0 A21 – REGULATORY SAMPLING – DIKE CONSTRUCTION
13.1 Daily Sampling Total suspended solids and turbidity monitoring are required by both the Fisheries Authorization and the Water License. The sampling locations are common to both however the collection method and results analysis methods differ.
Following are the methods, approved for the A154 and A418 dike construction by both the past Water Board (MVLWB) and DFO, with only the sampling locations modified.
As soon as ice conditions on Lac de Gras (2015 and 2016) have been deemed safe for boating by DDMI’s Site Safety Superintendent, fixed sampling locations will be marked with buoys. The coordinates for the sample locations are shown in Table 13.1. Daily, weather conditions permitting, each sampling location will be inspected by boat. A depth profile of turbidity will be measured at each sampling location using a calibrated HydroLab. Results will be reviewed at each site to determine the depth at which the highest turbidity reading was obtained. One water sample will then be collected from this depth, for the Fisheries Authorization, using a Van Dorn sampler. The midpoint on the Van Dorn sampler will be located at the depth of highest turbidity. This sample will be analyzed for total suspended solids at DDMI’s on-site lab using standard methods approved by the previous board (MVLWB).
A second water sample will be collected from each sampling location, for the Water License using an integrated depth sampler as specified in SNP Part B Item 23. This sample will be analyzed for TSS and turbidity using standard methods approved by the MVLWB.
Table 13.1: Fixed Sampling Locations Sample Location Northing Easting 1645-55 7 151 091 537 393 A21-A 7 148 731 534 190 A21-B 7 148 982 534 523 A21-C 7 149 480 534 584
Each day turbidity profiles and TSS results will be entered into DDMI’s database. For the Fisheries Authorization the measured TSS value from the maximum turbidity depth at each sampling location will be used to calculate a moving 110 day average value. On Day 1 that value will be calculated as the measured value from Day 1 divided by 110 as the previous 109 days are assumed to be 0 mg/L TSS. On Day 2 the value will be calculated as the Day 1 value plus the Day 2 value divided by 110 and so on. On days when weather conditions at site create unsafe conditions for boating, for the purpose of calculations, this missing data will be filled in by one of two methods. At the two sampling locations where remote monitoring equipment have been installed (see Remote Monitoring below) the highest of the three turbidity recordings (three depths) at 10:00 am will be converted into a TSS value using an established TSS:Turbidity relationship (see Remote Monitoring below). This calculated TSS value will then be used as the TSS value for that day. At the locations where remote monitoring equipment is not available, the value for the day will be assumed to be the same as the measured value from the previous day.
Document#: CLSR-002-0513-R3 Page 56 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
At the end of each day a data report similar in format to Table 13.2 will be prepared. The Table will be posted daily on an access controlled Web page.
Table 13.2: Sample Format for Daily Reporting – Fisheries Authorization Sampling Date: Sample Location Depth Turbidity (NTU) TSS (mg/L) 110D Avg. 1645-55 A21-A A21-B A21-C
For the Water License, the difference between the measured TSS value from the depth integrated sample the sampling location (A21A-C) and the background (1645-55) will be used to calculate a moving 30 day average value. On Day 1 that value will be calculated as the measured value from Day 1 divided by 30 as the previous 29 days are assumed to be 0 mg/L TSS. On Day 2 the value will be calculated as the Day 1 value plus the Day 2 value divided by 30 and so on. On days when weather conditions at site create unsafe conditions for boating, for the purpose of calculations, this missing data will be filled in by one of two methods. At the sampling locations where remote monitoring equipment have been installed (see Remote Monitoring below) the highest of the three turbidity recordings (three depths) at 10:00 am will be converted into a TSS value using an established TSS:Turbidity relationship (see Remote Monitoring below). This calculated TSS value will then be used as the TSS value for that day. At the locations where remote monitoring equipment is not available, the value for the day will be assumed to be the same as the measured value from the previous day.
At the end of each day a data report similar in format to Table 13.3 will be prepared. The Table will be posted daily on an access controlled Web page.
Table 13.3: Sample Format for Daily Reporting – Water License Sampling Date: TSS Increase over 30-d Average TSS Sample Location Depth Background (mg/L) (mg/L) 1645-55 A21-A A21-B A21-C
Figure 13.2 shows how the daily results will be used in construction management. An identical process was approved for the A154 and A418 dikes construction management.
Document#: CLSR-002-0513-R3 Page 57 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
13.1.1 Remote Monitoring
DDMI has two remote turbidity monitoring units that were used successfully during the A154 and A418 construction. These are self contained units with a surface buoy, three turbidity probes located at three depths along an anchoring system. Each unit is equipped with data loggers and telemetry systems to allow results to be obtained from a base station. The units will be anchored at two of the fixed monitoring locations. Initially they will be anchored at A21-A and A21-B as these locations are closest to the initial dike construction activity. Weekly the locations will be reviewed based on the daily monitoring results, the weekly plume delineation study (see below) and the dike construction schedule. The intent is to locate the units where TSS plume concentrations are highest or most likely. Any changes in location will be reported with the weekly plume delineation results.
Turbidity measurements from the remote units will be used when weather conditions prohibit sampling by boat (see above). TSS versus turbidity relationships will be developed to allow an estimation of the TSS concentration. Initially the relationships from the A154 dike construction monitoring will be used. Weekly this database will be expanded using the paired TSS and turbidity measurements collected from the daily sampling and weekly plume delineation study and a new ratio calculated. Weekly a graph showing the TSS:turbidity relationship will be reported with the plume delineation results.
13.2 Plume Delineation Monitoring Weekly, following the commencement of the daily sampling, sampling will be conducted to determine the location of any sediment plume as was done with the A154 dike construction. The planned method is to take measurements from a grid of sampling locations. The locations would be field determined based on numerous variables including location of construction activity, results from fixed location monitoring, wind/current direction, visual observation and results obtained during the survey. The objective is to define the area where turbidity concentrations are greater than 10 NTU. As many sampling locations as practical will be investigated both inside and outside of the dike alignment. At each sample location a HydroLab will be lowered through the water column. As the unit is lowered through the water column it continually (every 15 seconds) records the UTM coordinates of the unit, the depth, and the turbidity. Water samples (6 to10) will be collected from areas covering a range of turbidity levels. These samples will be analyzed in the lab for turbidity and TSS. The TSS and turbidity results will be used for the ongoing development of a TSS:Turbidity ratio.
Turbidity results will be input into a computer program to produce turbidity concentration isopleths maps. Three maps will be produced; one for the near surface (80% of depth), one for the mid water column (50% of depth) and one for the bottom layer (20% of depth). A summary table of statistics will be provided as similar to Table 13.5.
Document#: CLSR-002-0513-R3 Page 58 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Table 13.4: Sample Table for Plume Delineation Statistics <10 NTU 10-25 NTU 25-50 NTU >50 NTU Sampling Date: Ha % Ha % ha % ha % Area within silt curtain Area outside silt curtain Total Area of deep water habitat Area of shallow water habitat Area of shoal/shoreline habitat Total
Results, as isopleth maps and table of summary statistics will be posted weekly on an access controlled web site.
13.3 Sediment Deposition Monitoring Four sediment traps will be installed in each of 2015 and 2016 as soon as ice conditions on Lac de Gras have been deemed safe for boating by DDMI’s Site Safety Manager. The sediment traps will collect depositional sediments until late September when the traps will be recovered. Sediment trap details are shown in Figure 13.1. The lower trap will be positioned such that the bottom of the trap is within 1 m of the lake bottom, the middle trap will be located mid water column and the top trap will be positioned 2 m below the surface. The contents of the traps will be analyzed to determine the amount of particulate material and if sufficient quantities exist, the grain size distribution. Sediment trap coordinates are provided in Table 13.6, and the locations shown on Figure 7.1.
Table 13.5: Sediment Trap Locations Location ID Northing Easting Trap #1 (at 1645-55) 7 151 091 537 393 Trap #2 (at A21-A) 7 148 731 534 190 Trap #3 (at A21-B) 7 148 982 534 523 Trap #4 (at A21-C) 7 149 480 534 584
Document#: CLSR-002-0513-R3 Page 59 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 13.1: Sediment Trap Details
Document#: CLSR-002-0513-R3 Page 60 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 13.2: Flow Chart for the Regulatory Control of Total Suspended Solids
Document#: CLSR-002-0513-R3 Page 61 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
14.0 POOL DEWATERING
14.1 Objective The objective of this section is to provide a description of the activities and the environmental management controls that will be used during the drawdown of the water level in the pool formed behind the A21 dike.
14.2 Overview of Dewatering Activities 14.2.1 Dewatering Concept
In order to expose the A21 kimberlite pipes for open pit mining, the water contained by the A21 dike must be removed.
Water will be pumped directly from the A21 pool to Lac de Gras as long as water quality does not exceed the discharge limits defined in the Type A water license issued by the Wek’èezhíi Land and Water Board (License Number W2007L2-0003). When the A21 pit water is no longer in compliance with the water license discharge requirements, it will be pumped to on-land storage and treatment facilities, namely the NI. The water will be held in the NI until it is treated to meet discharge water quality criteria and then released into Lac de Gras.
The activities for the A21 pool dewatering have been planned using conservative assumptions regarding the pool water quality. The baseline scenario used for planning assumes that 50% (volume estimate) of the pool water will meet discharge criteria and will be pumped directly to Lac de Gras. The remaining 50% (volume estimate) of the pool water has been assumed to not meet discharge criteria, and will be pumped to the NI for storage, and subsequent treatment, prior to discharge to Lac de Gras.
This baseline scenario is considered conservative for the following reasons:
• Available measurement of the water quality in the A154/A418 pool shows that discharge limits had been met during the A154/A418 construction phase.
• Care will be exercised throughout 2015, 2016 and 2017 construction activities to avoid disturbing the water quality.
• Approximately 74% of the A418 pool was able to be discharged directly to Lac de Gras before water quality criteria dictated pumping to on-land storage.
• The lessons learned from the favourable experience with the A418 dewatering will be applied in the detailed planning and execution of the A21 pool dewatering.
14.2.2 A21 Pool Dewatering
One or two flexi-float barges will be used to dewater the A21 pool. The barges will be set up over the deepest point in the A21 pool, the bathymetric low between South Island and the A21 kimberlite pipe.
Document#: CLSR-002-0513-R3 Page 62 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
The discharge pipe line(s) will direct the pumped water to either Lac de Gras or to existing on land containment facilities. The discharge line into Lac de Gras will float so as not disturb the bottom of the lake (see Figure 14.1). The end of the discharge lines into both Lac de Gras and the containment facilities will be of sufficient length and positioned to avoid erosion of the containment dams.
Figure 14.1: Floating Discharge Facilities for Direct Discharge to Lac de Gras
The following construction activities are planned in advance of the A21 pool dewatering:
• Draw down of the North Inlet water level (2017) in preparation for A21 pool dewatering.
• Construction of the A21 dike, including monitoring instrumentation (2015-2017).
• Commission, assemble and install barges, pumps (summer 2017) and transfer pipelines (summer 2015).
• Discharge Destination:
- Water meeting environmental requirements: to Lac de Gras.
- Water not meeting environmental requirements to NI.
The dewatering of the A21 pool is planned to proceed in the following sequence:
• A21 pool water quality will be tested for all parameters as required by the water license, to ensure that initial volumes to be pumped will meet discharge criteria.
Document#: CLSR-002-0513-R3 Page 63 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
• Pumping of the A21 pool to Lac de Gras will commence.
• Ongoing testing will be conducted as required in the water license to monitor water quality during pumping, as described later in this report.
• When testing of pool water shows water quality has reached the maximum discharge criteria, discharge from the pumps will be re-routed.
• The remaining pool water will pumped to the NI and, subsequently treated by the NI water treatment plant.
• The total amount of water that can be managed this way is a function of the active storage volume in the NI, the excess NIWTP capacity and the rate at which the turbid pool water is to be pumped.
• As the pool is drawn down the pumping rate is determined by the pore water pressure response within and below the dike as identified by the instrumentation. Threshold levels in terms of monitored pore pressures, established in advance on the basis of stability analyses of the dike, will allow the rate of drawdown to be increased, decreased, or temporarily shut down as dictated by the Dike Engineer.
• If there isn’t sufficient time or capacity to route all of the turbid water to the NI then the next option will be to pipe the water to the PKC. The PKC dams will have considerable (>1Mm3) available capacity. This water would be used as make up water within the processing plant, reducing demands on Lac de Gras for this purpose. Routing of A21 pool water into the PKC facility is viewed as an opportunity/contingency only, the baseline plan being routing all water unsuitable for direct discharge to the NI.
The dewatering schedule for the A21 pool is approximately 180 days with a maximum drawdown rate of the water’s surface elevation of 400 mm per day. Experience gained during dewatering the A418 dike has shown that it is possible to exceed the rate of 400 mm per day given the appropriate pore water response within the dike and dike foundation. Drawdown rates in excess of 400 mm per day may be undertaken on the basis of favourable instrumentation data from the dike foundation, as determined by the Dike Engineer.
14.2.3 Regulatory Activities
A21 dewatering will not commence before the approval of this Plan by the Wek’èezhìi Land and Water Board. SNP Locations will be established and approved by the Inspector. The three sampling locations will be designated 1645-41’a’ through ‘e’ inclusive, with discrete depth samples collected every 2 m of depth, starting at surface.
Prior to dewatering, water quality results for the A21 Pool will be submitted to the Inspector as per Water License Part E Item 4. Samples will be collected as per SNP Part B Item 16a.
DDMI will notify the Inspector at least 5 days prior to the commencement of discharge to Lac de Gras, as per Water License Part H, Item 6.
Document#: CLSR-002-0513-R3 Page 64 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
During the period when pool water is being discharged to Lac de Gras, daily water samples will be collected from each SNP location as per SNP Part B, Item 16b, and every 6 days as per Item 16c.
Immediately following the termination of A21 pool water direct to Lac de Gras discharge, pool water samples will be collected and analyzed as per SNP Part B, Item 16d.
See also Section 7 for detailed description of monitoring requirements.
14.3 Pool Water Volumes and Distribution 14.3.1 Water Volumes
The volume of pool water is estimated at 6.1 Mm3. Allowance for precipitation, entrapped water within the downstream rock fill of the A21 dike, potential seepage through the A21 dike during pumping and additional volume created by previous dredging work to remove sediment from the A21 pit area, have also been added to the estimated volume of pool water to define the total water to be pumped. The total estimated water within the A21 pool to be removed during the dewatering is 6.7 Mm3. The breakdown is as follows:
• A21 pool => 6.11 Mm3 • Precipitation => 0.22 Mm3 • Entrapped water => 0.13 Mm3 • Seepage water => 0.2 Mm3 • Sediment removal => 0.06 Mm3 TOTAL 6.7 Mm3
14.3.2 Water Distribution and Storage
Based on the A154 and A418 experience, greater than ~60 percent of the pool water will be pumped directly over the dike to Lac de Gras. The balance of the pool water will be pumped to on-land storage facilities. The assumed distribution of the pool water, based on the conservative planning (in terms of on-land water storage requirements, with only 50% assumed for direct discharge to Lac de Gras) is as follows:
• Direct to Lac de Gras => 3.35 Mm3 = (50%)
• NI/NIWTP => 3.35 Mm3 = (50%)
TOTAL 6.7 Mm3
Measures will be taken to maximize the percentage of the pool water that is of acceptable quality for direct discharge for Lac de Gras. These measures, which may include turbidity barriers internal to the A21 pool, will be field determined.
Document#: CLSR-002-0513-R3 Page 65 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
14.3.3 Water System Layout
The layout of the facilities as they relate to the A21 pool dewatering activity is shown on Figure 14.2.
14.3.4 Pump-out Rates
The maximum pump-out rate for the A21 pool is governed by the draw down rate established by the A21 dike designers. This rate is a target established by the A21 dike designers to allow for safe pore water pressure dissipation in the dike’s foundation. Piezometers (instruments that measure pore water pressure) will be installed in the A21 dike to monitor actual pore pressure dissipation, and the drawdown rate will be adjusted in the field accordingly. The A418 experience indicated that more rapid drawdown rates were safely achieved on the basis of monitored instruments.
The elevation versus storage volume for the A21 pool, accounting for the pool, entrapped water (within the void spaces of the downstream shell of the dike) and lakebed sediments removal (downstream of the cut-off wall) is shown in Figure 14.3. Based on a 0.4 m/day drawdown rate, and a 0.8 m drawdown rate (found tolerable for A418 based on piezometers monitoring), the maximum pump out rates would occur at the onset of initial dewatering. Due to the shape of the elevation versus storage volume curve, the daily rate of pump-out would thereafter decrease.
Document#: CLSR-002-0513-R3 Page 66 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 14.2: Dewatering Pipeline Alignments
Document#: CLSR-002-0513-R3 Page 67 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 14.3: Elevation vs. Storage Volume for A21 Pool
Document#: CLSR-002-0513-R3 Page 68 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
The pumps are currently designed to operate at 54,000 m3/d when pumping to Lac de Gras and 30,000 m3/d when pumping to the North Inlet. These rates are less than the maximum drawdown rates and maybe revised depending upon the dike completion dates and pre- stripping schedule. The range of pump-out rates, based on a lower bound driven by 0.4 m/day drawdown, and an upper bound driven by 0.8 m/day drawdown, are given in Figure 14.4 below.
Figure 14.4: Range of Pump-Out Rates During Direct Discharge Phase to Lac de Gras
14.4 Discharge Structures 14.4.1 On-Land Storage Facilities
Discharge points into on-land facilities will have the end of pipe located inside each facility to avoid any potential erosion of containment structures or natural slopes. Rock armouring will be used to dissipate energy and prevent erosion at discharge sites.
14.4.2 Lac de Gras
The discharge line crossing the crest of the dike shall be securely fastened to a dissipation barge moored in Lac de Gras, approximately 20 meters from the dike. The discharge location
Document#: CLSR-002-0513-R3 Page 69 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
shall be in deep water and the distance from the dike will mitigate concerns for erosion. The ends will be anchored to ensure that the pipe does not move.
14.4.3 Inspections
Visual inspections will be conducted daily by the Contractor to monitor the integrity of the pumping systems and the performance of the armoured channels and dissipation barge. As a minimum, the inspections will be conducted twice daily, in the day shift and in the night shift. DDMI Environmental will conduct visual inspection of the water transfer system for leaks and surface erosion.
14.5 Monitoring 14.5.1 Water License Discharge Criteria to Lac de Gras
All discharges to Lac de Gras directly over the dike will meet the following effluent quality criteria as stated by the water license:
Maximum Average Maximum Concentration of Any Parameter: Concentration: Grab Sample:
Total Ammonia 6 mg/L 12 mg/L Total Aluminium 1.5 mg/L 3.0 mg/L Total Arsenic 0.05 mg/L 0.10 mg/L Total Copper 0.02 mg/L 0.04 mg/L Total Cadmium 0.0015 mg/L 0.0030 mg/L Total Chromium 0.02 mg/L 0.04 mg/L Total Lead 0.01 mg/L 0.02 mg/L Total Zinc 0.01 mg/L 0.02 mg/L Total Nickel 0.05 mg/L 0.10 mg/L Nitrate 1.0 mg/L 2.0 mg/L Total Suspended Solids 15.0 mg/L 25.0 mg/L Turbidity 10 NTU 15 NTU PH 6.0 (min) 8.4 (max)
The water license requires that the following sampling be conducted at Station Number 1645- 41: Once prior to the commencement of discharge at a minimum of five (5) stations evenly spaced along a longitudinal transect as approved by an Inspector. At each station, samples will be collected at surface and at 2 meter vertical intervals to depth and analyzed for the following:
• pH 4
• Total Suspended Solids
• Field Parameters 3
• Turbidity
• ICP-MS Metal Scan 1 (Total)
Document#: CLSR-002-0513-R3 Page 70 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
• Nutrients 5
• Major Ions 2
• Surface samples for Total Petroleum Hydrocarbons
a) Daily during dewatering and analyzed for the following:
o pH 4
o Turbidity
o Total Suspended Solids
o Total Phosphorus
b) Every six (6) days during dewatering and analyzed for the following:
o Field Parameters 3
o Nutrients 5
o ICP-MS Metal Scan 1 (Total)
o Oil and Grease (surface only)
o Major Ions 2
c) Once on the final day of dewatering at each of the five locations and analyzed for thre following:
o pH 4
o Total Suspended Solids
o Field Parameters 3
o Turbidity
o ICP-MS Metal scan 1 (Total)
o Nutrients 5
o Major Ions 2
o Surface samples for Total Petroleum Hydrocarbons
Document#: CLSR-002-0513-R3 Page 71 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
d) Additional sampling will be conducted if required by the Inspector:
o ICP-MS Metal scan shall include at a minimum, the following regulated parameters: aluminium, cadmium, chromium, copper, lead, nickel and zinc. Total metals will be analyzed unfiltered and dissolved using a 0.45 micron filter.
o Major ions will include the following parameters: calcium, chloride, sulphate, sodium, magnesium, fluoride, alkalinity, and potassium.
o Field measurements shall include the following measurements: pH, conductivity, and temperature.
o pH analyzed in the laboratory.
o Nutrients include the following parameters: total ammonia, nitrate-nitrogen, nitrite- nitrogen, total phosphorus, total dissolved phosphorus, ortho phosphorus, total Kjedal nitrogen.
14.5.2 SNP Sampling Program
DDMI will conduct the following sampling to satisfy the requirements of the water license:
a) Prior to discharge, field parameters will be collected by Hydrolab surveys (multiprobe water quality field instruments) at the specified stations, locations and depths. A discrete sampler such as a Beta bottle grab samples will be also be taken at the noted stations, locations and depths to be analyzed on-site for pH, turbidity and TSS and for all other parameters at an off-site third party laboratory.
b) Daily during dewatering, Beta bottle grab samples will be also be taken at the noted stations, locations and depths to be analyzed for pH, turbidity, TSS and phosphorous. Where possible TSS, turbidity and pH will be analyzed at the on-site laboratory. Total phosphorus will always be analyzed off-site. If the number of samples exceeds the capacity of the on-site laboratory for TSS, turbidity and pH, samples will be sent off-site for analysis.
c) Every sixth day of dewatering, field parameters will be collected by Hydrolab surveys. Beta bottle grab samples will also be taken to be analyzed on-site for pH, turbidity and TSS and for all other parameters at an off-site third party laboratory.
d) The final day of dewatering in which discharge will be directed to Lac de Gras, field parameters will be collected by Hydrolab surveys at the specified stations, locations and depths. Beta bottle grab samples will be also be taken at the noted stations, locations and depths to be analyzed on-site for pH, turbidity and TSS and for all other parameters at an off-site third party laboratory.
Document#: CLSR-002-0513-R3 Page 72 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
14.6 Management Plans 14.6.1 Site Responsibilities
Diavik Diamond Mines Inc. (DDMI), as the business Owner and Project Operator, has overall responsibility for implementing this plan. This includes all of the physical works associated with the draw down activities as well as Quality Control and Environmental Management of their work.
DDMI is responsible for the following items:
• Provide all liaisons with the regulatory authorities.
• DDMI site staff will be responsible for all water sampling.
• Provide the construction team with water quality test results.
• Approve recommendations made by the Designer and Engineer during dewatering and/or modify.
• Management of the dewatering work to minimize the generation of pool water turbidity and maximize the volume of water discharged to Lac de Gras.
• Conduct daily surveys to measure A21 pool draw down.
• Conduct daily surveys to measure accumulated volumes in the NI.
• Advise Contractor of on-land storage elevations and corresponding available remaining capacity volumes.
• Quality Assurance for the Contractor’s work, including Environmental Management.
• Remove the pool water.
• Hydraulic design of the pumping system.
• Supply and installation of pumps, pipelines and instrumentation.
• Operate and maintain the pumping system.
• Quality control work, including Environmental Management and completion of inspections.
14.6.2 Decision Making
Decision Point 1 - Cease Discharge to Lac de Gras
The primary decision to be made during the dewatering operation is when to discontinue discharging pool water to Lac de Gras and divert to on-land storage facilities. Direct discharge
Document#: CLSR-002-0513-R3 Page 73 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
to Lac de Gras will continue as long as the pool water is within the discharge criteria limits. Measures will be implemented prior to and during dewatering to maximize the period of time for which this is achieved.
The DDMI Project Manager will be responsible for making this decision. DDMI site environmental staff will provide the Project Manager with water quality test results from the relevant SNP site as available from the on-site lab or from off-site third party labs. Upon receiving this data, the Project Manager and DDMI Environment will interpret the data in light of this management plan and make a decision to stop discharge to Lac de Gras and divert pumping discharge to on-land storage facilities.
Decision Point 2 - Draw Down Rate
The preliminary draw down for the pool dewatering is 400 mm per day, as per the Dike Engineer. Actual pore pressures will be monitored by the Dike Engineer during draw down. The draw down rate will be governed by the response of pore water pressure and other indicators such as water levels within the relief wells.
The Dike Engineer (BGC) will be responsible to make a decision regarding increasing or decreasing the rate at which the pool is drawn down. These decisions will be facilitated by having available in advance of dewatering, based on geotechnical stability analyses, threshold piezometer levels (as a function of pool elevation) defining acceptable versus unacceptable conditions. If pore pressures dissipate differently than anticipated, the draw down rate will be re-assessed by the Dike Engineer and a recommendation provided to DDMI to change the maximum allowable draw down rate.
14.6.3 Fuel Handling
Mobile fuel trucks will be used to refuel the pumps. A floating walkway will provide access from the shore to the floating pump barge. Mobile fuel trucks will drive to the end of the walkway and pump through an Arctic grade steel lined heavy wall fuel line to a double lined day tank on the barge via the walkway. The fuel is pumped through a “Wiggens” system that has a drip tray at the connection point between the fuel truck and the fuel line. Diesel engines will have drip tray type containment around them to contain any spills or leaks. This system was used for construction of both the A154 and A418 dikes and has provided to be robust. No fuel spills occurred that impacted the water quality in Lac de Gras.
Spill prevention and management will be in place in accordance with the existing contingency plan.
In the event that greater volumes of water are encountered during dewatering than planned, the dewatering rates and schedule will be altered to match the treatment rate of the NIWTP, so that the pumping and storage volumes remain balanced.
14.6.4 Wildlife Management
The activities associated with drawdown are not anticipated to have any impact on wildlife in the area. Wildlife management procedures currently in place for construction activities will continue to be enforced and monitored.
Document#: CLSR-002-0513-R3 Page 74 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
14.6.5 Environmental Issues
Potential impacts during the dewatering operations are as follows:
• Potential for water with high TSS being pumped into the lake thus affecting aquatic resources.
• Fish trapped behind the dike could perish as fresh water is pumped out.
• Rapid discharge of water into the open lake can lead to disturbance of the lakebed sediments and increased turbidity.
14.6.6 Management Measures
In order to minimize or eliminate the potential impacts identified in the previous section, the following actions will be implemented:
• Water samples will be collected on a regular basis at the location of a monitoring station, which will continuously analyze water quality. Discharge into Lac de Gras will only be done when the TSS criterion is satisfied. Otherwise, water will be transferred to the NI.
• A fish-salvaging program will be established in consultation with the local communities and the regulatory agencies. The program will include live netting of fish and releasing them back into Lac de Gras outside of the dike. (See Technical Procedure No. 2.1-1, Fish Salvage and Collection Method in Diavik Procedures.) This method of fish collection has been used during Stage 1 after obtaining the DFO Fisheries Authorization.
14.6.7 Monitoring and Controls
To control the mitigation measures identified, the following actions will be necessary:
• Daily monitoring will be conducted as per DDMI Water License at SNP station 1645-40. Both water samples and biophysical measurement will be taken and correlated.
• As may be necessary, the dewatering contractor will be required to modify the position of the pump barge to optimize the quality of the water being pumped.
14.7 Summary Report Within sixty (60) days of the completion of the A21 pool dewatering, a summary report will be prepared and submitted to the Board. The report will contain the following:
a) Volumes Pumped - A final water balance will be provided giving estimates of the total quantity of water pumped, stored and treated.
b) Monitoring Results - The results of water quality monitoring and an evaluation of compliance with the regulated water quality requirements will be provided.
Document#: CLSR-002-0513-R3 Page 75 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
c) Mitigative Actions - A description of any water treatment undertaken, erosion problems encountered and/or mitigative actions taken.
Document#: CLSR-002-0513-R3 Page 76 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
15.0 SPILL RESPONSE ON LAND AND IN LAC DE GRAS
15.1 Spill Response On-land This Emergency Spill Response plan provides procedures for responding to a fuel oil or hazardous chemical spill at the job site. The plan includes provisions for safety, call out procedures, physical response procedures, reporting procedures, and the necessary instructions for implementing the plan.
Although this plan establishes a framework for response, should a spill occur the philosophy is that preventing / containing spills is very much more preferable to responding to them.
This philosophy is implemented in the following manner:
• All bulk fuel storage areas include double walled storage tanks or have lined secondary containment dikes surrounding them (a.k.a. bunding). These dikes are constructed of either concrete or compacted earth provided with HDPE or bituminous liner and have at least 110% containment capacity of the largest tank contained within them.
• A daily inspection program has been established to inspect all bulk storage tanks and containment dikes utilized by the contractors. DDMI will perform weekly audits of these storage tanks and containment dikes.
Response Authority
The site supervisor has the responsibility for the initiation of the Emergency Spill Response plan in the event of a hazardous material spill. The supervisor will be responsible to manage and direct the containment and cleanup procedures and contact the senior members of the management team.
Note: The site supervisor has the authority to purchase or procure any labour, contract services, materials, and/or support services required to meet the situation.
Employee Safety
Before responding to any spill, the safety of all personnel must be assured; therefore, the following steps shall be taken before beginning the response:
1. Notify the Safety Department. 2. Identify the spilled material and follow the appropriate procedure. 3. Fuel Oils, Diesel, Gasoline, Aviation Fuel.
a.) Monitor the area for Explosive gases (LEL) and Oxygen (O2) to ensure a safe atmosphere.
b.) Determine the potential for fire, and eliminate any hazards.
c.) Ensure that all personnel are equipped with the appropriate PPE.
Document#: CLSR-002-0513-R3 Page 77 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
4. Chemical Spills a.) Consult the Material Safety Data Sheets (MSDS) for the spilled material to determine the health effects and the requirement for PPE.
b.) Refer to the Contractor’s Spill Reporting Procedures Manual.
Spill Reporting Procedures
After ensuring the safety of personnel, proceed with the appropriate response to the situation.
• Spills or releases of hazardous substances into the environment may require notification to one or more federal or provincial agencies. The release reporting requirements are dependent on the substance released, the location of the release, and the period of time when the release occurred.
• Any spills of petroleum products on the water must be considered a reportable spill. Spills of hazardous materials or hazardous waste that exceed their reportable quantities are a reportable spill.
• The Contractor’s site supervisor should report the release immediately to DDMI Environment. The onsite supervisor will be responsible for submitting to DDMI an Environmental Investigation Report. DDMI’s Environment Department will utilize this report and, gather information about the release and report this information to the appropriate agencies. If there is doubt as to the volume of released material that has to be reported. The on-site DDMI Environmental coordinator will report the spill.
Response
Initiate containment of the spilled material.
a.) All spills should be intercepted and contained as close to the release point as possible. Absorbent booms and other absorbent materials are located in the job shop.
b.) Spills onto the ground may be contained using absorbent booms or other absorbent materials; constructing earthen dams, either by hand or with the use of equipment; blocking drainage culverts and inlets to drain systems, etc. Emphasis should be placed on keeping spilled materials from entering any water source. If the spill is in a field location, consult the job plans to determine the drainage system which may be affected and the location of the nearest downstream spill control pond.
c.) Spills that reach water may be contained by the use of booms, absorbent booms, earthen pipe dams (with the outlet controlled to allow the water to pass through the pipe subsurface), use of weirs, etc. Spills of produced water and other materials which are water soluble cannot be contained with any degree of success. Again, spills should be contained at the closest feasible point to the source.
Document#: CLSR-002-0513-R3 Page 78 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Begin Clean-up Operations
a) It is important to begin clean-up operations as soon as possible. The sooner clean-up begins, the higher the recovered amount of spilled material. This increases the recovery percentage and reduces environmental damage.
b) Spills onto Land: 1. Recovery of any liquid spill material is to be initiated immediately with a vacuum truck or absorbent pads or other absorbent materials. The material recovered should be returned to the system, if possible, or stored in sealed, leak-proof containers for subsequent handling.
2. After recovering any free liquids, flush the affected area with fresh water to increase the recovery. This technique is particularly effective for partial recovery of highly soluble materials or light oils but is not effective on heavy or insoluble materials. Take care to avoid dispersing the materials across a larger area.
3. Heavy oils and some oils contained in paraffin may be recovered by scooping up the material with hand tools or equipment. Subsequent flushing of the affected area with hot water while recovering the spilled material may increase the recovery. Again, take care to avoid spreading the material over a larger area.
4. During winter, snow that is contaminated with spilled material may be stockpiled in a lined, contained area, to be recovered after the snow has melted.
5. Some spilled materials may be made less harmful to the environment if a chemical neutralizer is applied. The MSDS for the material may list appropriate neutralizer(s) for a substance. Consult with the Environmental Coordinator to identify the proper neutralizer to use. Other clean-up efforts may be used after consulting with the Environmental Coordinator and other appropriate Crisis team personnel, such as the Safety Department. Removal of contaminated soils without the authorization of the Crisis Team Leader is now allowed. c) Spills into Water: 1. Spills of oil into water may be recovered by using skimmers, skimming pumps, absorbent materials, and vacuum trucks. Spills of soluble materials (such as produced water) into water may only be recovered by damming the discharge involved and recovering all of the affected water. This technique is not effective for anything other than a small discharge.
2. Cleaning of bank areas can be done with techniques similar to those used for recovery of spills onto land. Neutralizers for chemical spills into water may be used if approved by the Environmental Coordinator and/or Operations Center Foreman. Use of dispersants for oil spills to water requires governmental approval and will not occur without approval from both the Project Superintendent and the Environmental Coordinator.
3. Other techniques for clean-up of spills into water may be identified by the Environmental Coordinator.
Document#: CLSR-002-0513-R3 Page 79 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Notification Procedures
Upon discovery that a spill event has occurred, the highest ranking Company employee on the scene shall evaluate the size, extent, and seriousness of the spill, then contact the Environmental Coordinator (or designee) immediately for all spill incidents. The On-Scene Commander will then decide whether to call those on DDMI’s Emergency Response Team (ERT).
The contractor shall utilize their own Emergency Response team for all spills which reach water and for all major spills onto land. If required DDMI’s ERT will be initiated to assist. The supervisor at the scene shall determine, based on the circumstances, if the Local Emergency Response team needs to be activated for medium or minor spills on land.
Remediation/Reclamation
Remediation and reclamation of the areas affected by a spill will be initiated after consulting with the appropriate District Office personnel and the Environmental Coordinator. The remediation and reclamation procedures used may be mandated by governmental actions or orders.
Disposal
Disposal of waste generated by spill-response actions is to be arranged by the contractor. The disposal process will be following DDMI’s mine site waste management system.
Reporting
DDMI Environment is responsible to make all required external reports regarding the incident. The Job Superintendent and DDMI Environment representative will also make the appropriate internal reports. Government agency reports must be made as soon as possible and always within 24 hours of an identified spill. A sample spill-report form for recording required information follows.
15.2 Spill Report Form Reportable Quantities
The following table is a summary of the volumes and reporting levels for spilled materials. A complete list of hazardous chemicals and their reporting levels is available from the DDMI Environment or Safety Department.
The Contractor is required to report all chemical spills to DDMI Environment as soon as possible. DDMI Environment will notify the appropriate Federal and Provincial Department of Environmental Quality and other government agencies. The information required to report a hazardous substance is as follows but not limiting to:
• The chemical name or identity of any substance involved in the release. Include the CAS number, if possible.
• Indicate if the substance is on the CERCLA or SARA list, or both.
Document#: CLSR-002-0513-R3 Page 80 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
• Estimate the quantity released. If possible, note both the hazardous constituent and, if the material is a mixture, the mixture quantities.
• The time and duration of the release. If it is ongoing, estimate the time that it will stop and the environmental medium or media into which the release occurred.
• Any known or anticipated health risks – acute or chronic – associated with the substance and, where appropriate, advise regarding medical attention necessary for exposed individuals. Be cautious – it is better to say you don’t know than to guess.
• The proper precautions to take as a result of the release, including evacuation.
• The names and telephone numbers of the Contractor’s personnel to be contacted for further information.
• Any clean-up, containment, or control activities in progress, and a statement whether outside help will be required.
• The location of the release (Section, Township, Range, County, and Province (Fed. Calls).
Decontamination
At the job site, Decontamination (or Termination) is a critical part of the conclusion to any emergency. Decontamination is the process by which potentially hazardous substances are removed from employees without adversely affecting their health and safety.
15.3 Spill Response in Lac de Gras by Contractor Initial Action
This section outlines the initial actions to be taken by the first persons arriving/witnessing to the scene of an accidental sediment discharge into Lac de Gras.
• If possible, identify the type of material spilled.
• Locate the spill source and assess if the spill can be readily stopped or brought under control.
• If safe to do so, and if possible, try to stop the flow of materials.
• Gather information on the status of the situation.
• Report the spill without delay to your immediate supervisor (see Figure. 14.1 – Spill reporting procedure chart).
• The immediate supervisor or representative (Environment / Safety Individual) will notify DDMI Environment.
Document#: CLSR-002-0513-R3 Page 81 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
• The Contractor’s representative will ensure the on-scene Coordinator mobilizes environmental personnel and resources.
• Record all relevant information for reporting purposes.
• Resume any effective action to stop the flow of the spilled material, to contain and clean up.
Accidental Sediment Discharge on Water
• Identify the source of the leak or spill.
• Contain the spill at the source.
• Stop the sediment discharge into Lac de Gras by the following actions:
Potential Sediment Discharge Source Action To Stop The Discharge Cease filling the containment dike.
Locate the source of the leak. Breach of Slurry Pond
Empty and clean the leaking part of the pond Repair the damaged part of the liner. Cease pumping through the pipeline and turn on safety valves. Break in the Pipeline Bleed the line back into the Slurry containment pond. Remove any excessive spilled material on the Overland Runoff into Lac de Gras dike by mechanical means. Overspilling of slurry from the jet grouting Grade working platform allowing slurry to drain operations into the trench. Cease grouting the hole and use thicker grout mix Grout leaks through the fill or foundation or accelerators.
• When possible, prevent any further contact with the water by berming, diking, trenching and blocking the entry to waterways down slope of the running sediment fluids by placing barriers.
• In case of major grout or slurry spill into Lac de Gras, turbidity curtains will be deployed to contain and to minimize the area contaminated by the spill.
Document#: CLSR-002-0513-R3 Page 82 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
• Remove the excessive spilled material on the dike using shovels, backhoes or any other mechanical methods.
• The incident must be immediately reported as per Figure 15.1 – Spill reporting procedure charts.
Equipment and Material for Response Plan
During the construction phase of the dikes, a container storing the materials required to respond to an accidental sediment discharge will be strategically located where required. The following equipment and material will be available to provide a quick response:
• Vacuum Truck ‘’Super Vac 2000 gallons’’.
• Submersible Trash Pumps 3’’ and 4’’ diameter.
• Work boat fully dedicated for the emergency situations.
• Additional turbidity curtain sections.
• Hand tools required for clean up.
• Wheel loaders and trucks for cleanup on the dike.
Document#: CLSR-002-0513-R3 Page 83 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Figure 15.1: Spill Reporting Procedures Charts – Construction Phase
DDMI Construction DDMI Environment Manager
DDMI – Contractor Spill DDMI - Contractor Safety Response Coordinator
Document#: CLSR-002-0513-R3 Page 84 Diavik Diamond Mines Inc. A21 Dike: 2014 Update Construction Environmental Management Plan 31 December 2014
Contractor Diavik A21 Project – Northwest Territories Environment
EMERGENCY RESPONSE REPORT
Site: Date:
No. Observations Actions Date
COMMENTS
By : Copy to :
Document#: CLSR-002-0513-R3 Page 85