Attachment 9.1

TMEP Vessel Wake Assessment PRODUCED FOR TRANS MOUNTAIN PIPELINE ULC OCTOBER 29, 2018

Attachment 9.1 Attachment 9.1 TMEP Vessel Wake Assessment | Trans Mountain Pipeline ULC Revision 0 | October 29, 2018

Table of Contents Document Verification ...... i Disclaimer ...... iv Executive Summary ...... 1 1. Introduction, Purpose and Scope ...... 3 1.1. Introduction ...... 3 1.2. Purpose ...... 3 1.3. Scope of Work ...... 3 2. Regional Setting for Vessel Wakes ...... 5 2.1. Vessel Routes ...... 5 2.2. Regional Vessel Traffic ...... 5 2.3. Regional Waves and Wakes ...... 8 3. Vessel Wake Analytical Methods ...... 10 3.1. Kriebel and Seelig Method ...... 11 3.2. Maynord Method ...... 12 3.3. Fourier-Kochin Integration Method ...... 13 3.4. The Froude Number ...... 13 4. Wake Predictions ...... 16 4.1. Project Defined Scenarios ...... 16 4.1.1. Vessel Particulars ...... 17 4.2. Local Ferries ...... 18 4.3. Comparison with Ambient Wind-Wave Conditions...... 19 5. Project Wake Calculations ...... 25 5.1. Vancouver Harbour ...... 25 5.2. Strait of Georgia ...... 28 5.3. Haro Strait ...... 33 5.4. Strait of Juan de Fuca ...... 36 6. Discussion of Wake Effects ...... 38 6.1. Effects on Commercial Shipping ...... 40 6.2. Effects on Recreational Craft ...... 40 6.3. Anecdotal Experience ...... 42 7. Conclusions ...... 44 8. References ...... 45

List of Figures Figure 2-1: TMEP Vessel Routes ...... 6 Figure 2-2: Regional commercial vessel traffic routes [Ref e] ...... 7 Figure 2-3: TMEP Vessel Routes and Passenger/vehicle Ferry Routes ...... 7 Figure 2-4: Comparison of Projected TMEP traffic to existing (2018) regional traffic ...... 9 Figure 3-1: Vessel wake pattern (adaopted from Schierech, 2001)...... 10

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Figure 3-2: Example subcritical and supercritical wake ...... 14 Figure 4-1: Locations of recorded regional wind and wave Data (From Ref f) ...... 22 Figure 4-2: NOAA wave records, Juan de Fuca Strait (New Dungeness, OCT-MAR). (Ref f) ...... 23 Figure 4-3: Environment Canada wave records, Strait of Georgia (Halibut Bank, Apr-Sep) [Ref. f] ...... 24 Figure 5-1: Computed Vessel Wake for Aframax Tanker and Escort Tugs – Vancouver Harbour...... 26 Figure 5-2: Example Vessel Wake Patterns from Bulk Carrier and Power Boats ...... 27 Figure 5-3: Vancouver Harbour – Comparison of Vessel Wakes with Ambient Wave Climate ...... 28 Figure 5-4: Computed Vessel Wake for Aframax Tanker and Escort Tug ...... 29 Figure 5-5: Example wake pattern from BC Ferry inbound to Tsawwassen ...... 30 Figure 5-6: Comparison of Vessel Wake for Aframax Tanker and Escort Tug with BC Ferry ...... 31 Figure 5-7: Comparison of Vessel Wake for Aframax Tanker and Escort Tug with BC Ferry ...... 32 Figure 5-8: Strait of Georgia – Comparison of Vessel Wakes with Ambient Wave Climate ...... 33 Figure 5-9: Computed Vessel Wake for Aframax Tanker and Escort Tug ...... 34 Figure 5-10: Comparison of Vessel Wake from Aframax Tanker and Tug with WSDOT Ferry ...... 35 Figure 5-11: Haro Strait – Comparison of Vessel Wakes with Ambient Wave Climate ...... 36 Figure 5-12: Computed Vessel Wake for Aframax Tanker and Escort Tug ...... 37 Figure 5-13: Strait of Juan de Fuca – Comparison of Vessel Wakes with Ambient Wave Climate ...... 37 Figure 6-1: Aframax tanker with two escort tugs near Second Narrows, 2018-10-10 ...... 39 Figure 6-2: Aframax tanker with tug heading to Westridge Marine Terminal, 2018-10-10 ...... 39

List of Tables Table 3-1: Froude Number as a Function of Vessel Speed and Waterline Length ...... 14 Table 4-1: Project Defined Scenarios...... 16 Table 4-2: Aframax Vessel Data ...... 17 Table 4-3: Tug Data ...... 17 Table 4-4: Particulars of BC ferries operating in The Strait of Georgia Region...... 18 Table 4-5: Safe Boater Weather Warnings...... 19 Table 4-6: Summary of Ambient Wind-Wave Conditions...... 20

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Disclaimer

Moffatt & Nichol devoted effort consistent with (i) the level of diligence ordinarily exercised by competent professionals practicing in the area under the same or similar circumstances, and (ii) the time and budget available for its work, to ensure that the data contained in this report is accurate as of the date of its preparation. This study is based on estimates, assumptions and other information developed by Moffatt & Nichol from its independent research effort, general knowledge of the industry, and information provided by and consultations with the client and the client's representatives. No responsibility is assumed for inaccuracies in reporting by the Client, the Client's agents and representatives, or any third-party data source used in preparing or presenting this study. Moffatt & Nichol assumes no duty to update the information contained herein unless it is separately retained to do so pursuant to a written agreement signed by Moffatt & Nichol and the Client.

Moffatt & Nichol’s findings represent its professional judgment. Neither Moffatt & Nichol nor its respective affiliates, makes any warranty, expressed or implied, with respect to any information or methods disclosed in this document. Any recipient of this document other than the Client, by their acceptance or use of this document, releases Moffatt & Nichol and its affiliates from any liability for direct, indirect, consequential or special loss or damage whether arising in contract, warranty (express or implied), tort or otherwise, and irrespective of fault, negligence and strict liability.

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Attachment 9.1 Creative People, Practical Solutions.® Page iv TMEP Vessel Wake Assessment | Trans Mountain Pipeline ULC Revision A | October 29, 2018 Executive Summary

On 20 September 2018, through OIC P.C. 2018-1177, the Governor in Council (GIC) referred aspects of the National Energy Board (Board)’s Report for the Trans Mountain Expansion Project (Project) back to the Board for reconsideration (Reconsideration). The GIC’s direction followed a 30 August 2018 decision of the Federal Court of Appeal that quashed the GIC’s approval of the Project.

The Board is holding a public hearing to carry out the Reconsideration and has decided, on a principled basis, to include Project-related marine shipping between the Westridge Marine Terminal and the 12- nautical-mile territorial sea limit in the “designated Project” to be assessed under the CEAA 2012. The Board has issued a List of Issues for the Reconsideration hearing. The Board’s letter to Trans Mountain describing the additional Filing Requirements for Trans Mountain includes, with regard to potential safety, navigation, and disturbance of other vessels:

a) any additional evidence on the impacts of wakes created by Project-related marine shipping vessels at varying speeds on non-Project-related vessels crossing those wakes;

b) any additional evidence concerning measures to avoid, reduce, and/or offset the impacts of Project-related marine shipping vessels on non-Project-related vessels, including private recreational vessels.

This study addresses the two filing requirements listed above and supplements the vessel wake information presented previously as part of Volume 8A of the Application [Ref. a].

The previous assessment focused on identifying any potential negative effects where the vessel wakes reach the shorelines adjacent to the shipping route. This study expands upon the previous work and focusses on the potential for negative effects of wakes on other vessel traffic, including commercial traffic and private recreational vessels. This study determines the height and period of wakes generated by Project-related vessels (both tankers and tug boats), and compares their magnitude and frequency of occurrence to vessel wakes caused by other vessel traffic already operating in the region. A comparison is also made with typical natural ambient wave conditions caused by winds.

The wake calculations presented herein use an updated methodology compared to the results presented in Volume 8A, resulting in generally similar numerical values for the predicted wakes. For example, the previous assessment predicted that tankers moving at a speed of 12 knots would create a wake of 0.16m measured 100m away from the sailing line. In comparison, the current study predicts wake height in the same conditions would be even less, at less than 0.05m. Similarly, the previous assessment predicted a tug wake at 12 knots and 100m to be 0.23m in height, whereas the current study predicts the corresponding height would be about 0.30m. These differences are within the level of accuracy expected for the methodology used and do not change the conclusions, namely that Project-related vessel wakes are small.

Project-related vessel wakes were compared to predicted wakes generated by some of the common large vehicle and passenger ferries (both BC Ferries and Washington State Ferries) that frequently cross the TMEP vessel route. The results show that Project vessel wakes are much smaller and less frequent than those generated by the ferries which use those routes up to several times daily. This

Creative People, Practical Solutions.® Page 1 Attachment 9.1 TMEP Vessel Wake Assessment | Trans Mountain Pipeline ULC Revision A | October 29, 2018 indicates that Project vessel wakes are insignificant compared to other wakes already common along the route, and thus Project-related wakes are expected to have no impact on other commercial traffic.

Project-related wakes were also compared to natural wave conditions that could be expected under typical prevailing winds in the region. While wind speeds are often light or calm in the region (and hence the seas corresponding to those conditions are also small), winds frequently reach moderate to strong levels of 20 knots and more. In open waters such as the Strait of Georgia and Juan de Fuca Strait, seas can often exceed 0.5m in height and occasionally reach 1 - 2m in height. Such waves are well in excess of Project-related wakes. In more sheltered waters such as Vancouver Harbour, natural waves often reach 0.2 - 0.3m in height which is higher than Project related waves when transiting that portion of the route. Most recreational boaters who venture into open waters along the TMEP vessel route will be well accustomed to such wind and wave conditions, which occur frequently (e.g. every day for several days in a row). It is concluded that the Project-related wakes are small to negligible compared to conditions that most boaters will be accustomed to handling without difficulty, and therefore will have negligible impact on boaters. The same conclusion is reached for other smaller commercial traffic such as fishing vessels, water taxis, etc.

Overall, the current study corroborates and supports the previous work, while providing additional evidence that Project-related vessel wakes from tankers and support tugs are negligible compared to other vessel wakes, and to natural wind wave conditions that are already routinely encountered along the TMEP vessel route. Taken together with the previous results from Volume 8A, it is concluded that Project-related wakes will not have any discernable impact either on other waterway users, or on the adjacent shorelines. It is further concluded that no specific wake mitigation or management measures are warranted or recommended for Project-related vessel traffic.

Creative People, Practical Solutions.® Page 2 Attachment 9.1 TMEP Vessel Wake Assessment | Trans Mountain Pipeline ULC Revision A | October 29, 2018 1. Introduction, Purpose and Scope

1.1. Introduction

a) any additional evidence on the impacts of wakes created by Project-related marine shipping vessels at varying speeds on non-Project-related vessels crossing those wakes;

1.2. Purpose

This study supplements the vessel wake information presented previously as part of Volume 8A of the Application [Ref. a]. The previous work is expanded by comparing predicted Project-specific vessel traffic wakes more specifically to other commercial vessel traffic (primarily passenger and vehicle ferries) that are commonly encountered along the TMEP vessel route. The TMEP vessel wakes are also compared to ambient wind wave conditions in the region for context. This report uses an updated methodology that provides improved visualization of vessel wake patterns and how they disperse over distance from the vessel sailing line. The results of this study differ slightly from the earlier results in quantitative terms due to a different methodology used, but the conclusions are essentially the same and support the previous work.

1.3. Scope of Work

The scope of work for this study is as follows:

1. Build on the previous TMEP wake study included in the Application Volume 8A and the TMEP TERMPOL studies to provide graphics showing the vessel navigation route and study locations.

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2. Evaluate typical wake patterns for other commercial vessel traffic (in particular BC Ferries and Washington State Ferries) in the region crossing or adjacent to the TMEP vessel route.

3. Compare the predicted vessel wake heights to natural ambient wave conditions caused by the wind, using the TMEP metocean analysis previously completed by EBA along the route. The EBA study provides recorded wave data at two stations along the TMEP vessel route: Halibut Bank (representative of the Strait of Georgia) and New Dungeness (representative of Juan de Fuca).

4. Predict wake heights and patterns for Aframax vessels in the laden condition (i.e. worst case) and at three speeds (7, 10 and 12 knots), representing typical vessel speeds in Vancouver Harbour, Haro Strait, and Straits of Georgia /Juan de Fuca respectively, using the appropriate tug escort pattern for that location.

5. Provide a summary report describing the methodology, summary of results and conclusions. The specific questions or issues to be answered in the report include:

• What are the anticipated wake heights of Project vessels under the defined conditions? Provide wake height and period as a function of distance from the sailing line at the specified velocities and tug escort configurations.

• How do the predicted wakes compare to other existing vessel traffic (e.g. ferries) and to natural ambient waves under typical wind conditions at up to 3 locations (Strait of Georgia, Juan de Fuca Strait, and Vancouver Harbour)?

• Comment on the significance of Project-related vessel wakes relative to existing conditions on other vessels, including commercial and recreational traffic.

Creative People, Practical Solutions.® Page 4 Attachment 9.1 TMEP Vessel Wake Assessment | Trans Mountain Pipeline ULC Revision A | October 29, 2018 2. Regional Setting for Vessel Wakes

2.1. Vessel Routes

Deep sea vessel traffic travelling between the Westridge Marine Terminal and the open sea west of Vancouver Island follow well-established traffic routes (see Figure 2-1). The vessel routes and navigation procedures including vessel speed profile and escort tugs are described in detail in the Volume 8C TERMPOL Studies [Refs. b,c,d,e]. The vessel routes shown in Figure 2-1 apply not only to TMEP tanker traffic but other large commercial vessels (e.g. dry bulk carriers, cruise ships, container vessels etc.) traveling to and from Burrard Inlet. However for ease of reference the vessel routes shown in Figure 2-1 will be referred to simply as the “TMEP routes”. Also, it is noted that the black and blue lines depicting the vessel routes are idealized vessel tracks within a designated traffic lane as defined by the established Traffic Separation Scheme (TSS). The width of the traffic lanes themselves can range up to 1.5 nautical miles or more. At the discretion of the pilot, actual vessel tracks may depart somewhat from the idealized tracks to account for other vessel traffic, wind, tide and current conditions, etc. while generally staying within the traffic lane.

2.2. Regional Vessel Traffic

The TMEP vessel routes shown in Figure 2-1 cross numerous other vessel routes in the region that are used by ferries, tug boats, fishing vessels, etc. as shown in Figure 2-2. Figure 2-2 is adapted from the TMEP vessel traffic risk assessment conducted by DNV, submitted as part of Volume 8C of the Application [Ref. e]. The routes are colour-coded to represent their relative traffic volumes, ranging from less than one vessel per day to more than 10 per day. Routes used by ferry traffic (including BC Ferries and Washington State Ferries) are shown in Figure 2-3.

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FIGURE 2-1: TMEP VESSEL ROUTES

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FIGURE 2-2: REGIONAL COMMERCIAL VESSEL TRAFFIC ROUTES [REF E]

FIGURE 2-3: TMEP VESSEL ROUTES AND PASSENGER/VEHICLE FERRY ROUTES

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2.3. Regional Waves and Wakes

All moving vessels produce a wake, the height of which is dependent on a number of factors including the vessel size and shape, vessel speed, water depth and other factors. In general vessel wakes are highest close to the vessel, and diminish in height as they spread out from the sailing line. The reduction in wake height over time is mainly due to the radiating energy being spread out over a greater area, but energy dissipation also occurs through viscous losses, especially if the waves are breaking. Breaking waves in deep water (i.e. whitecaps) are common for wind waves and for some types of vessel-generated wakes, but wave breaking is rare for deep sea vessel wakes due to their characteristically low steepness (i.e. ratio of height to length).

The significance (or not) of a particular vessel wake size in a particular location is best assessed within the context of how it compares to existing ambient wave conditions. This study therefore focuses on comparing the size and frequency of Project-related vessel wakes against wakes generated by other traffic already operating in the region, as well as the natural waves and swells generated by the wind.

In addition to the height and period of a wake wave, the frequency1 of occurrence should also be considered. For example, a wake that occurs several times per day or hour might be considered more objectionable compared to the same wave occurring once per day or less.

One measure of wake frequency or exposure at any given location is to compare the Project vessel traffic volumes to other types of traffic operating in the same area. Figure 2-4 shows the volume of anticipated TMEP Project traffic compared to other types of existing vessel traffic, where traffic volume is measured in “sailed nautical miles”, i.e. the sum total length of the voyages sailed by various types of vessels within the region. Traffic volumes cited here are “reporting traffic”, i.e. larger vessels that participate in the compulsory Vessel Traffic Services (VTS) system. Non-reporting vessel traffic (e.g. most recreational vessel traffic) is not included.

The “existing traffic” volumes are based on the estimated 2018 traffic volumes, extracted from the vessel traffic study [Ref. c] submitted as part of the Application. In this example, it is clear that the vessel wakes generated by TMEP Project vessels is a small fraction (approximately 2.3%) of the total vessel wakes generated in the region. The TMEP traffic wakes would be even less significant if recreational vessel wakes are included.

In Section 4 below it will be shown that Project vessel wakes are also smaller than many of the large commercial vessels already operating the region. Since the Project-related wakes are both smaller and much less frequent than wakes from other existing commercial vessels, it is clear that Project- related vessel wakes are relatively insignificant compared other vessels.

1 The term “frequency” in this report is used to describe how often the event occurs, as distinct from the wave parameter frequency f which is the inverse of the wave period (f=1/T), where T is the wave period (i.e. the time in seconds between successive wave crests).

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FIGURE 2-4: COMPARISON OF PROJECTED TMEP TRAFFIC TO EXISTING (2018) REGIONAL TRAFFIC

Creative People, Practical Solutions.® Page 9 Attachment 9.1 TMEP Vessel Wake Assessment | Trans Mountain Pipeline ULC Revision A | October 29, 2018 3. Vessel Wake Analytical Methods

A vessel in transit will produce a particular wake pattern, which is outlined in Figure 3-1, adapted from Schierech (2001). As the vessel displaces water during its passage, a varying pressure distribution develops along the hull of the vessel producing an increased pressure at the bow and stern and a pressure drop along the midsection. The associated pressure gradients produce waves that propagate out from the bow and the stern of the vessel.

FIGURE 3-1: VESSEL WAKE PATTERN (ADAOPTED FROM SCHIERECH, 2001).

The waves originating from the bow (Figure 3-1) are commonly called “bow wake” and follow a diverging pattern along the path of the vessel as they propagate out from the sailing line. A series of transverse waves, or “stern waves”, propagate along the sailing line in the direction opposite to the vessel transit.

The stern waves are typically smaller than the bow wake. The largest wave heights are encountered where the transverse waves and the diverging waves intersect, which occurs along the cusp locus line, which has been found to form an angle of 19°28’ relative to the sailing line.

A detailed derivation of vessel wake is highly complex as it depends on the particular hull shape of the vessel and essentially its frictional resistance during transit. It is only with modern computational methods that solutions of the underlying equations of physics are starting to develop, although the mathematics involved is extensive and computationally very intensive. The bulk of the present research has focused on developing simplified semi-empirical relationships to describe the overall characteristics of vessel wakes. The main parameters governing vessel wake formation have been identified to be:

• The speed of the vessel, with increasing speed yielding an increase in wave heights.

• The water depth, with decreasing water depth producing an increase in wave heights.

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• The Froude Number, which relates the above parameters to the celerity (travel speed) of a shallow-water wave, and in the case of deep water, to the overall dimension of the vessel.

As waves propagate out from the sailing line, the wave height attenuates with distance traveled and the wake become less prominent.

Other parameters that affect wake formation (but are less well understood in past research) include the hull shape of the vessel, its draft, underkeel clearance, and confinement of the water body surrounding the vessel.

In the following sections, a range of methods adopted in the present study are described. For consistency, the symbols used in each method are unified to represent the same input parameter.

3.1. Kriebel and Seelig Method

Kriebel and Seelig (2005) proposed an empirical model, approximating the variation of secondary wave heights with distance as:

𝐻𝐻 𝑦𝑦 = ( 0.1) 1 2 − 𝛽𝛽𝑉𝑉𝑠𝑠 ∗ 2 𝑦𝑦 3 𝐻𝐻 𝐹𝐹 − � � Where is the vessel speed, the acceleration𝑔𝑔 due to gravity,𝐿𝐿 is the distance from the sailing line, is the length of the vessel, is a modified Froude number, and an empirical coefficient based on 𝑉𝑉𝑠𝑠 𝑔𝑔 𝑦𝑦 the hull shape of the vessel. ∗ 𝐿𝐿 𝐹𝐹 𝛽𝛽 Kriebel and Seelig state that the Froude number is defined by the water depth-to-draft ratio . They further state that vessels transiting deep water ( > 5) produce a wake size that depends on 𝐹𝐹 ℎ⁄ 𝐷𝐷 the length-based Froude number , and vessels transiting shallow water ℎ⁄ 𝐷𝐷 ( < 1.5) produce a wake size that depends on the depth-based Froude number . Between these 𝐹𝐹𝐿𝐿 two water depths, Kriebel and Seelig determined that a modified Froude number was more ℎ⁄ 𝐷𝐷 𝐹𝐹𝑑𝑑 appropriate. ∗ 𝐹𝐹 = ( ) ∗ = 2.35(1 ) 𝐹𝐹 𝐹𝐹𝐿𝐿𝑒𝑒𝑒𝑒𝑒𝑒 𝛼𝛼⁄ 𝐷𝐷ℎ Where is the vessel draft, the water depth,𝛼𝛼 and an− 𝐶𝐶empirical𝑏𝑏 coefficient dependent on the vessel block coefficient Cb, defined as: 𝐷𝐷 ℎ 𝛼𝛼 = ∇ 𝐶𝐶𝑏𝑏 Where is the volume displacement and , , and 𝐿𝐿𝐿𝐿 i𝐿𝐿s the length, beam, and draft of the vessel.

The coefficient∇ is defined as: 𝐿𝐿 𝐵𝐵 𝐷𝐷

𝛽𝛽 = 1 + 8 0.45 2 3 𝐿𝐿 𝛽𝛽 ∙ 𝑡𝑡𝑡𝑡𝑡𝑡ℎ � � � − � Where is the entrance length. 𝐿𝐿𝑒𝑒

𝐿𝐿𝑒𝑒

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Additional characteristic proportions of the wake can be determined as follows per CEM (2006). The speed of wake propagation (celerity) is given by:

= ( )

𝑠𝑠 Where is the celerity, is the vessel speed,𝐶𝐶 and𝑉𝑉 𝑐𝑐𝑐𝑐𝑐𝑐 is 𝜃𝜃the angle of wave propagation with respect to the sailing line as defined in Figure 3-1. The angle of wave propagation has been found to be related 𝐶𝐶 𝑉𝑉𝑠𝑠 𝜃𝜃 to the Froude Number as follows:

= 35.27° 1 ( ) 12 𝐹𝐹𝑠𝑠−1 Where is the Froude Number and 𝜃𝜃is the exponential� − 𝑒𝑒 function.�

𝑠𝑠 The wave𝐹𝐹 length is determined from the𝑒𝑒 dispersion relation given by:

2 = tanh 2 2 𝑔𝑔𝑔𝑔 𝜋𝜋ℎ 𝐶𝐶 � � Where is the celerity, is the water depth, is 𝜋𝜋the wave𝐿𝐿 length, and the acceleration due to gravity. The wave period, , can be resolved from: 𝐶𝐶 ℎ 𝐿𝐿 𝑔𝑔 𝑇𝑇 = 𝐿𝐿 𝑇𝑇 In deep water where the propagation of waves is unaffected𝐶𝐶 by the bottom topography, as is the case for vessel wake propagation along most of the TMEP route, the wave length and wave period terms reduce to:

2 = 𝜋𝜋 2 And 𝐿𝐿 𝐶𝐶 𝑔𝑔 2 = 𝜋𝜋 𝑇𝑇 𝐶𝐶 𝑔𝑔 3.2. Maynord Method

The Maynord (2005) method is applicable to semi-planing and planning small craft. The variation of the wake with distance from the boat is given by: . = . −0 42 −0 58 𝑠𝑠 1⁄ 3 𝐻𝐻 𝐶𝐶∇ ∙𝐹𝐹 � 1⁄ 3� ∇ Where is the volumetric displacement of the hull,∇ is a coefficient that characterizes the hull type, and is the displacement Froude number given by: ∇ 𝐶𝐶 𝐹𝐹∇ = 𝑠𝑠 ∇ 𝑉𝑉 𝐹𝐹 1⁄ 3 Where is the vessel speed and is the gravitational�𝑔𝑔 ∙∇ acceleration.

𝑉𝑉𝑠𝑠 𝑔𝑔

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3.3. Fourier-Kochin Integration Method

Wake patterns produced by vessels in transit can be approximated by the free-surface elevation Z given as: 1 ( + ) ( , ) = ( ) 𝜋𝜋⁄ 2 ∞ 2 −𝑖𝑖𝑖𝑖 𝑥𝑥𝑥𝑥𝑥𝑥𝑥𝑥𝑥𝑥+𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦 𝑘𝑘 𝑃𝑃 𝑖𝑖𝑖𝑖 2 2 𝑍𝑍 𝑥𝑥 𝑦𝑦 ℜ � � 𝑒𝑒 0 𝑑𝑑𝑑𝑑 𝑑𝑑𝑑𝑑 where 𝜋𝜋 −𝜋𝜋⁄ 2 0 𝑘𝑘 −𝑘𝑘 𝑠𝑠𝑠𝑠𝑠𝑠 𝜃𝜃 1 + = ( , ) 𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖+𝑘𝑘𝑘𝑘 𝑃𝑃 𝑖𝑖𝑖𝑖 − � 𝑌𝑌𝜉𝜉 𝜉𝜉 𝜁𝜁 𝑒𝑒 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 Which is termed a Fourier-Kochin representation.𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖 𝑅𝑅 The method is described in Tuck et al. (2001) and Tuck (2003) and has been demonstrated to produce results comparable to commercial Computational Fluid Dynamic (CFD) codes, Revathi et al. (2012).

Mathematically the method relies on thin-ship theory; that the vessel moves at a steady constant speed; and the water depth is infinite. It is suitable for application to the TMEP vessels in that vessel hulls are relatively elongate, vessels move at a fairly constant service speed when in transit; and the water is deep for most of the TMEP vessel route (i.e. ( > 5), as described in Section 3.1).

The particular application of the method primarily resolvesℎ⁄ 𝐷𝐷 the far field wake pattern propagating aft and away from the vessel, but does not resolve the water surface elevation right at the hull. Additionally, because the method assumes a simplified hull-shape, wave height estimates computed are only indicative, and ideally need to be calibrated with field data, or comparative CFD analysis that has been verified with field measurements. However, even without quantitative calibration against real- world measurements, the method provides a useful qualitative means of comparing wakes from different sizes and speeds of vessels in relative terms.

3.4. The Froude Number

Common to all of the above methods is a relation to the Froude Number, , defined by:

𝐹𝐹 = 𝑉𝑉 𝐹𝐹 which provides a speed-length relationship. In shallow�𝑔𝑔 ∙𝐿𝐿 water, the square-root term equates to the propagation speed of a shallow-water wave, which is dependent on the water depth. Beyond a certain water depth, the Froude number is independent of depth, and the length scale transitions to the length of the vessel which acts as a physical limit on the wave length generated.

The Froude number is closely tied to the resistance associated with a vessel moving through the water. In general terms, vessels that have the same Froude number produce a similar wake, even if their size or geometry are otherwise different.

With increasing speed, the resistance increases and the result is the formation of the wake, which increases with speed. Conditions at Froude numbers less than 1 are termed subcritical (See

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Figure 3-2). Under these conditions the vessel wake takes the form of the characteristic V-pattern that is commonly observed.

FIGURE 3-2: EXAMPLE SUBCRITICAL AND SUPERCRITICAL WAKE

If sufficient power is applied it is possible to achieve a Froude number greater than 1 (supercritical). As the Froude number increases, the V-shape pattern of the wake transitions to become more parallel to the vessel track. This wake pattern is commonly observed for very fast-moving vessels such as speed boats and catamarans.

Table 3-1 indicates Froude numbers as function of vessel speeds and their waterline length. Large, ocean-going and relatively slow moving vessels such as tankers fall in the category indicated in green. Tugs (pink) typically achieve similar tops speeds as the ocean-going vessels, but are shorter in length, and the Froude number is consequently higher. Ferries (yellow) have intermediate length and can achieve relatively high transit speeds. Power boats (red) have short lengths overall and can achieve exceptionally high speeds. These have the ratio that produces the highest Froude numbers.

TABLE 3-1: FROUDE NUMBER AS A FUNCTION OF VESSEL SPEED AND WATERLINE LENGTH

Speed (knots) 5 10 15 20 30 40 50

5 0.4 0.7 1.1 1.5 2.2 2.9 3.7

10 0.3 0.5 0.8 1.0 1.6 2.1 2.6

20 0.2 0.4 0.6 0.7 1.1 1.5 1.8

50 0.1 0.2 0.3 0.5 0.7 0.9 1.2

100 0.1 0.2 0.2 0.3 0.5 0.7 0.8

Waterline Length (m) 200 0.1 0.1 0.2 0.2 0.3 0.5 0.6

300 0.0 0.1 0.1 0.2 0.3 0.4 0.5

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In terms of the vessels considered in this study, their respective Froude number ranges lead to the following interpretation:

• Tankers. Wake is very small.

• Tugs. Typical wake is moderate but increases with their speed.

• Ferries. Typical wake is small in port and harbour areas where approach and departure velocities are low. Wake can become large when ferries are at their cruising speed.

• Power boats. Typical wave can be large for these high-powered vessels, particularly those of high mass.

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4.1. Project Defined Scenarios

The Project-defined scenarios are representative of an outbound transit of a laden tanker from the terminal to the open sea. The characteristic segments along the trip include passage through Vancouver Harbour, the Strait of Georgia, Haro Strait, and the Strait of Juan de Fuca. These scenarios are summarized in Table 4-1 accompanied by illustrations of the respective escort tug configurations.

TABLE 4-1: PROJECT DEFINED SCENARIOS. Segment 1 2 3 4 Vancouver Strait of Strait of Waterbody Haro Strait Harbour Georgia Juan de Fuca Central Harbour Outer Harbour Boundary Pass Race Rocks Range Inner Harbour Boundary Pass Race Rocks J Buoy Transit Speed 7 knots 12 knots 10 knots 12 knots Typical Water Depth 30 m 130 m 200 m 165 m

Tug Support 2 tugs: B(t) / S(t) 1 tug: B(u) 1 tug: S(t) 1 tug: B(u) Tug Bollard Pull 30 MT / 70 MT 70 MT 70 MT 110 MT

m m 500 500

Tug Escort Configuration m m 90 90 - - 60 60

Tug configurations: Bow (B), Stern (S), tethered (t), untethered (u)

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4.1.1. Vessel Particulars

Particulars of the Aframax tanker and tugs evaluated in this study are summarized in Table 4-2 and Table 4-3. The Aframax tanker is representative of the largest vessel that will visit the terminal. A typical Aframax tanker representative of both the current tankers calling at the Westridge Marine Terminal and future TMEP traffic is shown in Figure 6-1 and Figure 6-2 in Section 6.

The tugs are categorized by their bollard pull, which is a measure of their pulling power and implicitly their size. Tugs are also commonly characterized by the type of environment they work in, such as river tugs, coastal tugs, and ocean tugs. River tugs frequent the Fraser River and other inland waters around Vancouver. Coastal tugs provide a wide range of services around Vancouver and work in harbour and coastal areas. Ocean tugs have the capability to navigate offshore in the open ocean and are typically larger in size. Tugs in service to support the transit, berthing and unberthing of large ocean-going vessels are commonly referred to as ship assist tugs, escort tugs, or tractor tugs.

TABLE 4-2: AFRAMAX VESSEL DATA Vessel Type Crude Oil Carrier Class Aframax DWT (MT) 120,000 LOA (m) 250.0 Beam (m) 44.0 Max Draft (m) 15.0 Typical Working Draft in Port of Vancouver (m) 12.82

TABLE 4-3: TUG DATA

Vessel Bollard Pull Particulars 30 MT 70 MT 110 MT Type Coastal Tug Coastal Tug Ocean Tug LOA (m) 25.2 28.2 40.7 Beam (m) 7.6 12.6 14.4 Draft (m) 4.3 5.4 5.5 GRT (t) 149 441 927

2 The maximum draft permitted at Second Narrows under VFPA’s operating rules (TCZ-2) is 13.5m, however TMEP Project vessels are anticipated to sail at a lesser draft due to restrictions in the available daily draft at the Second Narrows for this size of vessel.

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4.2. Local Ferries

Particulars of ferries considered in the study are summarized in Table 4-43. These ferries are included in the wake analysis because they make frequent transits through coastal waters to port facilities, predominantly in the same waters as tankers visiting the TMEP Terminal.

It is worth noting that the typical objective of a tanker (and other commercial cargo vessels) is to carry a large amount of cargo over long distances as efficiently as possible. Cargo vessels transit at a cruising speed that minimizes their frictional resistance through the water. While a portion of the resistance is due to viscous drag, a larger component is due to wave-making resistance, which is exhibited by formation of the vessel wake. A vessel wake radiating outward from a ship represents energy that the vessel has put into the water. Since the energy in a wave is proportional to the square of its height, reducing the wake height means a reduction in radiated energy. Lower energy loss translates into less fuel consumption, and since the cost of fuel is one of the largest operating expenses for commercial ships, naval architects and ship hull designers of commercial vessels generally try to optimize the hull design to minimize their generated wakes. Ocean-going cargo vessels typically feature streamlined hulls and bulbous bows, which serve to reduce friction and their wake.

Ferries on the other hand operate on a schedule to meet a specific time table where speed is often of the essence. In some cases ferries have the flexibility to apply a greater amount of engine power to increase speed to make up for any delays. Ferries often produce more substantial wake due to the engine power applied and higher Froude number, as well as much more frequent transit (e.g. some BC ferries routes that cross the TMEP route see up to 15 round trips per day at peak times).

TABLE 4-4: PARTICULARS OF BC FERRIES OPERATING IN THE STRAIT OF GEORGIA REGION.

Tsawwassen Tsawwassen Tsawwassen Tsawwassen Sidney – Route – Swartz Bay – Swartz Bay – Swartz Bay – Duke Point Anacortes Spirit of Spirit of Vessel Coastal Queen of British Vancouver Chelan Particulars Celebration Alberni Columbia Island Operator BC Ferry BC Ferry BC Ferry BC Ferry WSDOT Length overall 167 m 167 m 160 m 139 m 100 m Beam 26.6 m 32.9 m 27.8 m 27.1 m 24.0 m Draft 4.6 m 5.0 m 5.8 m 5.8 m 5.1 m Capacity 2,100 2,100 1,604 1,200 1,200 passengers passengers passengers passengers passengers and crew and crew and crew and crew and crew 358 vehicles 358 vehicles 310 vehicles 280 vehicles 124 vehicles Gross 21,939 18,747 21,777 5,863 2,477 tonnage

3 Data in Table 4-4 were obtained from multiple sources including BC Ferries website, Clarkson’s Register, and Wikipedia, and have not been independently verified.

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Tsawwassen Tsawwassen Tsawwassen Tsawwassen Sidney – Route – Swartz Bay – Swartz Bay – Swartz Bay – Duke Point Anacortes Spirit of Spirit of Vessel Coastal Queen of British Vancouver Chelan Particulars Celebration Alberni Columbia Island Displacement 11,642 tonnes 11,681 tonnes 10,034 tonnes 6,422 tonnes 3,460 tonnes Deadweight 2,925 tonnes 2,925 tonnes 2,301 tonnes 1,981 tonnes 1,941 tonnes tonnage Propulsion 21,394 hp 21,394 hp 21,444 hp 12,000 hp 5,000 hp Service speed 19.1 knots 19.1 knots 19.7 knots 19.6 knots 15.6 knots Maximum 19.5 knots 19.5 knots 23.0 knots 21.0 knots 16.0 knots Speed

4.3. Comparison with Ambient Wind-Wave Conditions

Environment Canada issues marine wind warnings when winds reach certain speeds. A “Strong Wind Warning” is issued (in summer months only) 4 when the wind speed exceeds or is expected to exceed 20 knots (37 kph). A summary of wind conditions and warnings commonly used for pleasure boaters is shown in Table 4-5. Wind speeds at Gale Force and above also correspond to the Beaufort Wind Scale.

TABLE 4-5: SAFE BOATER WEATHER WARNINGS. Wind Category Wind Speed (knots) Warning Light Wind 1 – 14 None Moderate Wind 15 – 19 None Strong Wind 20 – 33 Strong Wind Warning Gale 34 – 47 Gale Warning Storm 48 – 63 Storm Warning Hurricane 64+ Hurricane Warning

While wind conditions in local waters are often calm or light (and the corresponding wind-generated waves are small or nonexistent), winds up to the Strong Wind Warning threshold (20 knots) can be expected to occur frequently, often every day for multiple days. As a result many recreational boaters consider winds of up to about 20 knots to be somewhat routine conditions that could be expected on a typical summer day. The waves associated with that wind strength would also be considered routine. M&N has therefore used the 20 knot threshold to compare vessel wakes to the ambient wind-wave

4 Environment Canada’s Strong Wind Warnings are geared toward smaller vessels such as recreational boats, and are only issued in summer months which account for the majority of recreational boat traffic.

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Wind-wave growth depends greatly on wind speed and fetch length. In this study, formulae in the Coastal Engineering Manual were used for wind-wave growth (USACE, 2002). Table 4-6 provides the estimated significant wave height and peak wave period during sustained 20 knot winds, up to the longest fetch length possible at each segment of the transit. The most-likely wave conditions (representative of typical fetches that may be most commonly encountered by boaters in those areas) are highlighted in yellow.

TABLE 4-6: SUMMARY OF AMBIENT WIND-WAVE CONDITIONS AT 20 KNOTS OF WIND.

Significant Wave Height (m) / Peak Wave Period (s) Fetch (mi) Vancouver Strait of Juan de Fuca HaroStrait Harbour Georgia Strait 1 0.21 / 1.4 0.21 / 1.4 0.21 / 1.4 0.21 / 1.4 3 0.36 / 2.0 0.36 / 2.0 0.36 / 2.0 0.36 / 2.0 5 - 0.47 / 2.4 0.47 / 2.4 0.47 / 2.4 10 - 0.66 / 3.0 0.66 / 3.0 0.66 / 3.0 40 - 1.32 / 4.8 1.32 / 4.8 1.32 / 4.8 70 - 1.74 / 5.8 - 1.74 / 5.8 100 - - - 2.08 / 6.5

Reference is provided below to recorded wave data obtained in the region. An extensive summary of regional wind, wave and other meteorological data was provided as part of the Application (Ref. f). While there are numerous stations with recorded wind data, there are only three recorded wave buoy stations along the TMEP vessel route: Neah Bay (NOAA buoy, west end of Juan de Fuca Strait); New Dungeness (NOAA buoy, east end of Juan de Fuca Strait); and Halibut Bank (Environment Canada buoy, Strait of Georgia.) See Figure 4-1 for the station locations.

Representative measured wave climate summaries are shown below for New Dungeness in winter months (October-March) in Figure 4-2. Wave records from Halibut Bank in summer months (April- September) are shown in Figure 4-3. The wave diagrams show the wave height and relative frequency (percent occurrence) for each of 16 compass directions, as well as the percentage measurements that were recorded as “calm” (i.e. wave height less than 0.1m).

In general, the strongest winds tend to occur in winter, so the winter wave records tend to indicate somewhat larger waves than summer. Most recreational boating traffic takes place in summer months, so summer conditions are more likely to reflect the experience of pleasure boaters.

Referring to Figure 4-2, winter wave conditions in the Juan de Fuca Strait are:

• almost always from the west or west-southwest;

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• calm or less than 0.1m about 14.5% of the time;

• between 0.2m and 0.4m (light waves) 35% of the time;

• between 0.4 and 1.0m (moderate waves) 21% of the time

• greater than 1m (large waves) about 5.7% of the time.

Similarly, referring to Figure 4-3, summer waves in the Strait of Georgia are:

• generally from the northwest (often associated with high pressure systems or fair weather), or from the southeast (often associated with low pressure systems or rainy weather);

• calm or less than 0.1m about half (46.6%) of the time;

• between 0.2m and 0.4m (light waves) 27% of the time;

• between 0.4 and 1.0m (moderate waves) about 25% of the time

• greater than 1m (large waves) about 1% of the time.

Refer to the EBA TMEP metocean study [Ref. f] for more information on regional waves conditions.

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FIGURE 4-1: LOCATIONS OF RECORDED REGIONAL WIND AND WAVE DATA (FROM REF F)

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FIGURE 4-2: NOAA WAVE RECORDS, JUAN DE FUCA STRAIT (NEW DUNGENESS, OCT-MAR). (REF F)

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FIGURE 4-3: ENVIRONMENT CANADA WAVE RECORDS, STRAIT OF GEORGIA (HALIBUT BANK, APR-SEP) [REF. F]

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5.1. Vancouver Harbour

During transits through Vancouver Harbour, outbound laden Aframax tankers will be assisted by two escort tugs. Figure 5-1 provides a plan view of the vessel wake computed using the Fourier-Kochin integration method. The scenarios used for the analysis are summarized in Table 4-1 (Segment 1). Vessel particulars for the Aframax Tanker and Escort Tugs are summarized in Table 4-2 and Table 4-3.

The extent of the area shown in Figure 5-1 measures 3 km × 3 km, which is approximately the size of the Vancouver Inner Harbour basin.

The wake from the Aframax Tanker and Escort Tugs is barely discernible in the figure and extends a short distance out from the vessel sailing line. The scale on the right hand side of the figure indicates that the height of individual wake waves is within about 0.12 metres from wave trough to wave crest.

The wake pattern shown in Figure 5-1 is similar to the photographs in Figure 6-1 and Figure 6-2, which show an actual Aframax tanker in ballast with two escort tugs, inbound toward the Westridge Marine Terminal. In Figure 6-1 the forward tug is stationed on the vessel’s port side rather than the starboard side used in the numerical model, so the overall wake pattern is opposite-handed.

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Metres

0 100 200 300 400 500

FIGURE 5-1: COMPUTED VESSEL WAKE FOR AFRAMAX TANKER AND ESCORT TUGS – VANCOUVER HARBOUR

There is a large population of recreational boats (more than 5,000) in and around Vancouver and a range of small to medium and large power boats (including fishing vessels and light commercial boats such as water taxis), many of which regularly use the waters of Vancouver Harbour and the adjacent English Bay. As well, Translink’s Seabus service makes regular north-south crossings between Lonsdale Quay and Waterfront Station in central Vancouver Harbour several times per hour. Figure 5-2 provides a snapshot from satellite imagery of a bulk carrier passing under the Lions Gate Bridge. The image also captures vessel wake from a number of power boats. In this context, the bulk carrier seen in the photo can be considered comparable to an Aframax Tanker in terms of its size and generic hull shape. The photo clearly shows that the wake associated with the large bulk carrier is barely noticeable, whereas the wakes from the recreational boats (white streaks from power boats) are very apparent.

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FIGURE 5-2: EXAMPLE VESSEL WAKE PATTERNS FROM BULK CARRIER AND POWER BOATS

Figure 5-3 provides a comparison of wakes from a range of vessels based on the Kriebel (2005) analysis methodology. The results show that the wake from the Aframax Tanker (black line) and Escort Tugs (yellow lines) will be very limited during the transit through Vancouver Harbor. This is primarily due to their slow speed, which is limited to about 7 knots. This speed is a practical low speed that still provides proper steerage for safe navigation.

The figure also shows the typical wake wave height variation associated with power boats cruising at their maximum cruising speed. The common range of power boats in the area is captured within the range from the 30’ power boat (red line) and the 65’ power boat (dark red line).

The results show that wakes from power boats can be on the order of 0.6 to 1.2 metres right alongside these vessels but diminish with distance from the sailing line. It is evident that the wakes from these recreational vessels far exceed the wakes produces by the Aframax Tanker and Escort Tugs. An individual boater, even as far out as 300 metres from the sailing line (and further), would experience the wake from the recreational power boaters as waves up to 0.2 metres in height, but would not be able to register wake from the Aframax Tanker and Escort Tugs, which is essentially nil.

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Figure 5-3 also provides a comparison of vessel wakes with the ambient wave climate within Vancouver Harbour, which is indicated by the light blue dashed line. In this context, the ambient wave climate is defined as prevailing conditions up to the point where a Strong Wind Warning would be issued, which as noted earlier occurs when winds reach 20 knots. At higher wind speeds (and associated wave conditions), most recreational boaters would seek shelter and return to port, although some boaters (notably sailors, wind surfers and kite boarders) specifically seek out stronger wind conditions because of the added thrill and larger waves.

The figure shows that the larger (65’) power boats frequently exceed the ambient wave conditions in the Inner Harbour. In addition to the wake wave height, the wave period plays an important role in terms of the exposure of a vessel to wave action. The analysis found that the wave period of wake waves from the Aframax Tanker and Escort Tugs will be on the order of 2 seconds, which is comparable to seas that would develop under light winds. The wave period from power boats traveling at their maximum speed can exceed 6-10 seconds or more, which is comparable to ocean swell.

Vancouver Harbour 1.2 Aframax Tanker 1.0 Tug 30 TBP Tug 70 TBP 0.8 65' Power Boat 30' Power Boat 0.6 Strong Wind Warning

0.4 Wave Height (m)

0.2

0.0 0 50 100 150 200 250 300 Distance from Sailing Line (m)

FIGURE 5-3: VANCOUVER HARBOUR – COMPARISON OF VESSEL WAKES WITH AMBIENT WAVE CLIMATE

5.2. Strait of Georgia

As an outbound Aframax Tanker departs Vancouver Harbour and heads out of English Bay into the Strait of Georgia, the tug assist pattern changes to an un-tethered escort tug located approximately 500 metres ahead of the Aframax Tanker. In these open waters, the safest means of navigation for the Aframax Tanker is to operate under its own power, using the escort tug in the role of a look-ahead support vessel.

Figure 5-4 provides a plan view of the vessel wake computed using the Fourier-Kochin integration method over a 3 km × 3 km area. The basis of the analysis is summarized in Table 4-1 (Segment 2). Refer to Table 4-2 and Table 4-3 for vessel particulars for the Aframax Tanker and Escort Tug.

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The wake from the Escort Tug is noticeable in the figure, whereas the wake from the Aframax Tanker is barely discernible. The scale indicates that the height of individual wake waves is within about 0.75 metres from wave trough to wave crest. Wake waves of this magnitude will occur right around the hull of the tug and diminish rapidly with distance away from the sailing line.

Metres

0 100 200 300 400 500

FIGURE 5-4: COMPUTED VESSEL WAKE FOR AFRAMAX TANKER AND ESCORT TUG

Other vessels that make frequent transits in this area include the BC Ferries. Several of the ferry routes make their way across the Strait of Georgia between Tsawwassen, Swartz Bay and Duke Point (see Figure 2-3). Table 4-4 summarizes vessel particulars for ferries on these routes.

Figure 5-5 shows an example of wake from a ferry inbound to Tsawwassen captured in satellite imagery.

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FIGURE 5-5: EXAMPLE WAKE PATTERN FROM BC FERRY INBOUND TO TSAWWASSEN

Figure 5-6 provides a comparison between vessel wakes from the Aframax Tanker and Escort Tug and a BC Ferry outbound from Tsawwassen. The ferry route is approximately perpendicular to the track of the outbound Aframax Tanker. The BC ferry adopted for the analysis is the Coastal Celebration (refer to Table 4-4) traveling at its service speed. Note that the pattern of the waves generated is very similar to the satellite image in Figure 5-5, verifying that the numerical methodology used is a good predictor of actual wake patterns.

It is very apparent in Figure 5-6 that the wake from the ferry dominates over that from the tanker and tug. At the navigation speeds assumed for the analysis, the wave period of wake from the tanker and tug will be on the order of 3 seconds, which is comparable to waves generated under conditions of light wind. The wave period associated with wake from the ferry is on the order of 5 seconds. The height of the largest ferry wake waves is around 1.7 metres from trough to crest.

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Metres

0 100 200 300 400 500

FIGURE 5-6: COMPARISON OF VESSEL WAKE FOR AFRAMAX TANKER AND ESCORT TUG WITH BC FERRY

Figure 5-7 provides an additional example of a BC Ferry transit crossing the track of the outbound Aframax tanker at an oblique angle. This is representative of a ferry on the route from Duke Point (Nanaimo) to Tsawwassen. The BC ferry adopted for the analysis is the Queen of Alberni (see Table 4-4) traveling at its service speed.

Again, it is apparent that the wake from the ferry dominates over that from the tanker and tug. At the scale shown, the wake from the tanker is nearly unnoticeable.

At the speeds assumed for the analysis, the wave period of wake from the tanker and tug will be on the order of 3 seconds, which is comparable to waves generated under conditions of light wind. The wave period associated with wake from the ferry is on the order of 5 seconds. The heights of the largest wake waves from the ferry are around 1.1 metres from trough to crest.

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Metres

0 100 200 300 400 500

FIGURE 5-7: COMPARISON OF VESSEL WAKE FOR AFRAMAX TANKER AND ESCORT TUG WITH BC FERRY

Figure 5-8 provides a comparison of wakes for the vessels considered based on the Kriebel (2005) analysis methodology. The results show that the wake from the Aframax Tanker (black line) and Escort Tug (yellow line) is diminutive, whereas the wake from the BC ferries is substantial.

The figure also provides a comparison of the vessel wakes with the ambient wave climate in the strait. The wave height corresponding to a Strong Wind Warning (20 knots) is about 0.65m, indicated by the light blue dashed line. Referring to Figure 4-3, waves of this height could be expected to occur in the Strait of Georgia about 10% of the time, or about 438 hours5 on average during a 6-month summer period from April to September. The results show that the ferry wake can approach and exceed most

5 Based on a total of 4,380 hours representing 6 months

Creative People, Practical Solutions.® Page 32 Attachment 9.1 TMEP Vessel Wake Assessment | Trans Mountain Pipeline ULC Revision A | October 29, 2018 ambient wave conditions. Wake from the tanker is negligible overall, while wake from the escort tug can range from around 0.8 metres right alongside the vessel to approximately 0.2 metres at a distance 300m away from the sailing line, well below ambient conditions for 20 knots.

Strait of Georgia 2.0 1.8 1.6 Aframax Tanker Tug 70 TBP 1.4 Queen of Alberni 1.2 Coastal Celebration 1.0 Strong Wind Warning 0.8

Wave Height (m) 0.6 0.4 0.2 0.0 0 50 100 150 200 250 300 Distance from Sailing Line (m)

FIGURE 5-8: STRAIT OF GEORGIA – COMPARISON OF VESSEL WAKES WITH AMBIENT WAVE CLIMATE

5.3. Haro Strait

Upon entering the Haro Strait, the escort tug will take up position tethered astern of the Aframax Tanker with a slack line to assist in case of a vessel malfunction. The transit speed through this area is reduced to about 10 knots. Figure 5-9 provides a plan view of the vessel wake computed using the Fourier-Kochin integration method over a 3 km × 3 km area. The basis of the analysis is summarized in Table 4-1 (Segment 3). Vessel particulars are summarized in Table 4-2 and Table 4-3.

The wake from the Escort Tug is barely noticeable in the figure, and the wake from the Aframax Tanker almost not discernible. The height of the largest of the wake waves from the tug is on the order of 0.3 metres from trough to crest and decrease rapidly in height with distance away from the sailing line.

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Metres

0 100 200 300 400 500

FIGURE 5-9: COMPUTED VESSEL WAKE FOR AFRAMAX TANKER AND ESCORT TUG

Haro Strait is another area where local ferries intersect the outbound transit line of the Aframax Tanker. This can occur in connection with Washington State Ferries traveling between Sidney and Anacortes.

Figure 5-10 provides a comparison with wake from a WSDOT ferry inbound to Anacortes. The ferry adopted for the analysis is the M/V Chelan (Table 4-4).

It is apparent from the results that the wake from the tanker and escort tug is negligible compared to the ferry wake, which is estimated to reach approximately 1 metre in wave height from trough to crest. The wave period associated with wake from the tanker and tug is estimated to around 2.7 seconds, while the wave period of the ferry wake is longer at around 4.2 seconds.

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Metres

0 100 200 300 400 500

FIGURE 5-10: COMPARISON OF VESSEL WAKE FROM AFRAMAX TANKER AND TUG WITH WSDOT FERRY

Figure 5-11 shows a comparison of wakes for the vessels considered based on the Kriebel (2005) analysis methodology. The results show that the wake from the Aframax Tanker (black line) and Escort Tug (yellow line) are negligible compared to the wake from the ferry and to ambient waves under 20 knots of wind.

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Haro Strait 1.2 Aframax Tanker 1.0 Tug 70 TBP Chelan 0.8 Strong Wind Warning

0.6

0.4 Wave Height (m)

0.2

0.0 0 50 100 150 200 250 300 Distance from Sailing Line (m)

FIGURE 5-11: HARO STRAIT – COMPARISON OF VESSEL WAKES WITH AMBIENT WAVE CLIMATE

5.4. Strait of Juan de Fuca

On the last leg of the transit before entering the Pacific, the Aframax Tanker makes its passage through the Strait of Juan de Fuca at about 12 knots transit speed. The basis of the analysis is summarized in Table 4-1 (Segment 4). During this passage the tanker is escorted by a large ocean-going tug.

Figure 5-12 provides a plan view of the vessel wake computed using the Fourier-Kochin integration method over a 3 km × 3 km area. The basis of the analysis is summarized in Table 4-1 (Segment 4). Vessel particulars are summarized in Table 4-2 and Table 4-3.

Compared to the previous results, the wake from the Escort Tug is somewhat more apparent because it is an ocean-going tug and larger in size. The wake from the Aframax Tanker is not discernible. The height of the largest of the wake waves from the tug is on the order of 0.5 metres from trough to crest and decrease rapidly in height with distance away from the sailing line.

The estimated wave period of the wake waves is on the order of 3.2 seconds, which is comparable to waves associated with light winds. Figure 5-13 shows that the ambient wave conditions in the Strait of Juan de Fuca are likely to drown out the vessel wake unless conditions are exceptionally calm. Referring to Figure 4-2, waves exceeding 0.2 m can be expected in the Juan de Fuca Strait about 81.5% of the time in winter months. Ambient wave action will progressively increase further as the tanker and tug head out to the open sea.

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Metres

0 100 200 300 400 500

FIGURE 5-12: COMPUTED VESSEL WAKE FOR AFRAMAX TANKER AND ESCORT TUG

Strait of Juan de Fuca 2.0 1.8 Aframax Tanker 1.6 Tug 110 TBP Strong Wind Warning 1.4 1.2 1.0 0.8

Wave Height (m) 0.6 0.4 0.2 0.0 0 50 100 150 200 250 300 Distance from Sailing Line (m)

FIGURE 5-13: STRAIT OF JUAN DE FUCA – COMPARISON OF VESSEL WAKES WITH AMBIENT WAVE CLIMATE

Creative People, Practical Solutions.® Page 37 Attachment 9.1 TMEP Vessel Wake Assessment | Trans Mountain Pipeline ULC Revision A | October 29, 2018 6. Discussion of Wake Effects

Project vessel wakes combine with the wakes created by other vessel traffic and with natural wind waves to create the overall sea state in a particular location. Typical wind and wave conditions at several places along the shipping route are discussed in Section 4.

The wave roses depicted in Figure 4-2 and Figure 4-3 indicate that the natural sea state is often calm or close to calm. Nonetheless, measurable winds persist in most places most of the time, so there is generally at least a slight surface chop, combined with residual waves that can persist for many hours after the wind state drops to calm.

Under such relatively calm conditions, some vessel-generated wakes (e.g. from ferries or even pleasure craft) could remain visible on the water surface for considerable distances (up to several km) from the vessel sailing line, before they eventually decay into ambient conditions. However, based on calculations in Section 4 and visual observations, Project vessel wakes generated by vessels traveling at typical speeds are likely to be negligible or even undetectable, even relatively close to the sailing line.

As an example, Figure 6-1 and Figure 6-2 show an Aframax tanker with two escort tugs underway near Second Narrows, on route to the Westridge Marine Terminal. The photographs were taken by the author on October 10, 2018. Environment Canada wind speed data from Vancouver Harbour are not available for that time period, but based on the author’s personal observation on that day, wind conditions were light, perhaps 5-8 knots, from the west. Under such light winds there was a slight ripple on the water surface but negligible wind waves. Yet even though the ambient wave conditions were essentially calm, the wakes generated by the tanker and the escort tugs are very small and barely visible, estimated to be less than 0.3m. The white water visible in the images is local propeller wash turbulence created in the immediate wake of the tug and tanker, but the radiated vessel wake (i.e. the portion that would propagate away from the sailing line and potentially affect other passing vessels or the shoreline), is very small. In fact, there is no visible wake radiating from the bow of the tanker at all, and the only radiating waves visible are associated with the tug rather than the tanker. This is consistent with the wave pattern predictions shown in Figure 5-1. In any case the height of the radiated wake is negligible.

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FIGURE 6-1: AFRAMAX TANKER WITH TWO ESCORT TUGS NEAR SECOND NARROWS, 2018-10-10

FIGURE 6-2: AFRAMAX TANKER WITH TUG HEADING TO WESTRIDGE MARINE TERMINAL, 2018-10-10

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6.1. Effects on Commercial Shipping

Deep sea vessel traffic and other commercial vessels such as tugs, ferries, fishing boats etc. are accustomed at being at sea in periods of high winds and substantial seas, including in open ocean conditions. The vessels and crews are typically well capable of navigating in such conditions. In comparison, and as shown above, vessel-generated wakes are generally small and insignificant relative to the routine sea states that commercial vessels are accustomed to. Given that Project vessel wakes are smaller and less frequent than many other types of vessel wakes already present in the region, and much smaller than routine sea conditions, it is expected that Project-related vessel wakes will have no appreciable impact on other commercial vessel traffic.

6.2. Effects on Recreational Craft

The effects of Project-related vessel wakes on recreational craft are difficult to quantify, in part due to the large range in sizes of recreational craft (both motorized and non-motorized) on the water, the range in skills and experience of operators, and lack of literature on the topic. Although there are numerous published safe boating guides that discuss the need for recreational boaters to reduce wake in designated “no wake zones”, as well as guidelines on how to reduce risk when crossing the wakes of other vessels, most of these studies focus on the impacts close to shore in relatively sheltered areas and inland waterways such as lakes and rivers, or within designated small craft harbours and marinas, rather than in open waters frequented by deep sea traffic.

There are also many wake prediction studies and publications in the field of naval architecture, but these mainly have to do with vessel design and means of optimizing hull form to improve stability, seakeeping ability, and to reduce radiated wakes, rather than the effect and management of those wakes on third parties or the environment.

There are also a number of studies that examine the (often substantial) wakes generated by high- speed passenger ferries, which have been known to create objectionable wakes in some places, including British Columbia waters. For example, BC Ferries once operated a series of high speed “Pacificat” catamaran ferries between Horseshoe Bay and Nanaimo in the 1990’s. These vessels travelled at speeds up to 34 knots, but shortly after they entered service there were numerous complaints about their large wakes (BCFC 2000). The large wakes ultimately necessitated a reduction in the vessels’ service speed, making it difficult for them to fulfil their operational goals of frequent, rapid transits. Because of this (as well as some other technical issues), the Pacificat ferries were soon decommissioned and sold.

Despite the number of vessel wake and wake management studies in the literature however, M&N is not aware of any publications that specifically examine the impact of wakes created by typical commercial cargo vessels such as tankers, nor quantify what “safe” limits for commercial vessel wakes are in open waters, nor even what size of wake might constitute a nuisance to others. The lack of scientific literature about cargo vessel wake effects suggests that the issue has not been deemed an important topic for research.

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In the absence of any widely recognized sources or guidelines that offer quantitative limits for commercial vessel wake impacts on small craft, this section discusses wave effects on recreational craft in qualitative or experiential terms.

Operators of recreational craft venturing into open water should ensure that their vessel is seaworthy, properly equipped, and that they have the necessary knowledge, training and certifications to operate their vessel safely. This obviously includes being prepared to handle the sea conditions that they are likely to encounter.

Transport Canada’s Safe Boating Guide6 contains safety tips and summarizes the regulations that pleasure craft operators must follow. Operators of motorized pleasure craft in Canada are required by law to carry proof of competency on board, such as the Pleasure Craft Operator Card or other recognized credentials. Anyone operating a pleasure craft in open waters where deep sea vessel traffic can be encountered (i.e. along the entire TMEP vessel route) can reasonably be expected to be competent in safe boating principles. Competency includes being familiar with the safe operation and maintenance of their vessel, required safety equipment, as well as being conversant with the typical conditions likely to be encountered (e.g. weather, tides, currents, waves, marked and unmarked hazards, shipping routes, other vessel traffic, etc. ). Furthermore, the Safe Boating Guide states that recreational boaters are expected to know where the shipping routes are, and to “be sure not to obstruct commercial navigation in commercial shipping channels.” This expectation is derived from the Collision Regulations7 which apply to all vessels, including pleasure craft, which state “a vessel of less than 20 metres in length or a sailing vessel shall not impede the passage of a vessel which can safely navigate only within a narrow channel or fairway”8. The implication is that boaters should expect to encounter and co-exist safely with large vessels in areas where these vessels are likely to be encountered (i.e. the established shipping lanes).

The Safe Boating Guide also includes guidelines about monitoring the weather. As discussed in Section 4.3, Environment Canada's Meteorological Service of Canada issues weather forecasts (in particular winds) over marine waters several times per day. Separate marine forecasts are provided for Juan de Fuca Strait, Haro Strait, Strait of Georgia, and Howe Sound, among other locations. While winds speeds can often be calm or negligible in any particular area on any given day, wind speeds less than the Strong Wind Warning (i.e. below 20 knots, or 37 km/h) would be considered “routine” conditions and easily handled by most competent recreational boaters who venture into open waters.

With wind speeds approaching the Strong Wind Warning threshold (i.e. up to 20 knots), substantial wave action9 can be expected depending on the location. In open water a 20 knot sustained wind will create whitecaps that could be dangerous to some small craft (e.g. a canoe or an open “car top” type boat), but would be considered routine for sailboats and larger power boats. The height of the generated waves at any location will depend on a number of factors including the wind speed, the

6 Transport Canada, 2014. TP511E, Safe Boating Guide – Safety Tips and Requirements for Pleasure Crafts, http://www.tc.gc.ca/media/documents/marinesafety/TP-511e.pdf accessed 2018-10-18

7 Collision Regulations, (C.R.C., c. 1416), as part of the Canada Shipping Act, 2001. 8 Collision Regulations, Rule 9 (b). https://laws-lois.justice.gc.ca/eng/regulations/C.R.C.,_c._1416/FullText.html accessed 2018-10-18 9 “Substantial” in this context is relative to typical small recreational vessels. Waves of this sort are small relative to deep sea vessels.

Creative People, Practical Solutions.® Page 41 Attachment 9.1 TMEP Vessel Wake Assessment | Trans Mountain Pipeline ULC Revision A | October 29, 2018 open water fetch distance, the duration of the strong winds, any local funnelling or sheltering effect created by high terrain (e.g. nearby mountains), the presence of any tidal currents, etc.

Table 4-6 shows the height and period of waves that can be expected to develop for a 20 knot sustained wind acting over open water fetches of varying distance. In the Strait of Georgia and Juan de Fuca Strait, the open water distances can range up to 70 NM or more, and 20 knot winds can produce waves of up to 1-2 m depending on the fetch. Haro Strait is somewhat more sheltered, with a maximum fetch of about 40 NM, but waves can still exceed 1m in some conditions. Within Burrard Inlet, open water fetches are limited to just a maximum of a few nautical miles. The largest wind waves that can be encountered in Vancouver Harbour are therefore “fetch limited” to perhaps 0.36 metres or less.

Waves in any of these locations can be amplified further in some circumstances. For example, when strong winds oppose a strong tidal current or rip, the resulting waves can become short, steep and breaking, posing a danger to some small craft. Similarly, waves can reflect off of steep rocky shorelines and when they interact with incoming waves moving in the opposite direction, their heights can combine or “superpose” to become even higher.

Prudent boaters know and understand the limitations of their vessel, their own skill, the skill and comfort of their passengers, and accordingly seek shelter in severe conditions. In all cases, the TMEP Project vessel wake effects are well under the limits that boaters can routinely expect to encounter in local waters, and therefore TMEP vessel wakes cannot reasonably be considered a significant safety or nuisance issue for boaters.

6.3. Anecdotal Experience

Some anecdotal insight into the significance of vessel wakes on recreational boaters can be gained through the author’s own personal experience. As a recreational sailor with over 30 years’ experience sailing in local waters (including the TMEP vessel route segments through Juan de Fuca Strait, Haro Strait, Boundary Passage, Strait of Georgia, English Bay, Burrard Inlet, Vancouver Harbour, First Narrows and Second Narrows) the author is very familiar with the nature of local sea conditions, including both natural wind waves and swell, tides, tidal currents, and the typical wakes generated by a wide range of commercial and private vessels.

In the author’s personal experience operating vessels ranging from kayaks and non-motorized sailing skiffs to auxiliary sailboats in the 10-20m range, wakes created by large deep sea commercial vessels have rarely if ever been a safety issue or even a nuisance issue. Even when large deep sea vessels such as container ships, grain ships or tankers interact with recreational craft in relatively close quarters (e.g. passing within First Narrows), the wakes generated by the deep sea ships are very small, often barely noticeable and quickly lost entirely in the ambient background waves. In places such as Vancouver Harbour, this is often because the vessels are moving relatively slowly and the Froude number (as discussed in Section 3.4) is small. In open waters, ship speeds are generally higher but wakes are usually still small compared to ambient conditions. Ships under escort (e.g. tankers) are generally slower than other types of commercial traffic, and correspondingly have smaller wakes compared to other ships such as container or grain ships. The images in Figure 6-1 and Figure

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6-2 depicting negligible tanker vessel wakes are entirely consistent with the author’s personal experience.

Passenger vessels such as BC Ferries vessels and cruise ships can produce a noticeable wake, however they often have a longer wavelength and lower steepness compared to typical wind- generated waves or pleasure craft wakes. Having a low steepness, the wakes of ferries and cruise ships are often experienced by boaters as being more like swell waves or “rollers” that might be encountered in the western portions of the Juan de Fuca Strait or the open ocean. These waves generally produce relatively gentle motions and accelerations in recreational craft, and are usually not objectionable.

Some tug boat wakes can be significant to boaters when tugs pass close by at speed. The waves close to a tug can be high enough or steep enough to create noticeable and even uncomfortable boat motions when they pass. Nonetheless, these conditions too are easily handled by experienced boaters. Maintaining a proper lookout for waves, and altering course and speed as needed (e.g. slowing down and/or heading into/away from the waves to reduce uncomfortable rolling motions) are routine and expected procedures that come naturally to most boaters.

In the author’s personal experience, the worst wakes from a boater’s perspective are usually caused by other recreational vessels, especially large “fast cruiser” displacement hull or semi-displacement pleasure craft which can create large, steep, breaking waves when they pass by at high speed. This effect is well known in the boating community, and it is considered good etiquette for such vessels to reduce their speed and wake when in close proximity to smaller, more vulnerable craft such as canoes or kayaks, especially in sheltered water. In sheltered harbours (e.g. False Creek) and around marinas, there are often established “no wake zones” that boaters are expected to observe. In open water, such as English Bay and the open straits, it is uncommon (and not expected) for vessels to reduce their speed to mitigate their wakes, and other boaters must be prepared for whatever they encounter.

Unlike commercial vessels which generally try to minimize wakes to save fuel, some recreational boats such as wakeboarding boats are designed to maximize their wakes to enhance the wake boarding experience. This too supports the author’s own experience that recreational craft create the largest and most objectionable wakes.

In summary, given that commercial shipping in general does not produce objectionable wakes to boaters, and the TMEP Project-related vessel traffic wakes are even smaller compared to other types of common commercial traffic, it is concluded that wakes from Project vessels will have negligible effect on the recreational boating community. The same conclusions can be extended to other relatively small vessels such as commercial fishing boats and water taxis, where the vessels can be similar in size to recreational boats (though usually operated by more experienced crew).

Creative People, Practical Solutions.® Page 43 Attachment 9.1 TMEP Vessel Wake Assessment | Trans Mountain Pipeline ULC Revision A | October 29, 2018 7. Conclusions

Through the numerical calculations, photographic evidence, and anecdotal experience presented in this report and other publications, the following conclusions can be drawn:

• The anticipated Project-related vessel traffic wakes will be similar to the vessel wakes created by the existing Westridge Marine Traffic, which have existed in local waters for many decades without generating any documented safety incidents or nuisance complaints.

• Vessel wakes from TMEP-related traffic are substantially smaller in height and substantially less in frequency of occurrence compared to existing and future commercial vessels (particularly ferries) operating along the same vessel routes. Therefore Project-related wakes are insignificant compared to other vessel wakes already present.

• M&N is not aware of any vessel wake issues caused in local waters by typical commercial deep-sea cargo vessels in general, including tankers.

• Vessel wakes from Project-related traffic are small or insignificant compared to naturally- occurring wind waves that occur frequently in local waters and are considered routine by most experienced boaters.

• The wake calculations presented herein use an updated methodology compared to the previous wake assessment results presented in Volume 8A of the Application [Ref a], resulting in generally similar numerical values for the predicted wakes. For example, the previous assessment predicted that tankers moving at a speed of 12 knots would create a wake of 0.16m measured 100m away from the sailing line. In comparison, the current study predicts wake height in the same conditions would be even less, at less than 0.05m. Similarly, the previous assessment predicted a tug wake at 12 knots and 100m to be 0.23m in height, whereas the current study predicts the corresponding height would be about 0.30m. These differences are within the level of accuracy expected for the methodology used and do not change the conclusions, namely that Project-related vessel wakes are small. Overall, the current results corroborate and support the previous results.

In summary, Project-related vessel wakes are expected to be very small and generally insignificant when compared to other types of natural and anthropogenic sources of waves already ubiquitous in the region. In M&N’s opinion, no specific mitigation measures are warranted to reduce, control or manage vessel wakes related to the TMEP Project.

Creative People, Practical Solutions.® Page 44 Attachment 9.1 TMEP Vessel Wake Assessment | Trans Mountain Pipeline ULC Revision A | October 29, 2018 8. References

a) Trans Mountain Pipeline (ULC). 2013. Trans Mountain Expansion Project Application for Certificate of Public Convenience and Necessity, Volume 8A – Marine Transportation

b) Moffatt & Nichol, 2013a. TMEP Application Volume 8C, TERMPOL Study 3.1 – Introduction

c) Moffatt & Nichol, 2013b. TMEP Application Volume 8C, TERMPOL Study 3.2 – Origin, Destination & Marine Traffic Volume Survey

d) Moffatt & Nichol, 2013c. TMEP Application Volume 8C, TERMPOL Study 3.5 – Route Analysis, Approach Characteristics and Navigability Survey

e) DNV 2013. TMEP Application Volume 8C, TERMPOL Study 3.15 – General Risk Analysis and Intended Means of Reducing Risks

f) EBA 2013. Meteorological and Oceanographic Data Relevant to the Proposed Westridge Terminal Shipping Expansion. TMEP Application Volume 8C, TERMPOL Supplementary Study S2.

g) Moffatt & Nichol (M&N). (2014a). “WMT Metocean Study Report.” Trans Mountain Expansion Project, Westridge Marine Terminal. Prepared for Trans Mountain Pipeline LP. TMP Report No. 01-13283-TW-WT00-MD-RPT-0004 RA.

h) BCFC (2000). Fast Ferry Program – Wake and Wash Project. Report prepared by Sandwell Engineering for the British Columbia Ferry Corporation. Final Report, August 2000.

i) CEM (2006). Coastal Engineering Manual. Engineer Manual EM 1110‐2‐1100 (Part II), Chapter 7, Harbor Hydrodynamics. U.S. Army Corps of Engineers, 1 June 2006 (Change 1).

j) Kriebel, D.L. and Seelig, W.N. (2005). An Empirical Model for Ship‐Generated Waves. Proceedings of the Fifth International Symposium on Ocean Wave Measurement and Analysis. 2005.

k) Maynord, Stephen T. (2005). Wave height from planing and semi‐planing small boats. River Research and Applications 21:1-17 January 2005.

l) Revathi et al. (2012). C. Revathi, and M.K. Khan. Theoretical Ship Wave Pattern Resistance Evaluation Using Kochin Wave Amplitude Function. International Journal of Innovative Research & Development. ISSN: 2278‐0211 (Online). Vol. 1, Issue 10 (Special Issue). www.ijird.com. December, 2012.

m) Schierech, G.J. (2001). Introduction to Bed, Bank and Shore Protection. Delft University Press.2001.

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n) Tuck et al. (2001). E.O. Tuck, D.C. Scullen and L. Lazauskas. D.C., Ship‐Wave Patterns in the Spirit of Michell. IUTAM Symposium on Free Surface Flows. Fluid Mechanics and Its Applications, Volume 62, 2001, pp 311‐318.

o) Tuck (2003). E.O. Tuck. Computation and Minimisation of Ship Waves, in Applied Mathematics Entering the 21st Century. Invited Talks from the ICIAM 2003 Congress. Edited by: James M. Hill, University of Wollongong, New South Wales. Edited by: Ross Moore, Macquarie University, Sydney. ISBN: 9780898715590. Academic and Professional Books. Cambridge University Press.

p) US Army Corps of Engineers (USACE), 2002. Coastal Engineering Manual, EM_1110-2- 1100.

q) Verhey et al. (1989). H.J. Verhey and M.P. Bogaerts. Ship waves and the stability of armour layers protecting slopes. Delft Publication number 428. Delft Hydraulics, November 1989.

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Moffatt & Nichol, Vancouver Suite 301 - 777 West Broadway Vancouver BC V5Z 4J7 Canada T +1 604-707-9004

www.moffattnichol.com Creative People, Practical Solutions.® Page 47 Attachment 9.1