PEI-NB Cable Interconnection Upgrade Project EIA: Marine ... · PDF filePEI-NB CABLE...

PEI-NB Cable Interconnection Upgrade Project EIA: Marine Supplemental Report No. 2

Investigation of Sediment Deposition/Transport and Water Column Turbidity

Prepared for:

Maritime Electric Company Limited 180 Kent Street Charlottetown PE C1A 1N9

Prepared by:

Stantec Consulting Ltd. 165 Maple Hills Avenue Charlottetown PE C1C 1N9

Job No. 121811475

February 23, 2016

PEI-NB CABLE INTERCONNECTION UPGRADE PROJECT EIA: MARINE SUPPLEMENTAL REPORT NO. 2

Table of Contents

1.0 INTRODUCTION ................................................................................................................ 1 1.1 SUMMARY OF CABLE INSTALLATION ................................................................................. 2

2.0 EXISTING CONDITIONS .................................................................................................... 7 2.1 METHODS .............................................................................................................................. 7

2.1.1 Current Profiling ................................................................................................. 7 2.1.2 Water Column Total Suspended Solids, Water Quality and

Sediment Particle Size ...................................................................................... 8 2.1.3 Baseline Sediment Deposition ...................................................................... 10

2.2 RESULTS ................................................................................................................................ 11 2.2.1 Bathymetry ....................................................................................................... 11 2.2.2 Tides and Meteorological Conditions ......................................................... 12 2.2.3 Measured Currents ......................................................................................... 13 2.2.4 Temperature, Salinity and Turbidity Data ................................................... 18 2.2.5 Total Suspended Sediments .......................................................................... 21 2.2.6 Sediment Particle Size .................................................................................... 21 2.2.7 Sediment Trap Results..................................................................................... 23

3.0 SEDIMENT DEPOSITION MODELLING ............................................................................. 24 3.1 APPROACH ......................................................................................................................... 24 3.2 METHODS ............................................................................................................................ 25

3.2.1 Modelled Scenarios ........................................................................................ 25 3.3 RESULTS ................................................................................................................................ 27 3.4 EXTENT OF SEDIMENT DEPOSITION ................................................................................... 32

4.0 SEDIMENT PLUME MODELLING ...................................................................................... 34 4.1 APPROACH ......................................................................................................................... 34 4.2 METHODS ............................................................................................................................ 34

4.2.1 Modelled Scenarios ........................................................................................ 34 4.3 RESULTS ................................................................................................................................ 35 4.4 SEDIMENT PLUME EXTENTS ................................................................................................ 36

5.0 SEDIMENT TRANSPORT ................................................................................................... 37 5.1 APPROACH ......................................................................................................................... 37 5.2 METHODS ............................................................................................................................ 37

5.2.1 Modelled Scenarios ........................................................................................ 37 5.3 SEDIMENT TRANSPORT RATES ........................................................................................... 38 5.4 TRENCH INFILLING .............................................................................................................. 39

6.0 SUMMARY ....................................................................................................................... 41

7.0 LIMITATIONS ................................................................................................................... 42


8.0 CLOSURE ......................................................................................................................... 43

9.0 REFERENCES.................................................................................................................... 44

LIST OF TABLES Table 1.1 Cable Excavation Methods for PEI – NB Interconnection ............................... 6 Table 2.1 Meteorological Data - PEI ................................................................................... 13 Table 2.2 Meteorological Data - NB ................................................................................... 13 Table 2.3 Nearshore Baseline Total Suspended Sediment Concentrations ................. 21 Table 2.4 Particle Size Distribution for PEI Sediment Samples ......................................... 22 Table 2.5 Particle Size Distribution for New Brunswick Sediment Samples .................... 22 Table 2.6 Baseline Sediment Deposition Rates (Oct – Nov 2015) .................................. 23 Table 3.1 New Brunswick Nearshore Model Inputs – Ebbing Tide .................................. 26 Table 3.2 New Brunswick Nearshore Model Inputs – Flooding Tide ............................... 26 Table 3.3 Distance to Outer Boundary of the 10 mm Deposition Layer ....................... 32 Table 4.1 Water Column Turbidity Modelling Inputs ......................................................... 35 Table 4.2 Summary of Water Column Turbidity Results .................................................... 36 Table 5.1 Sediment Transport Modelling Inputs ................................................................ 38 Table 5.2 Sediment Transport Rates .................................................................................... 39

LIST OF FIGURES Figure 1.1 Proposed Subsea Cable Installation Route ........................................................ 4 Figure 1.2 New Brunswick Nearshore Reroute ...................................................................... 5 Figure 2.1 Water and Sediment Sampling Locations within the

Northumberland Strait ............................................................................................ 9 Figure 2.2 Sediment Trap Design .......................................................................................... 10 Figure 2.3 Tide Levels at Port Borden and Cape Tormentine .......................................... 12 Figure 2.4 Current Velocities Measured in the Project Area – New Brunswick

Nearshore ............................................................................................................... 15 Figure 2.5 Vertical Profile (Direction and Magnitude) of New Brunswick

Nearshore Currents – Flooding Tide ................................................................... 16 Figure 2.6 Current Velocities Measured in the Project Area - PEI Nearshore ................ 17 Figure 2.7 PEI Water Quality Profiles (October 2015) ......................................................... 19 Figure 2.8 New Brunswick Water Quality Profiles (October 2015) ................................... 20 Figure 3.1 Predicted Material Deposited 2 hours Post Excavation during an

Ebbing and Flooding Tide at a Water Depth of 3 m ...................................... 28 Figure 3.2 Predicted Material Deposited 2 hours Post-excavation during an

Ebbing and Flooding Tide at a Water Depth of 8 m ...................................... 30 Figure 3.3 Predicted Material Deposited 2 hours Post-excavation for Maximum

Currents during Ebbing and Flooding Tides at a Water Depth of 8 m ........ 31 Figure A.1 Multibeam – Bathymetry (McGregor Geoscience 2015) Figure B.1 Site NB-1: Water Depth, 3 m; Currents, Surface 4.6 and Bottom 4.9 cm/s


Figure B.2 Site NB-3: Water Depth, 8m; Currents, Surface 9.6 and Bottom 7.7 cm/s Figure B.3 Site NB-3: Water Depth, 8m; Currents: Surface 113 and Bottom 85 cm/s

LIST OF APPENDICES

Appendix A Marine Geophysical Survey – Bathymetry

Appendix B TSS Model Results


Introduction February 23, 2016

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1.0 INTRODUCTION

In September 2015 Maritime Electric Company, Limited (MECL) submitted the Environmental Impact Assessment (EIA) to Prince Edward Island and New Brunswick provincial regulators for the construction and operation of an electrical transmission cable to supply power from New Brunswick to Prince Edward Island (Stantec 2015a). This project includes two new submarine cables that would traverse from Cape Tormentine, NB to Borden, PE and be buried in the substrate of the Northumberland Strait.

As a result of the regulatory review process of the EIA, information requests were received by MECL pertaining to the Marine Environment. The information requests in reference to the submarine cables could be generally characterized into the following environmental categories:

Sediment Deposition – Determine the extent of immediate deposition and dispersal of the excavated sediments.

Water Column Turbidity (Sediment Plume) – Determine the extent and concentration of the sediment resuspended during excavation and side casting.

Sediment Transport – Infilling of the trench will be conducted where the trench is excavated using the clam shell dredge in the nearshore. The trench excavation in the offshore using the TROV will not be infilled. As a result for the latter, determine the duration the trench will remain open.

To evaluate the sediment deposition, water column turbidity and sediment transport, Stantec adopted a near-field numerical modelling approach. The models to evaluate the Project were peer-reviewed and using accepted methods of quantifying the fate of excavated sediment.

Field data were collected to supplement the data collected for the EIA, with both sets of data used to support the modelling work.

This report documents the setup and application of the near-field numerical sediment plume and transport models to assess the potential deposition, dispersion and transport of sediment released during the proposed trenching operations.



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1.1 SUMMARY OF CABLE INSTALLATION

Two submarine cables transmitting 360 MW combined at 138 kV each will be installed below the seabed of the Northumberland Strait. The two cables will be installed in separate trenches, up to 200 m apart. The cables will be buried, where possible, to protect the cables from interactions with commercial fishing gear, anchors, ice scour and erosion. The method of excavation in the marine environment has been revised from that described in the EIA (Stantec 2015a).

A revised installation route was proposed by the cable installer and the marine engineer to avoid the shallow ridge located just outside the harbour in Cape Tormentine. The current route subsequent to the EIA) passes to the south of the ridge through deeper water (Figure 1.1. This will potentially allow a Trenching Remotely Operated Vehicle (TROV) to operate closer to shore and reduce the use of the clamshell bucket in the nearshore environment. The proposed route will in turn decrease the volume of sediment excavated for installation of the subsea cables by allowing more of the trench to be excavated using the TROV, which requires a smaller trench for installation of the cable. During the environmental assessment eelgrass habitat was noted and delineated in a supplemental report (Stantec 2015b). The revised trench locations will decrease the project footprint in the eelgrass habitat. This reroute and path through the eelgrass habitat is illustrated in Figure 1.2.

The current trenching plan includes the use of a marine excavator, a clam shell bucket, and potentially a TROV. Each method is designed to excavate the trench in different water depths. Starting on the New Brunswick side trenching will occur to a depth of 2.2 m below the seabed. This will involve the use of a marine excavator from 0 to -2 m water depth and a clam shell bucket from -2 to -8 m. This trench will be approximately 1 m wide at the bottom and rise at a 2:1 slope to a maximum width of 9 m. The clam shell bucket will excavate the trench prior to the installation of the cable. This requires the trench to be excavated to a width greater than the cable diameter to account for potential sediment infilling of the trench between the time of excavation and cable installation. Bedrock may be present near the surface in this section of the route. If encountered, excavation will stop once bedrock is encountered as long as a 1 m trench depth is achieved. If bedrock is encountered within 1 m of the seabed surface, excavation will continue into the bedrock until a 1 m trench depth is completed. Where this occurs trench dimensions will decrease with the trench approximately 1 m wide at the bottom; the trench width at the seabed will vary based on the material encountered but will generally be less than 9 m wide.

The seabed from -8 to -12 m is predominantly composed of glacial till; bedrock is not anticipated to be present within 2 m of the seabed surface (CSR 2014, McGregor 2015). Currently a feasibility assessment is being conducted for the section between -8 to -12 m water depth to determine the methods of excavation. If the substrate allows and a cable cover depth of 1.3 m is deemed acceptable for ice scour, a TROV will continue the trench to a depth of 1.6 m below the seabed. The trench resulting from the use of the TROV will be approximately 0.35 m wide. Based on operational limitations of the TROV and support vessel, the TROV cannot be used in water



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depths shallower than 8 m. If the feasibility study determines that the clam shell dredge is the appropriate excavation method, this method will be used to excavate in water depths from -8 to -12 m, as described in the EIA.

From -12 m water depth on the New Brunswick side to -12 m on the PEI side the use of a TROV will continue and the trench depth will decrease to 0.6 m below the seabed, maintaining a 0.35 m wide trench as previously indicated. In this section of the cable route the seabed is composed predominantly of glacial till (sand and gravel) (CSR 2014, McGregor 2015).

On the PEI side from -12 m water depth to the shoreline a trench up to 2 m deep will be completed using a clam shell bucket either mounted on a barge or an excavator from shore. The material along the PEI shore is predominantly bedrock and cobble with little overlying sediment (CSR 2014, McGregor 2015). In this section the trench is expected to be 1 m wide at the bottom with little slumping of the trench walls.

Proposed Subsea Cable Route

Figure 1.1

Area ofInterest

121811475 - PEI-NB Interconnection - Maritime Electric Company, Limited

U:\121811475\3_drawings\3_draft_figures\mxd\rpt\adcp\121811475_0067.mxd

Disclaimer: This map is for illustrative purposes to support this Stantec project; questions can be directed to the issuing agency.Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community, NB Power, Maritime Electric Company, Limited, Canadian Seabed Research (2014), Canadian Hydrographic Service (1972)

NAD 1983 CSRS UTM Zone 20N

Bathymetry, (m Chart Datum) Proposed Project Components

Proposed Transmission LineProposed Project Components in theNorthumberland Strait

Proposed Submarine Cable #4Proposed Submarine Cable #3Proposed Re-routingSubmarine Cable #4Proposed Re-routingSubmarine Cable #3

Bathymetry Depth Chart Datum (m)0 - 55 - 1010 - 1515 - 2020 - 2525 - 3030 - 35

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Figure 1.2

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1218111475 - PEI - NB Marine Cable Interconnection - Maritime Electric Company Limited

New Brunwick Nearshore Reroute

Disclaimer: This map is for illustrative purposes to support this Stantec project; questions can be directed to the issuing agency.Sources: Imagery: Bing - Microsoft product screen shot(s) reprinted with permission from Microsoft Corporation.Project Data from Stantec or provided by NB Power / MECL.

U:\121811475\3_drawings\3_draft_figures\mxd\pln\121811475-0064.mxd

NAD 1983 CSRS NBDS

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Plant Cover (%)01-1010-2020-3030-4040-5050-6060-7070-8080-9090-100

Project Study AreaProposed Project Components

Proposed Transmission LineProposed Buried Cable

Proposed Project InfrastructureProposed Project Components in theNorthumberland Strait

Proposed Submarine Cable #4Proposed Submarine Cable #3

Proposed Re-RoutingSubmarine Cable #4Proposed Re-RoutingSubmarine Cable #3

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Using the cable installation methods described above an estimate of the total volume of material to be side cast for each section is presented in Table 1.1. The estimated volume incorporates predictions of surficial sediment depth based on the depth to bedrock data obtained during the Marine Geophysical Survey (CSR 2014).

Table 1.1 Cable Excavation Methods for PEI – NB Interconnection

Section of Cable Route

Water Depth (CD)

Approximate Linear

Distance (per cable)

Approximate Trench Deptha

Approximate Trench Widtha

Approximate Material

Volume (both cables)b

Excavation Techniques

New Brunswick Near shore

(less than -12 m)

0 to -2 m 500 m 1 – 2.2 m 2 to 9 m 7,900 Shoreline

excavation (Excavator)

-2 to -8 m 1,450 m 1 - 2.2 m 2 to 9 m 26,800

Barge mounted excavator (Clam

shell bucket)

-8 to -12 m 2,600 m 1 - 2.2 m

0.35 m 3,400 TROV to 2 m below surface

↑ TROV or Clam shell bucket ↓

2 to 9 m 28,600 Barge mounted

excavator (Clam shell bucket)

Northumberland Strait (greater than -12 m)

> -12 m 11 km 0.6 m 0.35 m 4,600 TROV to 0.6 m below surface

PEI Nearshore (less than -12 m)

0 to -12 m 1,900 m 1 - 2.2 m 2 m 9,600

Barge mounted excavator (Clam

shell bucket) a Trench depth and width vary depending on depth to bedrock from CSR 2014

b Material calculations not inclusive of bedrock, volumes based on depth to bedrock data from CSR 2014

Depending on the method selected for excavation between -8 to -12, approximately 52,300 to 77,500m3 of in situ material is proposed to be trenched and sidecast for the installation of the two subsea cables. The volume of sidecast sediment was calculated based on the methods of excavation and the resulting trench dimensions. The clam shell bucket will require the trench to be excavated prior to the installation of the cable. This requires the trench to be excavated to a width greater than the cable diameter to account for potential infilling in the time between excavation and cable installation. The TROV will excavate the trench simultaneous to cable laying; this reduces the width of the trench opening required. The TROV will reduce the volume of sediment excavated in the New Brunswick nearshore environment between -8 and -12 m by approximately 25,200 m3.


Existing Conditions February 23, 2016

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2.0 EXISTING CONDITIONS

2.1 METHODS

A review of available oceanographic data and summary of meteorological and oceanographic conditions in the Northumberland Strait is summarized in the EIA (Stantec 2015a). The following sections summarize the methods used to establish baseline conditions to supplement the data presented in the EIA.

Field programs were completed to define model parameters such as bathymetry, currents, water quality and particle size of the in situ material in the Northumberland Strait, specifically in the nearshore environment. Existing sediment particle size data for Northumberland Strait sediments that was collected to inform the EIA (Stantec 2015a) was also used for the sediment transport modelling. A second component of the field program was conducted to determine the baseline sediment deposition rates in the area of the cables and the particle size of the natural deposition.

2.1.1 Current Profiling

Currents were measured in the Northumberland Strait using two types of Acoustic Doppler Current Profilers (ADCP). ADCPs measure water currents using sound transmitted into the water and the Doppler shift of the return signals. The ADCP works by transmitting ‘pings’ of sound at a constant velocity into the water. The sound waves reflect back from suspended material to the instrument. Due to the Doppler Effect, the reflected waves have a different frequency based on the speed of the suspended material in the water. The instrument uses the change in frequency to calculate the speed of the particle and thus the water. These pings are grouped into depth ranges or cells throughout the water column allowing for an instantaneous measurement of current velocity at multiple depths for that location and point in time.

Current profiling in the nearshore environment of the Northumberland Strait (less than12 m chart datum) was completed using a Teledyne-RDI River Ray. The RiverRay is a 600 Hz towable ADCP with a profiling range of 0.4 m to 60 m water depth and collects measurements every 10 to 30 cm in the water column, depending on water depth. Profiling for currents in the nearshore environment was completed between October 5 and 6, 2015. Currents were measured for three transects on both the PEI and NB coasts and during the flooding and ebbing tides.

Currents at water depths of greater than12 m were measured using a Teledyne-RDI Workhorse Sentinel. The Sentinel is a 300 Hz vessel mounted ADCP with a profiling range of 0.5 m to 110 m. Data were collected every 25 to 50 cm in the water column depending on the water depth, the greater the depth the greater the depth between measurements. Current measurements in the Northumberland Strait were completed on November 12, 2015 by conducting two crossings for the Strait, once during an ebbing tide and the second during a flooding tide.



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During the ADCP work, bathymetric data were collected simultaneous with the water current data, though these data are limited to the areas profiled for water currents including the two transects across the Northumberland Strait and the NB and PEI nearshore transects in the cable landing areas.

2.1.2 Water Column Total Suspended Solids, Water Quality and Sediment Particle Size

Twelve stations along the proposed cable route were selected to represent baseline conditions in the nearshore area. At each of the 12 stations (Figure 2.1) water samples were collected for the analysis of Total Suspended Solids (TSS), an in-situ water quality profile was conducted and sediment samples were collected for the analysis of particle size.

Water samples were collected from six PEI nearshore and six NB nearshore locations. At each station samples were collected below the surface (1 m), mid water column, and 1 m above the bottom. All samples were collected using a 5 L Niskin sampler washed prior to sampling and rinsed prior to the collection of a sample at each station. The samples were stored in 1 L opaque plastic bottles on ice for transportation and packaged in coolers for shipment to Maxxam Analytics of Bedford, NS for analysis.

Subsequent to sampling for TSS, at each sampling station a water quality profile was conducted using a YSI 6600 multi-parameter sonde. The sonde was calibrated prior to field use, with the dissolved oxygen sensor calibrated daily immediately prior to use. The parameters measured included depth, temperature, salinity, pH, dissolved oxygen and turbidity.

At each of 12 stations a sediment grab (Petite Ponar, 0.1 m2 surface area) was used to collect samples of the top 15 cm of sediment. This sediment was stored in glass jars on ice and packaged in coolers for shipment to Maxxam Analytics of Bedford, NS for analysis of particle size.

PENorthumberland Strait

NB

Water and Sediment Trap Sampling Locations

Figure 2.1121811475 - PEI-NB Interconnection - Maritime Electric Company, Limited




Sampling Location#I Sediment Trap "6 Water Quality and Sediment Station

Bathymetric Contour (m)Proposed Project Components

Proposed Transmission LineProposed Fence

Proposed Project Components in theNorthumberland Strait


Bathymetry, (m) Chart Datum0 - 55 - 1010 - 1515 - 2020 - 2525 - 3030 - 35

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2.1.3 Baseline Sediment Deposition

Baseline sediment deposition from the water column was measured using six sediment traps. Three sediment traps were deployed in both the PEI and New Brunswick nearshore environments (Figure 2.1). These sediment traps were constructed with a base, retrieval cables, a sediment collection tube, and a funnel-shaped opening to increase the surface area of sediment collection (Figure 2.2).

Figure 2.2 Sediment Trap Design

These traps were deployed on October 5 (PEI) and October 6 (New Brunswick) and retrieved on November 12 for a total of 38 days and 37 days of immersion, respectively. Sediment retrieved from inside the sediment traps were weighed then dried at ~15 °C for at least 24 hours or until cracks appeared in the sediment (USGS 2002). The dried sediment was weighed and a hydrometer test was performed based upon American Society for Testing and Materials standard (ASTM, 2007) to determine the fractions of sand, silt and clay.

Overall Height = 3.0 m

Opening Diameter = 0.105 m

Funnel opening

Sediment storage tube (0.05 m dia.)

Concrete base with anchor points



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2.2 RESULTS

2.2.1 Bathymetry

McGregor Geoscience conducted a Marine Geophysical Survey of the area for the Project in fall 2015 (McGregor 2015). As part of that program, bathymetric data were collected using a multi-beam sonar system (Reason 7125 200/400kHz Unit). The bathymetry used in this report is based on the Marine Geophysical Survey results (Appendix B Figure B.1).

The bathymetry along the cable corridor in the nearshore area of New Brunswick generally slopes gently towards the middle of Northumberland Strait. Slopes in this area range from 0° to 1°, with the exception of a ridge running northwest to southeast. This ridge rises up to 6 m above the surrounding seabed and is approximately 250 to 300 m wide; the slope along this ridge rises as high as 12º. The ridge decreases in height with distance to the southeast. The original route as shown in Figure 1.1 crossed over this ridge; alterations to this route show the route passing to the southeast and east of this ridge.

Sand waves are present running perpendicular to the ridge noted above; the largest sand waves are approximately 1m in height and separated by 25 to 50 m. These waves become smaller and more uniform around the perimeter of the ridge. Sand waves are generated by flow over the seabed and their crests are oriented perpendicular to the direction of current. The ridge where the sand waves are present can be considered to be oriented in the general direction of the currents.

Once past the ridge, water depths resume increasing to a well-developed channel where maximum water depths of 30 m are reached. The seabed rises out of the channel quickly to a water depth of 25 m, where the slope decreases and the seabed gradually rises to a water depth of 18 m. This seabed terrace at 18 m continues with water depths gradually decreasing to until approximately 1.5 km from the PEI shoreline where slopes increase ending at the shoreline at Borden-Carleton.



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2.2.2 Tides and Meteorological Conditions

Tides in the area of the Project were sourced from the DFO water level database (CHS 2015) for Port Borden, PEI and Cape Tormentine, NB. Tides range in Port Borden from 0.5 to 2.5 m chart datum (CD) during a spring tide to 1.1 to 2.2 m during a neap tide. Similar ranges (1.0 to 2.0 m and 0.4 to 2.4 m CD, respectively) were predicted for Cape Tormentine, NB.

The Northumberland Strait exhibits about two high tides and two low tides per day and the magnitude between these two tides differ in height (mixed semidiurnal). Since tidal wavelengths vary with depth, main currents in the Strait reverse themselves near the shore about one hour ahead of the main channel. Figure 2.3 illustrates the predicted mixed semidiurnal tides for the week of October 5, 2015 when the water current, water quality, and sediment particle size data were collected around Port Borden and Cape Tormentine.

Figure 2.3 Tide Levels at Port Borden and Cape Tormentine

Port Borden

Cape Tourmentine

Sampling Date PEI

Sampling Date NB



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Meteorological data were obtained at two locations: Maples Plains, PEI - Environment Canada Meteorological Station ID: 8305500 and Shediac, NB - Environment Canada Meteorological Station ID: 8100593. The following tables outline the average conditions observed at the representative locations during the field programs in October and November.

Table 2.1 Meteorological Data - PEI

Maple Plains, PE October 5, 2015 October 6,2015 November 12, 2015

Temperature (°C) 8.1 10.1 3.3

Average Wind Speed (km/h) 3.1 3.2 6.5

Average Wind Direction (°) 170 160 110

Table 2.2 Meteorological Data - NB

Maple Plains, PE October 5, 2015 October 6,2015 November 12, 2015

Temperature (°C) 9.2 9.6 5.1

Average Wind Speed (km/h) 5.3 4.6 7.0

Average Wind Direction (°) 190 190 100

2.2.3 Measured Currents

Water current data were collected in the PEI and NB nearshore environments using an ADCP on October 5 and 6, 2015 and at select locations within the Northumberland Strait on November 12, 2015. In the nearshore environment, three transects were conducted along the cable corridor perpendicular to the shoreline at Cape Tourmentine and Port Borden during both ebbing and flooding tides, resulting in six transects per location. Select data is presented to show surface (1 to 3 m) and bottom (1 to 3 m above the bottom) current magnitudes and direction for an ebbing tide and flooding tide in the nearshore environments.

At the New Brunswick landing site, where the Cape Tourmentine wharf provides shelter, surface currents were generally wind-driven with low magnitudes nearshore. Once outside the sheltered area of the wharf and breakwater, currents were generally directed towards the Strait with increasing current velocities observed with distance from the breakwater (Figure 2.4).

Figure 2.5 illustrates the variable current direction and low magnitude in the nearshore area surrounding the Cape Tourmentine breakwater (A1), followed by increasing current velocities in a steady southwest direction (B1), before a second decrease in speed and change in direction (A2), then a return to a southwest current direction. It appears the wharf is affecting current patterns during a flooding tide with currents during an ebbing tide generally flowing along the coastline from north to south.



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At the PEI landing site surface currents during a flooding tide were variable but generally towards shore, which reversed during an ebbing tide with currents heading predominately offshore, the bottom currents followed a similar pattern (Figure 2.6).

Generally the current direction at the time of the surveys appeared uniform from surface to bottom with current velocities higher at the surface than at bottom. Flooding tides appear to result in higher current velocities in the vicinity of the Project Area.

PE


NB

Current Velocities Measured in the Project Area - New Brunswick Nearshore

Figure 2.4

Area ofInterest





Surface Current Speed (m/s)

± < 0.1± 0.1 - 0.2± 0.2 - 0.3± 0.3 - 0.4± 0.4 - 0.5± > 0.5


Proposed Transmission LineProposed Project Components in theNorthumberland Strait



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NEW BRUNSWICK

CapeTormentine

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Chem

inOld Ferr

y Road

Route 955 Highway

High Tide + 4 hrs

Surface Ebbing

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Surface Flooding

Bottom Flooding Low Tide + 4 hrs




Cape Tormentine

Cape Tormentine Cape Tormentine

Cape Tormentine

Tidal

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tion

(m, c

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datu

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Time (M/D/T)

Tidal stage during current measurements

Oct. 5, 2015 14:24 Oct. 5, 2015 19:12 Oct. 6, 2015 00:00 Oct. 6, 2015 4:48 Oct. 6, 2015 9:36 Oct. 6, 2015 14:24 Oct. 6, 2015 19:120

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Oct. 7, 2015 0:00Oct. 5, 2015 19:12 Oct. 6, 2015 00:00 Oct. 6, 2015 4:48 Oct. 6, 2015 9:36 Oct. 6, 2015 14:24 Oct. 6, 2015 19:120

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16

Figure 2.5 Vertical Profile (Direction and Magnitude) of New Brunswick Nearshore Currents – Flooding Tide

A1 B1

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PE


NB

Current Velocities Measured in the Project Area - PEI Nearshore

Figure 2.6

Area ofInterest





Surface Current Speed (m/s)

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Proposed Transmission LineProposed Fence

Proposed Project Components in theNorthumberland Strait



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Borden

UV1

High Tide + 4.5 hrs

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Borden

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Oct. 4, 2015 19:12 Oct. 5, 2015 0:00 Oct. 5, 2015 4:48 Oct. 5, 2015 9:36 Oct. 5, 2015 14:24Oct. 4, 2015 14:24 Oct. 5, 2015 19:120

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Oct. 4, 2015 19:12 Oct. 5, 2015 0:00 Oct. 5, 2015 4:48 Oct. 5, 2015 9:36 Oct. 5, 2015 14:24 Oct. 5, 2015 19:12 Oct. 6, 2015 0:000

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18

2.2.4 Temperature, Salinity and Turbidity Data

Water quality profiles were collected on October 5, 2015 at six locations within the PEI nearshore environment and on October 6, 2015 at six locations within the New Brunswick nearshore environment. Water quality parameters collected included turbidity, dissolved oxygen, temperature and salinity. Turbidity, salinity and temperature were collected as parameters for inclusion in the sediment dispersion and transport modelling.

At the time of the data collection in the PEI nearshore environment no thermoclines or haloclines were observed and the water column did not appear stratified (Figure 2.7). Salinity measured at all sites was between 28.63 and 28.83 practical salinity units (psu) (mean = 28.80 psu), temperature was between 15.4 and 15.9 ºC (mean = 15.7 ºC), turbidity measured between 0.3 and 7.4 Nephelometric Turbidity Unit (NTU) (mean = 3.4 NTU).

Similarly in the New Brunswick nearshore environment no thermoclines or haloclines were observed and the water column did not appear stratified (Figure 2.8). Salinity measured at all sites was between 28.72 and 29.08 psu (mean = 28.8 psu), temperature was between 15.1 and 16.2 ºC (mean = 15.5 ºC) with turbidity measuring between 1.0 and 7.2 NTU (mean = 4.1 NTU).



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Figure 2.7 PEI Water Quality Profiles (October 2015)



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Figure 2.8 New Brunswick Water Quality Profiles (October 2015)



21

2.2.5 Total Suspended Sediments

At each of the water quality profiling stations, water samples were collected for TSS. The location of each sampling station is presented in Figure 2.1. Samples were collected at surface (1 to 3 m), mid water column (1/2 water depth) and 1 to 3 m off the bottom. The TSS results are presented in Table 2.3. TSS concentrations ranged between non-detect (<1.0mg/L) and 8.2 mg/L in the nearshore around Borden, PEI and between 1.0 and 4.6 mg/L in the nearshore of Cape Tourmentine, NB. Generally TSS values near bottom were higher than observed mid water column or at surface.

Table 2.3 Nearshore Baseline Total Suspended Sediment Concentrations

PEI Nearshore (October 5, 2015)

Sample Station PEI - 1 PEI - 2 PEI - 3 PEI - 4 PEI - 5 PEI - 6

Kilometre Post (KP) (km) 16.1 15.8 15.5 15.1 14.8 14.4

Coordinates (UTM NAD 83) 446704; 5121650

446534; 5121359

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TSS Concentrations (mg/L)

Surface 3.0 3.6 2.0 2.0 1.6 4.2

Mid 2.4 4.0 2.4 1.6 <1.0 2.6

Bottom 5.0 3.4 2.8 2.4 8.2 1.4

New Brunswick Nearshore (October 6, 2015)

Sample Station NB - 1 NB - 2 NB - 3 NB - 4 NB - 5 NB - 6

KP (km) 0.4 1.5 2.1 2.9 3.4 3.8

Coordinates (UTM NAD 83) 439897; 5108507

440822; 5108602

441202; 5109226

441447; 5110022

441518; 5110560

441536; 5110937

TSS Concentrations (mg/L)

Surface 3.4 2.8 1.2 1.0 1.0 2.4

Mid -a -b 1.4 2.6 -b -a

Bottom -a 4.6 3.2 3.0 <2.0 -a aSample Station Water Depth less than 5m, mid depth and bottom samples were not collected. bSample Station Water Depth less than 8 m mid depth sample was not collected.

2.2.6 Sediment Particle Size

Ten sediment samples were originally collected in October 2014 to inform the EIA, with two located at water depths of less than -12 m. Additional samples of sediment were collected on



22

October 5 and October 6, 2015 at the six stations where water samples and water quality profiles were collected. The collection of sediment along the Borden nearshore was difficult as rock was present at 4 of 7 sampling locations. Sediment was obtained by repeatedly sampling until a sufficient sample volume was obtained.

The sediment was predominantly sand with minor components of silt and clay (Table 2.4). Gravel was observed at fractions of between <0.1 and 5.8 % (Table 2.4).

Table 2.4 Particle Size Distribution for PEI Sediment Samples

Water Depth (m)

Gravel (>= 4.75mm)

(%)

Sand (<4.75mm and

>0.075 mm) (%)

Silt (<0.075mm and

>0.005 mm) (%)

Clay (<0.005mm)

(%)

D50 (mm)

PEI Station - 1 2 <0.1 78 16 6.5 0.091

PEI Station - 2 6 <0.1 96 0.8 2.7 0.168

PEI Station - 3 No Sample Collected

PEI Station - 4 12 <0.1 96 0.9 3.1 0.168

PEI Station - 5 13 <0.1 79 15 6.2 0.082

PEI Station - 6 14 0.5 96 0.9 2.3 0.178

S1a 9 5.8 71 16 7.4 0.126

aFrom PEI-New Brunswick Cable Interconnection Upgrade Project EIA (Stantec 2015a)

The New Brunswick sediment samples were predominantly sand with minor components of silt and clay. In three samples gravel was noted at fractions between <0.1 and 11%.

Table 2.5 Particle Size Distribution for New Brunswick Sediment Samples

Water Depth (m)

Gravel (>= 4.75mm)

(%)

Sand (< 4.75mm and

> 0.075 mm) (%)

Silt (< 0.075mm and

>0.005 mm) (%)

Clay (< 0.005mm)

(%)

D50 (mm)

NB Station - 1 2 <0.1 87 7.4 5.9 0.094

NB Station - 2 6 <0.1 97 0.7 2.5 0.330

NB Station - 3 8 8 87 1.6 3.4 0.220

NB Station - 4 9 <0.1 97 0.7 2.6 0.182

NB Station - 5 5 <0.1 98 0.4 1.3 0.310

NB Station - 6 9 2.1 96 0.2 1.5 0.320

S10a 7 11 79 5.4 4.8 0.290

aFrom PEI-New Brunswick Cable Interconnection Upgrade Project EIA (Stantec 2015a)



23

2.2.7 Sediment Trap Results

Sediment traps were deployed in October and retrieved in November 2015 with a monitoring period of 38 days for PEI and 37 days for NB. Of the six traps deployed five were retrieved, the sixth trap (PEI – ST1) was not located. PEI – ST1 was situated in an area where current velocities were similar to the areas of the five other traps and a search was completed in the immediate area.

The depth of sediment retained by the sediment trap and the trap measurements were used to determine a deposition rate per day (Table 2.6). The sediment collected was weighed and dried to determine deposition on a dry-weight basis. Deposition rates were between 0.4 and 0.5 mm per day over the immersion period. Deposition rates are likely elevated between October and November as compared to more calm periods in summer. During the deployment several gale warnings were in effect for the Northumberland Strait, indicating winds in excess of 62 km/h. These high wind events are more likely to transport sediment in the nearshore areas and increase deposition rates.

Table 2.6 Baseline Sediment Deposition Rates (Oct – Nov 2015)

Sediment Trap ID

Coordinates (NAD 83)

KP (km) Water Depth (m)

Sediment Depth (cm)

Wet Mass (g)

Dry Mass (g)

Sediment Volume /

Day (cm3/day)

Sediment Deposition

Rates (cm/day) X (m) Y (m)

PEI -ST1 446476 5120464 14.9 12 Missing

PEI -ST2 446179 5120487 14.9 13 10.4 99.18 79.32 4.35 0.05

PEI -ST3 446293 5120400 15.0 14 11.0 103.94 84.46 4.60 0.05

NB - ST1 441342 5110501 3.3 7 9.7 96.17 75.73 4.17 0.04

NB - ST2 441513 5110563 3.4 8 10.1 95.99 78.04 4.34 0.05

NB - ST3 441643 5110437 3.3 7 8.0 83.80 60.73 3.44 0.04

A hydrometer test was conducted on the dried sediment to determine the fractions of sand, clay and silt in the material. Density of the deposited material was calculated from the volume of sediment collected and the dry weight. The majority of the deposited material was in the silt fraction 67 to 75% (mean = 74%), with a lesser fraction of clay 20 to 21% (mean = 20%) and sand 6 to 12% (mean 7%).


Sediment Deposition Modelling February 23, 2016

24

3.0 SEDIMENT DEPOSITION MODELLING

3.1 APPROACH

Modelling was conducted to predict initial deposition in the nearshore environment of New Brunswick. The New Brunswick coast was selected because of sedimentation concerns raised by NB fishers, the distance offshore that trenching will be required in NB compared to PEI, and the seabed is uniformly composed of sand. Conversely, the nearshore environment for the PEI coast in the vicinity of the Project has a greater proportion of hard substrate such as rock, cobble and boulders, and limited overlying sediments (CSR 2015, McGregor 2015) which limits the sediment available for dispersal and transport.

On the New Brunswick side of the Strait in water shallower than -12 m, two types of trench excavation methods are proposed. In water depths from -2 to -8 m, excavation will take place using a clam shell bucket to excavate a 1 to 2.2 m deep and 2 to 9 m wide trench with slopes of approximately 2:1, resulting in a trench bottom width of 1 to 2 m. The exact dimensions of the trench will depend on the presence of bedrock if encountered.

From -8 to -12 m excavation will either continue with the clam shell bucket or alternatively a TROV may be used to produce the trench and lay the cable. The TROV will create a trench approximately 1.6 m deep and 0.35 m wide. The 1.3 to 2.2 m burial depth of the cable was determined as the recommended depth to reduce risk from ice scour in shallow waters (CSR 2014); at water depths greater than -12 m cable burial depth will decrease to 0.6 m below the seafloor.

The TROV works by side casting the sediment in the trench and allowing the cable to trail along behind the cutter head. Minor fractions such as silt and clay may be resuspended and enter the water column, while sand and gravel is predicted to settle within meters of the trench. Based on the smaller volume of sediment which will be resuspended with this trenching method, and the predominate sand composition for the Northumberland Strait in the submarine cable corridor, the sediment dispersion from the operation of the TROV was not modelled.

Trenching with a clam shell bucket will excavate more material and resuspend a greater volume of material. The clam shell bucket was modelled for sediment dispersion at water depths of -2 to -8 m. Initial estimates indicate trenching with the clam shell bucket will remove 11 m3 of material per metre of trench. The modelling scenario estimated the sediment deposition resulting from trenching a 100 m segment. The entire volume of sediment removed from the trench was included in the model (1,100 m3 per 100 m). For comparison, the TROV is anticipated to resuspend 77 m3 per 100 m of buried cable.



25

3.2 METHODS

Two sites were chosen for modelling in the New Brunswick nearshore environment to predict the initial sediment deposition from excavation and side casting. These two sites correspond to locations in which baseline sediment grain size, water column turbidity, TSS levels and water velocity measurements were collected in the field. The sites NB-1 and NB-3 (shown on Figure 2.1) correspond to water depths of approximately 3 and 8 m, respectively. NB-3 represents the area of potentially higher sediment dispersion as a result of the higher currents compared to the inshore site NB-1 in the area of the wharf and breakwater. Sediment dispersion with ebbing and flooding tides were modelled for both locations.

Initial sediment deposition was estimated using the US Army Corps of Engineers STFATE model (Short-Term FATE of dredged material disposal in open water) (Johnson et al., 1994). STFATE evaluates the short-term dispersion of sediments released from the disposal of sediment. The model was developed from the DIFID (disposal from an instantaneous discharge) model originally prepared by Koh and Chang (1973). The behavior of the material during disposal is assumed to be separated into three phases: convective descent (spreading through the water column during the fall to bottom); dynamic collapse (the result of the descending material impacting the bottom); and short-term passive transport-dispersion (the spreading of the sediment upon impacting the bottom, determined by ambient currents and turbulence).

3.2.1 Modelled Scenarios

Data for water current direction and magnitude were collected in the field for both an ebbing and flooding tide and are presented in Section 2.2.3. Though currents recorded during the flooding tide were observed to be higher than currents measured during the ebbing tide both currents were modelled, as there were variances in current direction. At site NB-3 an additional scenario was modelled with the inclusion of maximum predicted currents in the area. Surface currents of 113 cm/s (2.2 knots) were used, based on the predicted current velocities in the Abegweit Passage (CHS 2015a). This current speed is much higher than what was observed during the October surveys and is higher than that listed on the Northumberland Strait Navigation Chart (CHS 2015b) of 103 cm/s (2 knots).

Tables 3.1 and 3.2 list sediment characteristics and current values for the two locations modelled.



26

Table 3.1 New Brunswick Nearshore Model Inputs – Ebbing Tide

Station ID

Coordinates (NAD 83 Z20T) KP

(Km)

Water Depth

(m)

Average Current Velocity (cm/s)

Average Current

Direction (°)

Sediment Grain Size

(%) Easting (m)

Northing (m)

NB-1 Ebb 439902 5108504 0.4 3.4 Sur. = 3.2 Bot. = 2.2

Sur. = 50 Bot. = 44

87% Sand 7% Silt

6% Clay

NB-3 Ebb 441197 5109235 2.1 8.0 Sur. = 7.4 Bot. = 6.9

Sur. = 208 Bot. = 191

8% Gravel 87% Sand

2% Silt 3% Clay

NB-3 Ebb Peak

Currents 441197 5109235 2.1 8.0 Sur. = 113

Bot. = 85 Sur. = 208 Bot. = 191

8% Gravel 87% Sand

2% Silt 3% Clay

Table 3.2 New Brunswick Nearshore Model Inputs – Flooding Tide

Station ID


(Km)

Water Depth

(m)


Average Current

Direction (°)

Sediment Grain Size

(%) Easting (m)

Northing (m)

NB-1 Flood 439902 5108504 0.4 3.4 Sur. = 4.6 Bot. = 4.9

Sur. = 28 Bot. = 20

87% Sand 7% Silt

6% Clay

NB-3 Flood 441197 5109235 2.1 8.0 Sur. = 9.6 Bot. = 7.7

Sur. = 224 Bot. = 168

8% Gravel 87% Sand

2% Silt 3% Clay

NB-3 Flood Peak

Currents 441197 5109235 2.1 8.0 Sur. = 113

Bot. = 85 Sur. = 224 Bot. = 168

8% Gravel 87% Sand

2% Silt 3% Clay



27

3.3 RESULTS

Cape Tormentine, NB Inshore Excavation Area (Site NB-1)

Sediment deposition was modelled based on excavation and side casting of material during flooding and ebbing tides for a water depth of 3 m at site NB-1. The results of the STFATE model for each tide are presented in Figure 3.1. In both cases the majority of the sediment would deposit within 75 m of side casting and create a mound approximately 0.5 m high at the sidecasting site. The extent of the sediment dispersion figures are bounded by the area where a 1 mm thick layer would deposit as a result of the side casting operations, with a thick line outlining the 10 mm thick layer. The results from modelling indicate that the stronger currents measured during the flooding tide would disperse the finer sediment fraction further out towards the northeast. This 1 mm layer is predicted to extend up to 300 m from the excavation area during a flooding tide. The majority of the sediment fell out of suspension within 2 hours post-excavation with 98% of the material settling to the seafloor during an ebbing tide and 99% of the material settling during a flooding tide. The remaining material in suspension would consist of silt and clay and form the basis for the plume discussed in Section 4.0.

PredictedSedimentDeposition

(m)

DominantCurrent Dominant

Current



29

Cape Tormentine, NB Offshore Excavation Area (Site NB-3)

Sediment deposition was also modelled for the excavation and side casting of material from the trench at a water depth of 8 m during an ebbing tide and flooding tide. Figure 3.2 illustrates the results of the STFATE model for site NB-3. The zone of deposition occupies a smaller area compared to the inshore results for site NB-1. The silt and clay components in the sediment sampled for site NB-3 were lower, indicating a larger average particle size and therefore resulting in less dispersion as predicted by the model, even though the currents are higher offshore, it did not result in a larger area for sediment deposition. The modelling results indicate that deposition thickness will approach 0.6 m at the location of side casting with the largest volume of the sediment deposited within 60 m. The extent of sediment dispersion was modelled to determine a 1 mm depositional layer, with a thick line outlining the 10 mm thick layer. The 1 mm layer is predicted to be limited to an area within 80 m of the excavation with the 10 mm layer occurring within 60 m of the excavation site. Based on the modelling results, 98% of the sediment excavated will settle to the seafloor within 2 hours for an ebbing tide and 99% within 2 hours for a flooding tide. The remaining material in suspension will consist of silts and clays.

The worst-case scenario was modelled for the maximum surface current listed from Abegweit Passage (Northumberland Strait) current tables (CHS 2015a) of 113 cm/s (or 2.2knots). The sediment dispersion for the maximum predicted currents was modelled only for site NB-3 as this is the furthest extent for offshore excavation using a clam shell bucket. Site NB-1, located further inshore, is unlikely to experience these higher currents because of the wharf and breakwater and therefore was not modelled. Bottom currents of 85 cm/s were estimated based on the surface current predictions of 113 cm/s and the relationship between surface and bottom currents identified during the ADCP surveys. The predicted results for sediment dispersion using maximum currents are presented in Figure 3.3. The modelling results indicate that deposition thickness will approach 0.3 m at the location of side casting with the majority of the sediment deposited within 110 m. The extent of sediment dispersion was modelled to determine a 1 mm and 10 mm depositional layer. Under maximum predicted currents this 1 mm layer is predicted to extend up to 950 m from the excavation site, with the 10 mm layer extending up to 250 m from the excavation site. Based on the modelling results, 96% of the sediment excavated will settle to the seafloor within 2 hours for both an ebbing tide and flooding tide. The remaining material in suspension will consist of silts and clays.


(m)

DominantCurrent Dominant

Current


(m)

DominantCurrent

DominantCurrent



32

3.4 EXTENT OF SEDIMENT DEPOSITION

Excavation of the trench for the installation of the subsea power cables will result in the resuspension of sediment. Baseline sediment deposition rates in the New Brunswick nearshore environment were measured to be between 0.4 and 0.5 mm per day in the period from October to November. Increasing the deposition of sediment on the seafloor has the potential to induce mortality, reduce growth of some benthic species, reduce larval settlement, and change fauna composition amongst benthic organisms (Neff et al. 2004). At thicknesses of approximately 10 mm or more, benthic communities comprised of sedentary or slow moving species may be smothered and the sediment quality will be altered in terms of nutrient enrichment and oxygen depletion (Neff et al. 2000; Neff et al. 2004). This 10 mm threshold level was used to determine the extent of potential interactions between the Project and the marine benthic environment. Table 3.3 lists the distance from the release of sediment (i.e., site of deposition with the clam shell bucket) to the outer margin of the 10 mm deposition layer for the various modelling scenarios conducted.

Table 3.3 Distance to Outer Boundary of the 10 mm Deposition Layer

Station ID Water Depth

(m)


Average Current

Direction (°)

Distance from trench to 10 mm

Deposition

NB-1 Ebb 3.4 Sur. = 3.2 Bot. = 2.2

Sur. = 50 Bot. = 44 60 m

NB-1 Flood 3.4 Sur. = 4.6 Bot. = 4.9

Sur. = 28 Bot. = 20 75 m

NB-3 Ebb 8.0 Sur. = 7.4 Bot. = 6.9

Sur. = 208 Bot. = 191 55 m

NB-3 Flood 8.0 Sur. = 9.6 Bot. = 7.7

Sur. = 224 Bot. = 168 60 m

NB-3 Ebb

peak currents 8.0 Sur. = 113

Bot. = 85 Sur. = 208 Bot. = 191 110 m

NB-3 Flood

peak currents 8.0 Sur. = 113

Bot. = 85 Sur. = 224 Bot. = 183 250 m1

1Patches of sediment deposition extend out from the trench up to 330 m

The results of the sediment dispersion model indicate that under typical tidal currents the coarse sand and gravel components of the side cast material will settle within 20 minutes of release; under peak tidal currents this value increases to approximately 40 minutes. Smaller particles such as silts and clays take much longer to settle and under typical current conditions did not completely settle within 2 hours of release. The proportion of fine sediment remaining in suspension was low compared to the total material deposited. Under typical current conditions



33

98 to 99% of all sediment released settled to the seafloor within 2 hours. A similar trend was noted using the predicted maximum currents, with 96% of the total material settling within 2 hours and the remaining 4% consisting of almost equal proportions of silt and clay still in suspension.


Sediment Plume Modelling February 23, 2016

34

4.0 SEDIMENT PLUME MODELLING

4.1 APPROACH

Plume dispersion modelling was conducted with a similar approach used for modelling the initial sediment deposition modelling in the nearshore environment of New Brunswick. The plume modelling was conducted to predict the extent of the TSS concentrations as a result of clam shell bucket excavation operations and determine the distance until TSS concentrations decreased to threshold or baseline levels.

4.2 METHODS

Under typical dredging operations where the material is removed from the seafloor and brought to surface, the turbidity generated in the water column is the result of the resuspension of sediment from the excavation. For this Project and trenching to install the cable, the bulk of the sediment resuspension would result from side casting of the material after excavation, not the act of excavation itself (Hayes et al. 2007). The extent of the sediment plume is dependent on the type and amount of material excavated and the current velocity. The plume extent was modelled out to background concentrations measured for sites NB-1 and NB-3. For site NB-3 an additional scenario was modelled utilizing the maximum predicted currents in the area (CHS 2015a).

Plume dimensions and concentrations were estimated using the US Army Corps of Engineers STFATE model (Short-Term Fate of dredged material disposal in open water) (Johnson et al., 1994).


Current direction and magnitude data were collected for both an ebbing and flooding tide and are presented in Section 2.2.3. Currents recorded during the flooding tide were observed to be higher than currents measured during the ebbing tide at both locations; therefore, plume modelling was only undertaken for flooding tides. Similar to the sediment deposition modelling, the worst-case scenario (113 cm/s currents) from the predicted current tables (CHS 2015a). Table 4.1 lists the inputs used to characterize the two modelling locations.



35

Table 4.1 Water Column Turbidity Modelling Inputs

Station ID


(Km)

Water Depth

(m)

Background TSS Conc.

(mg/L)


Average Current

Direction (°)

Sediment Grain Size

(%) Easting (m)

Northing (m)

NB-1 Flood 439902 5108504 0.4 3.4 Sur. = 3.4 Bot. = N/A

Sur. = 4.6 Bot. = 4.9

Sur. = 28 Bot. = 20

87% Sand 7% Silt

6% Clay

NB-3 Flood 441197 5109235 2.1 8.0 Sur. = 1.4 Bot. = 3.2

Sur. = 9.6 Bot. = 7.7

Sur. = 224 Bot. = 168

8% Gravel 87% Sand

2% Silt 3% Clay

NB-3 Flood peak

currents 441197 5109235 2.1 8.0 Sur. = 1.4

Bot. = 3.2 Sur. = 113 Bot. = 85

Sur. = 224 Bot. = 168

8% Gravel 87% Sand

2% Silt 3% Clay

4.3 RESULTS

Under low current conditions such as the currents measured during the baseline field work the sediment plume will resemble a round cloud around the area of deposition. Under higher current conditions such as those modelled at NB-3, the plume is expected to form an elongated stream with little vertical rising (Figures A.1, A.2 and A.3, Appendix A). Predicted TSS values within 10 m (1 model cell) of the disposal area were estimated using the model but are included as an order of magnitude estimate, due to the highly variable nature of TSS concentrations in close proximity to side casting. The water column turbidity results were compared against the CCME Water Quality Guidelines for the Protection of Aquatic Life (CCME PAL) as a benchmark for potential effects to fish from TSS. The guideline recommends a maximum increase of 5 mg/L above baseline concentrations for long term (24 hr. – 30d) exposure. Table 4.2 lists the maximum predicted TSS concentration within the plume, the approximate distance at which the TSS concentration reaches 5 mg/L above baseline value and the approximate distance at which the TSS concentrations reach baseline. Figures showing a vertical profile along the longest axis of the plume, which is normally aligned with the dominant current, are presented in Appendix A.



36

Table 4.2 Summary of Water Column Turbidity Results

Station ID Water Depth

(m)


Average Current

Direction (°)

Maximum Predicted TSS Concentration

25 m from disposal (mg/L)

Distance to 5 mg/L above

baseline (m)

Distance to Baseline TSS

Concentrations (m)

NB-1 Flood 3.4 Sur. = 4.6 Bot. = 4.9

Sur. = 28 Bot. = 20

Sur. = 779 Bot. = 940

Sur. = 250 Bot. = 260

Sur. = 280 Bot. = 280

NB-3 Flood 8.0 Sur. = 9.6 Bot. = 7.7

Sur. = 224 Bot. = 168

Sur. = 306 Bot. = 660

Sur. = 170 Bot. = 240

Sur. = 220 Bot. = 260

NB-3 Flood Peak

Currents

8.0 Sur. = 113 Bot. = 85

Sur. = 224 Bot. = 183

Sur. = 380 Bot. = 545

Sur. = 200 Bot. = 250

Sur. = 240 Bot. = 280

4.4 SEDIMENT PLUME EXTENTS

The predicted TSS values estimated for the plume represent continuous concentrations that will be released during the excavation of the trench by a clam shell bucket. TSS concentrations in the shallow sections of the Northumberland Strait (less than -3m) of the excavation are predicted to be fairly constant within the water column. In deeper sections the TSS concentrations will be highest near bottom with lower TSS concentrations near surface.

Trenching operations are expected to occur over a period of days within the New Brunswick nearshore environment. The predicted concentrations were compared to the CCME Water Quality Guidelines for the Protection of Aquatic Life (CCME PAL). The CCME have outlined short-term (less than 24 hr.) and long-term (24 hr. to 30 day) guidelines for the protection of marine aquatic life. The long-term guideline value is defined as a maximum increase of 5 mg/L over the baseline concentrations, whereas the short-term guideline is a maximum increase of 25 mg/L over baseline. The baseline TSS concentrations for the project area ranged from non-detect (<1.0 mg/L) to 8.4 mg/L with a mean of 3 mg/L. Interpretation of the CCME guidelines would indicate a long-term TSS guideline value of 8 mg/L for the Northumberland Strait in the vicinity of the Project, with a short-term guideline value of 28 mg/L. The modelling results predict that water quality will be below the long-term TSS guideline value at distances greater than 280 m from the excavation site during typical tidal conditions and greater than 300 m during periods with high tidal currents.


Sediment Transport February 23, 2016

37

5.0 SEDIMENT TRANSPORT

5.1 APPROACH

Excavations of soft bottoms in the marine environment will infill naturally over time based on the movement of the seabed (bedload transport) and deposition from naturally occurring suspended sediment and from re-suspended bottom sediments. To decrease the time the trenches remain open Maritime Electric’s subcontractor will infill trenches in areas where the clam shell bucket or excavator will be used. For areas where the TROV will be used this is not feasible and the trench will be left to infill naturally. To estimate the time required to infill the trench, a sediment transport model (Sedtrans05) was used to calculate total bedload transport per hour per metre of trench. Using the assumptions that the majority of the trench would be approximately 0.6 m deep and 0.35 m in width and the volume required to infill this trench would come entirely from sediment transport (i.e., no slumping of the trench wall), the time to infill was determined on the basis of predicted sediment transport rates.

5.2 METHODS

To determine the rate of infilling along the open trench for the cable from approx. -12 m on the NB side to -12 m on the PEI side, Sedtrans05 was used to calculate bottom shear stresses and resulting bed load movement. Sedtrans05 is a sediment transport model for continental shelf and estuaries developed at the School of Ocean and Earth Science, Southampton Oceanographic Centre, University of Southampton, and the Istituto di Scienze Marine - Consiglio Nazionale delle Ricerche Venice. The model is described in Neumeier et al. (2008). It predicts the sediment transport at one location as a function of water depth, average sediment particle size, current velocity and waves (single-point model). Five different transport equations are available for non-cohesive sediments (sand) and one algorithm for cohesive sediment (mud). Sediment transport for Northumberland Strait was calculated using the non-cohesive equations.


Eight locations were selected to be modelled for the Northumberland Strait with a range of water depths from -12 m to -30 m. These locations correspond to stations where sediment was collected for chemical and physical analysis for inclusion in the EIA (Stantec 2015a) and where current and bathymetry data are available from the November 2015 ADCP survey.

Currents recorded during the flooding tide were observed to be stronger than currents measured during the ebbing tide in the deeper portions of the Northumberland Strait. Weaker currents result in reduced shear stress and decreased sediment transport (i.e., longer infilling times). Sediment transport rates resulting from the lower ebbing currents were modelled as a conservative worst-case scenario. An additional modelling scenario was conducted for all stations using the maximum surface current predicted for Abegweit Passage (2016 Current



38

Tables, CHS 2015). The bottom current was derived from the maximum surface current of 113 cm/s (or 2.2 knots), similar to the approach taken for modelling the maximum sediment dispersion and sediment plume dispersion. For wave action, the mean wave height and period for October was calculated from 60 years of MSC50 data using the nearest grid point (No. 009946). The characteristics of the stations modelled are provided in Table 5.1along with select model inputs.

Table 5.1 Sediment Transport Modelling Inputs

Sediment Transport Stationa

Coordinates (NAD 83) KP

(Km)

Water Depth

(m)

Bottom Current Velocity (cm/s)b

Particle Size (%) Average Grain Size

(D50) (mm)

Easting (m)

Northing (m) Gravel Sand Silt Clay

S8 441821 5111396 4.4 13.9 44 15 77 3 5 0.32

S7 442192 5112513 5.6 19.4 46 8 81 5 6 0.31

S6 442564 5113626 6.8 27.6 36 10 85 2 5 0.37

S5 443014 5115010 8.3 25.7 33 34 54 5 7 0.42

S4 443510 5116505 9.9 23.5 24 19 71 5 5 0.34

S3 445006 5117524 11.6 23.1 23 28 65 3 4 0.34

S2 446101 5119487 14.0 16.4 15 11 80 4 6 0.34 a Sediment Stations from Stantec 2015a bAverage current velocity 1 to 3 m from bottom

5.3 SEDIMENT TRANSPORT RATES

Sediment transport rates vary with the forces applied on the seafloor (i.e., currents and wave action) and the sediment composition. The smaller the sediment particle size the less force that is required to transport it. Sediment transport rates are presented in Table 5.2 as the resulting volume of sediment moved per hour per linear metre of trench. The sediment transport rates are listed for each station using the baseline currents and the maximum predicted currents from the Abegweit Passage Current Tables (CHS 2015).

The results indicate that using the baseline current conditions observed in November 2015, measureable sediment transport occurs in all but the deeper portion of the channel (KP 6 to KP12 where water depths are greater than 23 m). Incorporating the maximum predicted current, sediment transport is predicted to occur along the entire trench (Table 5.2).



39

Table 5.2 Sediment Transport Rates

Sediment Transport Station

Coordinates (NAD 83) KP

(Km)

Water Depth

(m)

Baseline Currents (Nov.

2015)A,B

Max Predicted CurrentsB,C

Sediment Transport (m3/hr/m)

Sediment Transport (m3/hr/m)

Easting (m)

Northing (m)

S8 441821 5111396 4.4 13.9 0.0047 0.0409

S7 442192 5112513 5.6 19.4 0.0079 0.0730

S6 442564 5113626 6.8 27.6 <0.0004 0.0449

S5 443014 5115010 8.3 25.7 <0.0004 0.0384

S4 443510 5116505 9.9 23.5 <0.0004 0.0564

S3 445006 5117524 11.6 23.1 <0.0004 0.0571

S2 446101 5119487 14 16.4 0.0018 0.0707 ABaseline currents collected during a flooding tide between Borden and Cape Tourmentine B Wave height and period taken from MSC50 Averages for October (Grid Point 009946) C Maximum predicted currents from Abegweit Passage Current Charts (CHS 2015)

5.4 TRENCH INFILLING

The sediment transport values from the Sedtrans05 model and the volume of the trench were used to estimate the time to infill the trench where excavation occurs using the TROV. The sediment transport rates were used to estimate the time to infill the trench under baseline and maxiumum current conditions, with the expectation that the time to infill would occur between these two scenarios. The trench infilling time was not estimated where the excavation will occur using the clam shell bucket or excavator. At these locations the sidecast material will be reused to infill the trench following cable installation.

Using the bedload transport rates to estimate sediment transport, the TROV trench (0.35 m x 0.60 m) is estimated to infill within 3 to 6 hours under sustained maximum currents. For baseline conditions, portions of the trench would infill within 1 to 5 days with sustained tidal currents, whereas in the deeper sections no bedload transport and a time to infill was not calculated (Table 5.2). The 3 to 6-hour estimate based on the maximum predicted currents is unreasonable as it would require the maximum currents to be sustained over a 3 to 6 hour period. These maximum currents are predicted to occur monthly during the larger spring tide for duration of approximately 1 hour each day over a period of 1 to 2 days (CHS 2015). Using a combination of the maximum predicted tides and the baseline current measurements it is anticipated, that the actual period for infilling of the trench would occur within days to weeks along the majority of the route. In areas where bedload movement is not predicted to occur under baseline conditions, infilling is predicted due to slumping of the excavated trench, monthly variance in



40

tidal currents, suspended sediment deposition, and increased current velocities induced by storm events. Infilling in these sections of the trench is likely to occur within weeks to months after excavation.

These results are comparable to the findings in the 2014 Marine Geophysical Survey Report (CSR 2015) which assessed ice scour (the trenches left by ice movement) within the Northumberland Strait. The report indicated that 75% of ice scour in sandy substrate was completely removed within 6 months and two thirds of the ice scour in gravel substrate were either severely infilled or completely removed in the same period of time (CSR 2015).


Summary February 23, 2016

41

6.0 SUMMARY

In an effort to reduce the effects on the marine environment from habitat alteration and sediment dispersion Maritime Electric has revised the cable route and installation methods. The realignment of the cable route in the shallow-water section will shift the cable footprint to the edge of the eelgrass habitat to avoid the high-density areas and allow the TROV to trench closer to shore. The use of the TROV will decrease the size of the trench required and limit the resuspension of sediment as compared to the clam shell bucket.

The results of the sediment dispersion modelling indicate that under typical tidal currents the coarse sand and gravel components of the sidecast material will settle within 20 to 40 minutes of release. Smaller particles such as silts and clays take much longer to settle and under typical current conditions did not completely settle within 2 hours of release. A 10 mm threshold level for deposition thickness was used to determine the extent of potential interactions between the Project and the marine benthic environment. The extent of the10 mm layer is predicted to occur within 75 m of the excavation using typical currents and up to 250 m when transported by higher tidal currents.

The predicted TSS values estimated for the plume represent continuous concentrations that will be released during the excavation of the trench by a clam shell bucket. TSS concentrations in the shallow excavation sections of the Northumberland Strait (less than -3 m) are predicted to be fairly uniform within the water column. In deeper sections the TSS concentrations will be highest near bottom with decreasing TSS concentrations near surface.

The sediment plume modelling results predict that water quality will be below CCME’s long-term TSS guideline value at distances greater than 280 m from the excavation site during typical tidal conditions and greater than 300 m during periods with high tidal currents.

Predictions on the time to infill the trench created by the TROV across the Northumberland Strait was completed using a sediment transport model (SedTrans05). Using a combination of the maximum predicted tides and the baseline current measurements it is anticipated that the actual period for infilling of the trench would occur within days along the majority of the route. In areas where bedload movement is not predicted to occur under baseline conditions, infilling is predicted due to slumping of the excavated trench, maximum currents induced by large spring tides, suspended sediment deposition, and increased current velocities induced by storm events. Infilling in these sections of the trench is likely to occur within weeks to months of excavation.


Limitations February 23, 2016

42

7.0 LIMITATIONS

To evaluate sediment dispersion associated with the proposed Project, particularly for trenching with a clam shell bucket, Stantec used a numerical modelling approach. Site-specific field measurements were used to input values into the numerical model and for verification purposes. The modelling results provide a basis for the evaluation of TSS plumes and bottom sediment accumulation associated with side casting. It is widely accepted that sediment transport modelling involves an inherent degree of uncertainty. In the models used (STFATE and SedTrans05) the primary sources of uncertainty are data related on bottom currents over complete tidal cycles and the inability to accurately predict the oceanographic conditions at the time of construction.

The following limitations must be considered when using the results presented in this section:

The modelling approach was based on an assumed excavation design. When theexcavation plan varies significantly from the assumed design, the predicted plumeextent and TSS concentrations may vary;

There are uncertainties associated with estimating settling velocities, critical shearstress/velocity for erosion, and sediment characterization in the study area;

The predicted TSS concentrations are based on model parameters such as settlingvelocity, critical shear stress/velocity for erosion, characterization of bottom sedimentsand hydrodynamic conditions in the study area;

The model has assumed a typical seabed sediment grading based on the availableinformation. However, the seabed sediment grading is likely to vary spatially; therefore,the type and rate of fine sediment release will also vary in time as the excavationlocation changes.


Closure February 23, 2016

43

8.0 CLOSURE

We trust this report contains information to supplement the PEI-NB Cable Interconnection Upgrade Project Environmental Impact Assessment and addresses the majority of marine environment information requests submitted by the New Brunswick Technical Review Committee.

Stantec Consulting Ltd. appreciates the opportunity to work with Maritime Electric on this Project. This document and the information contained within it is proprietary to Stantec, and shall not be reproduced or transferred to other documents, or disclosed to others, or used for any purpose other than that for which it is furnished without prior written permission of Stantec.

The conclusions are based on professional judgement based on the knowledge and information available at the time. The data, interpretations, recommendations and opinions expressed in this document pertain to this specific project, site conditions, project objectives, development and purpose described to Stantec by Maritime Electric and its contractors, and are not applicable to other project sites or locations.


References February 23, 2016

44

9.0 REFERENCES

ASTM D422-63(2007)e2, Standard Test Method for Particle-Size Analysis of Soils (Withdrawn 2016), ASTM International, West Conshohocken, PA, 2007, www.astm.org

Canadian Council of Ministers of the Environment. 1999. Canadian water quality guidelines for the protection of aquatic life. In: Canadian environmental quality guidelines, 1999, Canadian Council of Ministers of the Environment, Winnipeg

Canadian Hydrographic Service. 2015a. Tides. Accessed on: February 2, 2016 at: www.waterlevels.gc.ca

Canadian Hydrographic Service. 2015b. Tides. Accessed on: February 2, 2016 at: www.waterlevels.gc.ca

Canadian Hydrographic Service. 2013. Tryon Shoals to Cape Egmont. Chart 4406.

Hayes, D. F., Borrowman, T. D., and Schroeder, P R. 2007. "Process-Based Estimation of Sediment Resuspension Losses During Bucket Dredging" Proceedings, XVIII World Dredging Congress 2007, WEDA, Lake Buena Vista, Florida, USA.)

Johnson, B. H., D.N. McComas, D.C. McVan and M.J. Trawle. 1994. Development and verification of numerical models for predicting the initial fate of dredged material disposed in open water. Report 1, Physical model tests of dredged material disposal from a split-hull barge and a multiple bin vessel. Draft Technical Report, U.S. Army Engineer WaterwaysExperiment Station, Vicksburg, MS

Koh, R.C.Y. and Y.C. Chang. 1973. Mathematical model for barged ocean disposal of waste. Environmental Protection Technology Series EPA 660/2-73-029, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.

McGregor Geoscience Limited. 2015. Subsea Cable Survey and Geotechnical Report R/V Strait Hunter and M/V Strait Sounder NB-PEI Interconnector Northumberland Strait, Canada.

Nafe, J.B., C.L. Drake. 1977. Physical Properties of Marine Sediments. Technical Report No. 2 CU-3-61 NObsr 85077 Geology.

National Oceanic and Atmospheric Administration. 2015. 2015 Atlantic Hurricane Season: Summary Data. Accessed at: http://www.nhc.noaa.gov/data/tcr/ Accessed on: January 29, 2016.


References February 23, 2016

45

Neff, J.M., Kjeilen-Eilersten, G., Trannum, H., Jak, R., Smit, M., Durell, G. 2004. Literature Report on Burial: Derivation of PNEC as Component in the MEMW Model Tool. ERMS Report No. 9B. AM 2004/024. 25pp.

Neff, J.M., McKelvie, S., Ayers, Jr., R.C. 2000. Environmental Impacts of Synthetic Based Drilling Fluids. OCS Study MMS 2000-64. US Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Program, New Orleans, LA. 118pp.

Neumeier U., Ferrarin C., Amos C.L., Umgiesser G. & Li M.Z. (2008) Sedtrans05: An improved sediment-transport model for continental shelves and coastal waters with a new algorithm for cohesive sediments. Computer & Geosciences. doi:10.1016/j.cageo.2008.02.007

Tenzer, R. and V. Gladkikh, “Assessment of Density Variations of Marine Sediments with Ocean and Sediment Depths,” The Scientific World Journal, vol. 2014, Article ID 823296, 9 pages, 2014. doi:10.1155/2014/82329

Sabol, B. M., R. E. Melton, R. Chamberlain, P. Doering & K. Haunert, 2002. Evaluation of a digital echo sounder system for detection of submersed aquatic vegetation. Estuaries 25: 133–141.

Schafer, C.T., J.N. Smith. 1999. Sedimentation, bioturbation, and Hg uptake in the sediments of the estuary and Gulf of St. Lawrence. Limnol. Oceanogr. 44(1), 1999, 207-219.

Stantec. 2015a. PEI-NB Cable Interconnection Upgrade Project Environmental Impact Assessment.

Stantec 2015b. PEI-NB Cable Interconnection Upgrade Project Environmental Impact Assessment Marine Supplemental Report No. 1

United States Geological Survey. 2002. Geochemical Sediment Analysis Procedures, Open File Report 02-371.

APPENDICES


February 23, 2016

APPENDIX A

Marine Geophysical Survey – Bathymetry

Survey Area - Northumberland StraitCape Tormentine NS to Borden-Carleton PEI

Marine Survey

!

!

!

!

!

!

!

!

!

!

!

!

1

2

3

4

5

6

1

2

3

4

5

6

-9

-18 -20

-20

-21-22-23-24

-26

-27

-28-29

-18

-19

-25

-7-8

-9

-11-12

-13

-6

-9

-3

-4

-5

-6

-7

-8

-14

-16

-13

-15

-17

-12

-9

-1-2

-20

-9

-9

-9

-18

-6

-9

-4

-14

-4

-5

-11

-10

-8

-8

-9

-9

-3

-9

-9

63°44'0"W63°45'0"W

63°46'0"W63°47'0"W

46°1

0'0"

N

46°1

0'0"

N

46°9

'0"N

46°9

'0"N

46°8

'0"N

46°8

'0"N

46°7

'0"N

63°4

4'0"

W63

°45'

0"W

63°4

6'0"

W63

°47'

0"W

46°7'0"N

4400

00

440000

4410

00

441000

442000

4420

00

443000

4430

00

5108

000

5108

000

5109

000

5109

000

5110

000

5110

000

5111

000

5111

000

5112

000

5112

000

5113

000

5113

000

°

!

!

!

!

!

!

!

!

!

!

!

!

!

!

6

7

8

9

10

11

12

6

7

8

9

10

11

12

-30

-18-18

-19

-20

-19

-20

-21-22-23

-25-26

-27

-28

-30-31

-24

-25-26-27

-28-30

-21

-22-23-2

4-2

5-2

6

-31

-19-20-21-22

-30-29

-24

-20

-17

-18

-18 -20

-22

-29

-29

-24

-21

-18

-23

-24

-25-26

63°43'0"W

63°45'0"W

46°1

3'0"

N46

°12'

0"N

46°1

2'0"

N

46°1

1'0"

N

46°1

1'0"

N46

°10'

0"N

63°4

3'0"

W63

°44'

0"W

63°4

4'0"

W63

°45'

0"W

46°13'0"N

46°10'0"N

4420

00

442000

4430

00

443000

444000

4440

00

445000

4450

00

5113

000

5113

000

5114

000

5114

000

5115

000

5115

000

5116

000

5116

000

5117

000

5118

000

5118

000

°

!

!

!

!

!

!

!

!

!

!

!

!

11

12

13

14

15

16

11

12

13

14

15

16

-4

-14

-17

-9

-19

-5

-18

-11

-17

-18

-16

-1-2-3

-5

-6

-8

-9

-4

-7

-12

-14-15

-19-21

-10

-11-13

-16-17

-18

-23-24-2

5

-25

-21

-14

-15

-4-6

-22

-24-2

2

-22

-14

-20

-8

-5

-4

-23

-24

-14

63°41'0"W

63°43'0"W

46°1

5'0"

N

46°1

5'0"

N

46°1

4'0"

N

46°1

4'0"

N

46°1

3'0"

N

46°1

3'0"

N46

°12'

0"N

63°4

2'0"

W

63°4

2'0"

W63

°43'

0"W

46°12'0"N

4440

00

444000

4450

00

445000

4460

00

4460

00

447000

4470

00

448000

4480

00

5117

000

5117

000

5118

000

5118

000

5119

000

5119

000

5120

000

5120

000

5121

000

5121

000

5122

000

5122

000

°

LS Cable

Multibeam - Bathymetry

McGregor Project No.: 1523

Date Saved: 12/08/2015 11:29:22 AM

A.1Filename: E_6.1_MultibeamBathymetry

R1

! KP

RPL

Depth Contours

Depth (m)High : 0

Low : -32

McGregor GeoScience Ltd.Bedford, Nova Scotia, Canada

63° W

63° W

63.5° W

63.5° W

64° W

64° W

64.5° W

64.5° W

46.5

° N

46.5

° N

46° N

46° N

400000

400000

450000

450000

500000

500000

5100

000

5100

000

5150

000

5150

000

Prince Edward Island

StudyArea

CapeTormentine

N o r t h u m b e r l a n d

S t r a i t

Borden-Carleton

Nova Scotia

New Brunswick

0 5 10 15 20 25

kilometres

°

1:750,000

Map scale 1:12,500 when printedon 24x36 size paperVertical Datum: LAT

NAD 1983 CSRS UTM Zone 20NProjection: Transverse MercatorDatum: North American 1983 CSRSFalse Easting: 500,000.0000False Northing: 0.0000Central Meridian: -63.0000Scale Factor: 0.9996Latitude Of Origin: 0.0000Units: Meter °0 100 200 300 400 500 600 700 800 900 1,000

metres

1:12,500


February 23, 2016

APPENDIX B

TSS Model ResultsNote: Results are inclusive of background concentrations


February 23, 2016

Figure B.1 Site NB-1: Water Depth, 3 m; Currents, Surface 4.6 and Bottom 4.9 cm/s.


February 23, 2016

Figure B.2 Site NB-3: Water Depth, 8m; Currents, Surface 9.6 and Bottom 7.7 cm/s.


February 23, 2016

Figure B.3 Site NB-3: Water Depth, 8m; Currents: Surface 113 and Bottom 85 cm/s

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