www.terrahdd.com

ENGINEERING ENVIRONMENT GEOTECHNICAL CONSTRUCTION-SUPERVISION

Project: 2021 NGTL System Expansion Project

Document Title: HDD Feasibility Report - Mcleod River Crossing

Report Number: 00796-THD-C-RP-0013_2020-09-09 Rev No Description Rev Date Originator Reviewer Approver

0 ISSUED FOR USE SEPT. 09 2020 PL/PP SG/PP/BR SG

TerraHDD SOLUTIONS INC. “Your Trenchless Solutions Provider”

1 INTRODUCTION ...... 3 Table of Contents 2 SCOPE OF WORK ...... 3 3 GEOTECHNICAL/GEOPHYSICAL PROGRAM ...... 4 GEOTECHNICAL INVESTIGATION ...... 4 GEOPHYSICAL INVESTIGATION ...... 6 GROUNDWATER ...... 6 4 SITE CONDITIONS AND HDD DESIGN SUMMARY ...... 7 5 HDD DESIGN CRITERIA ...... 8 DESIGN BASIS ...... 8 BORE GEOMETRY AND ALIGNMENT CONSIDERATION ...... 8 ENTRY AND EXIT ...... 8 VERTICAL DESIGN RADIUS ...... 9 INSTALLATION DEPTH ...... 10 LENGTH ...... 10 HDD BORE SIZE ...... 10 CASING ...... 10 BUOYANCY ...... 11 WASTE VOLUME AND SOURCE WATER ASSESSMENT ...... 11 DRILLING SCHEDULE ...... 12 WORKSPACE AND STAGING AREA ...... 12 STEERING CONTROL ...... 12 6 HDD EVALUATION ...... 13 PIPELINE PARAMETERS ...... 13 PIPE WALL THICKNESS ...... 13 PULLING LOAD & STRESS ANALYSIS ...... 13 ANNULAR PRESSURE (HYDROFRACTURE) CALCULATION ...... 18 7 BREAK-OVER (PIPE LIFTING SUPPORT) ...... 22 8 CROSSING SPECIFIC RISKS AND MITIGATION MEASURES ...... 23 FRACTURED BEDROCK ...... 23 CASING INSTALLATION ...... 23 PIPELINE DRAG SECTION ...... 23 LOSS OF CIRCULATION OR FLUID RELEASE ...... 23 NOISE AND TRAFFIC CONTROL ...... 24 9 OTHER RISKS AND MITIGATION MEASURES ...... 24 10 CROSSING CONTINGENCY ...... 25 11 CONCLUSION ...... 26

APPENDIX 1 HDD DESIGN DRAWING

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd.

1 INTRODUCTION

Nova Gas Transmission Ltd. (“NGTL”), a wholly owned subsidiary of TC Energy, proposes to construct, own and operate new pipeline facilities in that will form an integral part of the existing NGTL System. These facilities are referred to as the 2021 NGTL System Expansion Project. The Project includes approximately 345km of 1,219mm (NPS 48) pipeline, valve sites, pipeline tie-ins, three compressor unit additions, and one control valve. The proposed pipeline additions are in eight sections that will loop existing NGTL System mainlines.

Six (6) high-priority anticipated trenchless crossings have been identified for this project, including:

• • Little Smoky River • McLeod River • • North • Wapiti River

TerraHDD Solutions Inc. (TerraHDD) was retained to complete a Horizontal Directional Drill (HDD) final feasibility study based on the geotechnical conditions for all crossings excluding Little Smoky River & Wapiti River. Preliminary feasibility assessment of the selected trenchless method has been conducted for the crossings in June 2018.

The survey information for this project was provided by Midwest surveys Inc. (Midwest) and the geotechnical investigation was carried out by Golder Associates Ltd. (Golder). Based on these available data TerraHDD conducted HDD design and this engineering feasibility report for Mcleod River Crossing.

2 SCOPE OF WORK

The scope of work for the engineering feasibility evaluation includes:

• Horizontal Directional Drill design based on provided alignment • Annular pressure calculation based on geotechnical conditions • Break-over Design • Final engineering feasibility report addressing the viability of the HDD installation at the crossing location and presenting potential construction related concerns • Design report

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 3 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. 3 GEOTECHNICAL/GEOPHYSICAL PROGRAM

As part of the HDD feasibility evaluation process Golder has completed geotechnical and geophysical investigations, specifically to provide information for the crossing methodology at this location. Refer to geophysical survey and geotechnical reports (00796-GAL-C-RP- 0005_Rev 0 & 00796-GAL-C-RP-0018_A) issued by Golder for the Mcleod River Crossing for detailed geotechnical investigation results at the crossing. GEOTECHNICAL INVESTIGATION A total of five (6) geotechnical boreholes were drilled. There were two drilling program that took place for this crossing. The first drilling program drilled five boreholes from May 08 through May 23, 2019 with two boreholes (MR19-HDD-BH01, and BH02) on the South side of the crossing and the other two boreholes (MR19-HDD-BH03 and 04) on the North side of the crossing. The fifth Borehole MR19-HDD-BH04A was drilled adjacent to the MR19-HDD-BH04 to gather additional overburden sample. As a result, both boreholes had similar result so only MR19-HDD-BH04 is shown on the HDD drawing and is addressed in this report. The second drilling program consisted of drilling a single borehole (MR20-HDD-BH-01) by the new entry location. This was drilled between July 13 to July 16, 2020. Table 1 highlights borehole ID, surface elevation, bedrock depth and termination depth. Table 1: Borehole Summary

Surface Bedrock Termination BH ID Elevation Depth Depth

MR19-HDD-BH01 901.2m 4.6m 41.2m

MR19-HDD-BH02 901.6m 6.3m 55.1m

MR19-HDD-BH03 915.7m 19.9m 80.2m

MR19-HDD-BH04 917.4m 21.7m 57.9m

MR20-HDD-BH-01 917.8m 24.8m 29.3m

Borehole MR20-HDD-BH01 is the closest borehole to the entry location of the proposed HDD, located on the south side of the crossing. The borehole report shows that the surficial material is a soft silty clay layer down to a depth of 8.1m followed by sandy silty clay (till) with a trace of gravel and coal to a depth of 23.4m. The sandy silty clay (till) is cohesive and firm to very stiff. Beneath this overburden, the borehole encountered completely weathered mudstone (possibly bedrock) to a depth of 24.8m. Bedrock (weather siltstone, sandstone and mudstone) was encountered to the end of the 00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 4 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. borehole at depth of 29.26m. A casing was set to 10.8m below grade to restrict water flow into the borehole and prevent borehole sloughing as the soft clay was caving into the borehole. Due to the drilling method of solid stem auger, the information of bedrock’s weathered conditions, strength and RQD are not available. It is anticipated that the upper bedrock may be highly fractured and loss of fluid circulation during HDD construction. Groundwater seepage was observed at 2.4m below grade during drilling and groundwater level was measured at 0.9m below grade upon completion of borehole drilling.

Borehole MR19-HDD-BH01 is the closest borehole to the toe of slope located on the south side of the crossing. The borehole report shows that the surficial material is a silty clay layer down to a depth of 1.5m and then silty sand down to the 3.5m. The silty clay was non-cohesive and consisted of fine sand with some fine gravel which were loose to compact. Beneath the silty sand layer, the borehole encountered siltstone and mudstone with intermittent layers of sandstone. The bedrock was weak to medium strong and was slightly to moderately weathered bedrock. The depth of this borehole is 41.2m. The rock quality designation (RQD) of the bedrock generally ranged between 52% to 100% except for 38% to 50% from 6.1m to 12.2m, and 32% from 22.9m to 24.4m. The RQD at the end of the borehole is 100%. The HDD drill path will be about 19m below the end of the borehole. Drilling fluid circulation of about 5% was observed below 32m to 41.1m during drilling the borehole. Groundwater seepage was not observed during drilling.

Borehole MR19-HDD-BH02 on the south bank of the crossing was drilled about 135m north from the borehole MR19-HDD-BH01 to a depth of 55.1m. The borehole shows that the surficial layer of sandy silty clay/clayey sand/silty sand/silty clay/sand extends to a depth of 5.9m. These layers encountered fine to medium sand with trace of gravel at certain depth. Underneath this layer, the borehole encountered from 5.9m to 55.1m of bedrock, mainly siltstone and mudstone with intermittent layers of sandstone. The bedrock was mainly weak to medium strong and was slight to moderately weathered bedrock. The RQD of the bedrock generally ranged between 58% to 100% except for 40% from 10.7m to 12.2m, 47% from 16.8m to 18.3m, 35% from 24.4m to 25.9m, and 40% from 33.5 to 35.1m. The RQD at the end of the borehole is 100%. The HDD drill path will be about 12m below the end of the borehole. Drilling fluid circulation of 0% was observed between 51.8m to 55.1m during drilling the borehole. Groundwater seepage was not observed during drilling.

Borehole MR19-HDD-BH03 is located on the north side of the crossing about 110m of North of Mcleod River. The borehole shows that the surficial layer of silty clay/sandy silty clay/clayey sand/silty clay and sand extends to a depth of 18.7m. These layers encountered fine sand and gravel. Underneath this layer, the borehole encountered bedrock to depth of 79.2m, mainly mudstone and siltstone with intermittent layers of sandstone. The bedrock was weak to medium strong and was slightly to moderately 00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 5 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. weathered bedrock. The RQD of the bedrock generally ranged between 58% to 100% except for 32% from 19.8m to 21.3m, and 40% from 21.3m to 22.9m. The RQD at the apparent intersection of the borehole and the HDD drill path at depth of 56m is 100%. Drilling fluid circulation of 0% was observed below 38.1m to 80.2m during drilling the borehole. Groundwater measured at 4.6m below grade during overburden drilling.

Borehole MR19-HDD-BH04 is located on the north side of the crossing, and is 145m northwest of the exit point. The borehole results show that the surficial layer is a 21.6m depth of silty clay which was cohesive and consisted of fine sand and trace of gravel with soft to hard consistency. Following this layer, the borehole encountered bedrock to a depth of 57.9m. It consisted of mudstone and siltstone with intermittent layers of sandstone. At multiple depths completely weathered bedrock was observed. The RQD of the bedrock generally ranged between 56% to 100% except for 43% from 32m to 33.5m, and 13% from 41.1m to 42.7m. Drilling fluid circulation of 25% was observed from 38.1m to 57.9m during drilling the borehole. The borehole is 145m away from the exit point. There will not be apparent intersection between the borehole and the HDD drill path. Groundwater seepage was observed at approximately 5.0m below grade during overburden drilling.

Borehole data produced by Golder indicates a general stratigraphic profile of topsoil, clay, silty clay, clayey silt, sand and bedrock (interbedded sandstone, siltstone, and mudstone). Golder’s 2019 & 2020 geotechnical report, including borehole logs, for the Mcleod River crossing includes detailed description of soil and bedrock conditions.

GEOPHYSICAL INVESTIGATION Golder has conducted two geophysical investigations for the Mcleod River HDD crossing. The field work for the investigations were conducted on May 11 - 15, 2019 and July 13 - 16, 2020, and consisted of collecting Electrical Resistivity Tomography (ERT) data and Seismic Refraction Tomography (SRT) data.

The interpreted overburden thickness ranged from approximately 3 to 25m. Overburden thickness at the exit point is about 19m. Overburden thickness at the entry point is about 22m, and consisted of clay, silty clay, sand, and trace gravel. Soils near the HDD exit consist predominantly of fine-grained silty clay till. Soils near the HDD entry are clay and sandy silty clay.

GROUNDWATER No standpipe piezometers were installed during the field program. Groundwater levels are inferred from observations made during drilling. Groundwater seepage was observed at approximately 5.0m below grade during overburden drilling near the proposed HDD exit point. Groundwater seepage was observed at 2.4m below grade during drilling and

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 6 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. groundwater level was measured at 0.9m below grade upon completion of the borehole drilling Detailed information on groundwater can be referenced in Golder’s 2019 and 2020 geotechnical reports.

The conclusion from the results of the current geotechnical and geophysical investigation is that, from this perspective, an HDD at this location is technically feasible. Circulation losses would be anticipated by the HDD contractor. The use of appropriate loss control materials shall be considered. It is recommended that the geotechnical report be provided to the contractors for their planning purposes.

4 SITE CONDITIONS AND HDD DESIGN SUMMARY

The crossing overview and the HDD design are shown in Figure 1 and on the HDD Design Drawing in Appendix 1. At the crossing location, the Mcleod River consists of a single channel that is approximately 75m wide and is about 2m deep. In the crossing area, the McLeod River channel meanders in an approximately 350m wide valley bottom. The north valley slope is over 25m high at the crossing location. On the south side of the river channel along the pipeline route, the valley bottom is about 220m wide and about 14m higher than the river channel and top of the slope is about another 14-15m higher than the valley bottom. The hydrotechnical report specifies the scour depth at the crossing location is about 3.4m based on 100-year discharge. The pipeline alignment runs south to north. The HDD design entry is located on the south side of the crossing and the exit is located on the north side of the crossing. The drag section for this crossing is located on the north end of the crossing along the ROW and temporary workspace.

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 7 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd.

Previous N Trenchless Crossing Alignment Current HDD Crossing Alignment Existing Pipeline ROWs

Figure 1: LiDAR Image showing a crossing area The proposed HDD profile has a total measured drill length of 1,051m and a horizontal drill length of 1,033m. The depth of the cover beneath the Mcleod River thalweg is approximately 50m and min. cover underneath the water bank edge is about 48m. A horizontal tangent of about 15m has been designed prior to steering upward.

5 HDD DESIGN CRITERIA

DESIGN BASIS Codes and Standards are followed for the design of this crossing: • CSA Z662-19 Oil and Gas Pipeline Systems • PRCI – Installation of Pipelines by Horizontal Directional Drilling, An Engineering Design Guide PR-277-177507-E01, September 2015 • ASCE – Pipeline Design for Installation by Horizontal Directional Drilling • TEN-ME-HDD-GL HDD Design and Construction standard, Client’s Specification BORE GEOMETRY AND ALIGNMENT CONSIDERATION ENTRY AND EXIT The entry and exit location for this crossing are shown in Figure 2 and were highly dependent on the topography of the crossing, ROW limits and the geometry of the drill.

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 8 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd.

N

Figure 2: HDD Alignment and Entry/Exit Location

For horizontal directional drills, it is preferred to have the entry location at lower elevation in relation to the exit location of the drill. This is beneficial as gravity will assist in bringing the drilling fluid back to the entry side for cleaning and recirculating. For this design, the HDD entry is located on the south side and the HDD exit is located on the north side of the crossing. The entry was initially located in the valley bottom at the south of the crossing, however, it was relocated to the top of the slope and passed the dirt road due to the landowner request. The elevation difference between the entry and is exit is negligible. A 16˚ angle is selected for the HDD entry and 13˚ is selected for the HDD exit at this crossing. When considering such large diameter pipe, it is good to have lower entry and exit angles so that it will ease during the tie-in process and pullback. However, due to the ROW and site restrictions and cover requirement underneath the river, the entry and exit angles are steeper than normal. VERTICAL DESIGN RADIUS For horizontal directional drill, the product pipe is pulled through the borehole which has a radius of curvature above the minimum allowable bending radius for the product pipe. This is to ensure that the product pipe can be safely bent during construction and subsequent operation stages. The minimum product pipe bending radius based on the pipe specifications in Table 3 is calculated to be 890m. This is determined by limiting the maximum shear stress to 45% of SMYS under all the loads combined scenario. This is the theoretical curve radius that the pipeline can be safely operated during installation and operation. A standard HDD curve radius of 1,400m, a single joint radius of 950m and a three Joint radius of 1,100m has been designed for the crossing.

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 9 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. INSTALLATION DEPTH The HDD installation depth depends on several factors such as the soil and bedrock, underground conditions, drilling fluid annular pressure, design radius, drill length, casing length, and the presence of existing structures, utilities and pipelines. Along with the above mentioned factors, the depth for a HDD highly depends upon the overburden materials above the drill path. This is to ensure that the overlaying material will provide sufficient pressure against the required HDD fluid pressure to remove the cutting and maintain the bore stability over the course of installation. The HDD installation depth at this crossing has been designed with a cover depth of about 50m underneath the river thalweg as shown in the Appendix 1. The annular pressure analysis illustrated in section 6.4 shows the HDD is feasible from the perspective of the cover depth designed. LENGTH The geometry of the HDD drill path depends on the topography, geology, surface casing length, workspace, drilling method utilized and overhead and underground existing obstructions at the crossing. Based upon the provided elevation profile at the Mcleod River crossing, the horizontal drill length is approximately 1,033m and the total drill length is about 1,051m as shown on the drawing in Appendix 1. HDD BORE SIZE The final HDD bore size is required to be larger than the pipe to be installed which allow the drilling fluid to circulate back to the entry or exit locations. This permits displacement of any cuttings that are still in the borehole, and reduces the probability of pipe getting stuck in the HDD Bore. Typical industry standards (and “Rule of Thumb”) are followed when determining the HDD Bore size. In some instances it is necessary to increase the borehole diameter above the typical industry standards to allow for unfavourable hole conditions such as cobbles, boulders or fractured rock or to allow more space at suspected deviations in the borehole. The final HDD bore size recommended for the Mcleod River drill is 1524mm (60”). This size may increase depending on the drilling conditions and the condition of the hole during drilling. The drilling contractor on site will assess the site conditions and determine the final HDD bore size during drilling operation based on site specific conditions. As noted in this report, casing is recommended to be installed at the entry of the drill. Casing diameter shall be large enough to accommodate the final bore size. CASING The casing is anticipated to be used at the HDD entry to support the stability of the HDD bore through the near surface soft soils and/or coarse grained soil, such as loose sand and gravel. Casing size needs to be big enough to accommodate final reamer size. The recommended final HDD bore size is 60in. (1,524mm) in diameter for the NPS 48 (1,219mm) pipeline. Casing would be recommended to be 72in. (1,829mm) at a minimum. Telescoping

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 10 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. casing shall be considered for casing lengths of greater than 50m based on TEN-ME-HDD-GL standard. Borehole MR20-HDD-BH01 shows the top layer is soft clay with a depth of 8.1m. A casing was set to 10.8m below grade to restrict water flow into the borehole and prevent borehole sloughing as the soft clay was caving into the borehole. In order to prevent HDD hole collapse, an up to 50m casing has been designed at the entry side. The entry casing is to prevent hole collapsing during HDD drilling at the entry side. On the exit side, if a surface casing is required, contractor shall submit a surface casing plan to TC Energy for approval prior to construction. A centralizer shall be used to reduce the risk of catching the reamer at end of the casing during pipe pullback and reaming. It is suggested that contractor may prepare a longer casing in case required. BUOYANCY In HDD design, the buoyancy control evaluation is normally recommended for large diameter pipeline. Implementing buoyancy control in such cases will reduce the pulling load required during the pullback process and reduce potential coating damage due to pipe riding up against the top of the bore hole. For this crossing in order to keep installation stresses within the limit the buoyancy control plan is typically required to be generated by the pipeline support contractor prior to pullback. This plan will assist the contractor with what equipment and materials are required at the site, and provide other information such as an equipment layout for construction. At the Mcleod River crossing, stress on the pipe will be reduced during installation when buoyancy control is introduced. The buoyancy control will require 1051m of product pipe to be completely filled with water. As a result, the pulling load will be 236,000lbs without a safety factor and 354,000lbs with a 1.5 safety factor. For detail pulling load and stress evaluation, refer to section 6.3. WASTE VOLUME AND SOURCE WATER ASSESSMENT The estimated amount of waste volume and source water assessment for this HDD are provided in Table 2. Table 2: Waste volume and source water assessment

SOLIDS 3,197 m3 FLUIDS 5,308 m3 TOTAL WASTE PROFILE 8,505 m3 SOURCE WATER 8,000 m3

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 11 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. DRILLING SCHEDULE Construction of the NPS 48 (1219 mm OD) crossing may require an estimated schedule of 20 weeks of drilling based on work of 24 hours a day and 7 days a week. HDD construction schedule includes the activities shown in table below.

Days (1) Mobilize 2 Pilot Hole 11 Ream 24" 13 Ream 36" 18 Ream 48" 26 Ream 60" 52 Wiper 2 Pull Line 2 Demobilize 2 Contingency 13 Total estimate 141 (20 Weeks) (1) Schedule is based upon typical meterage per day estimates. Schedule for casing installation can be individually assessed by contractor on a crossing by crossing basis and is not included in this estimate.

WORKSPACE AND STAGING AREA The workspace and ROW on the north side of the crossing will provide the staging area for a single drag section.

North of the break-over section, the pullback passes over an unnamed tributary. There is a notable elevation change across this tributary which is not shown on the pullback drawing, which shall be considered by the contractor during pipe laydown and pipe pull. STEERING CONTROL Extremely soft/hard formations or sudden changes in geological formations can lead to steering difficulties. This occurs when the formation does not provide adequate resistance to the bit to allow it to build a change in direction. At this crossing location, the underlying bedrock is much harder than the overburden soils, but the 1400m design radius, comparing the minimum calculated 890m, has provided adequate tolerance for drilling, and nonetheless every effort shall be made to ensure the design and IFC radius guidelines are followed during the drilling of the pilot-hole.

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 12 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. 6 HDD EVALUATION

PIPELINE PARAMETERS The pipeline specifications for this crossing were provided by NGTL and these specifications have been summarized in Table 3. Table 3: Pipe Specifications

OUTER DIAMETER (OD) 48 inch 1219 mm WALL THICKNESS 1.00 inch 25.4 mm PIPE GRADE 70,000 psi 483 MPa CATEGORY II II INSTALLATION TEMPERATURE 14 ˚F -10 ˚C MINIMUM OPERATING TEMPERATURE 23 ˚F -5 ˚C MAXIMUM OPERATING TEMPERATURE 120 ˚F 49 ˚C MAXIMUMINSTALLATION OPERATING TEMPERATURE PRESSURE (MOP) 1,260 psi 8,690 kPa MEDIUMMINIMUM CARRIED TEMPERATURE Natural Gas

PIPE WALL THICKNESS The pipe wall thickness required for HDD crossing tends to be greater than the wall thickness required for trench design. As the product line is pulled through a curved borehole, the pipe deforms elastically. This imparts additional stress on the pipe and therefore it requires a higher wall thickness to withstand the internal operating pressure of the pipeline. The 25.4mm wall thickness was assessed and meets the stress criteria for operation and installation for this crossing. See the stress calculation spreadsheets for detail. PULLING LOAD & STRESS ANALYSIS Calculation results of stress analysis and pipe pulling load for with and without buoyancy control are shown in spreadsheets below. The provided pulling load is theoretical and calculated based on the PRCI 2015 methodology. The allowable stresses were based on the references from PRCI 2015 and CSA Z662-19.

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 13 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd.

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 14 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd.

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 15 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd.

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 16 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd.

The result from the stress analysis confirms that the current design satisfies the installation stresses (Tensile stress, bending stress, hoop stress, and combined longitudinal stresses) and the operational stresses (Bending stress, hoop Stress, thermal stress, net longitudinal stress and shear stress).

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 17 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. The maximum operation longitudinal stress calculated (compressive) is 32,742psi. The maximum installation longitudinal stress (tensile) is 34,591psi, and 51,887psi (with a safety factor of 1.5). It should be noted that the pulling load calculated for this crossing is 981,000lbs without buoyancy control and 236,000lbs with buoyancy (NPS 48 pipe shall be completely filled with water for the full length of 1051m). The pulling load with buoyancy and a safety factor of 1.5 is 354,000lbs. More details regarding buoyancy control is further provided in section 5.4. A minimum drill rig size of 880,000lbs pull/push force is recommended at the entry side in order to complete the pilot hole drill and pull the product line in and through the borehole. The rig size recommended is based on buoyancy control. The pulling load provided is not supposed to be used as a sole factor for selecting the drill rig for drilling. It is recommended that the drilling contractor assess the crossing independently based on drill rig capacity, and the torque force capability. A minimum drill rig size of 440,000lbs pull/push force is recommended at the exit side to assist with reaming the hole to the final bore size. ANNULAR PRESSURE (HYDROFRACTURE) CALCULATION Hydrofracture is a phenomenon that occurs when drilling fluid pressure in the annular space of the drilled hole exceeds the confining strength of the surrounding soils, resulting in deformation, cracking, and fracturing. The fractures may then serve as flow conduits for drilling fluid allowing the fluid to escape into the formation and possibly up to the ground surface. Drilling fluid that makes its way to the ground surface is known as an inadvertent drilling fluid return or, more commonly, a “frac-out.” Ideally, the path of least resistance is through the annulus of the drilled hole and back to the fluid containment pit at the HDD entry point. However, the path of least resistance may also be through naturally occurring subsurface features such as fissures in the soil, shrinkage cracks, or porous deposits of gravel. Drilling fluid may also flow to the surface alongside piers, piles, utility poles, or other structures. The risk of hydrofracture can be determined by comparing the formation limiting pressure (confining capacity) of the subsurface to the estimated annular pressure associated with HDD operations. If the anticipated drilling fluid pressure in the annulus exceeds the confining capacity of the subsurface, there is risk that inadvertent drilling fluid returns due to hydrofracture will occur. As part of the site-specific assessments for the HDD, formation limiting pressures were calculated and compared to estimated annular pressures necessary for HDD operations. Results are summarized in both tabular and graphical format. The confining capacity of the subsurface was calculated using methods of Delft Geotechnics approach as outlined in Appendix A of Guidelines for Installation of Utilities beneath Corps of Engineers Using Horizontal Directional Drilling. The predicted drilling fluid annular pressure was calculated by using procedures outlined in the Horizontal Directional Drilling

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 18 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. Good Practices Guidelines, third edition, and principle authors: David Bennett and Samuel T, Ariaratnam, in 2008. In order to reduce the risk for fluid releasing to surface, contractor may use an ‘intersect’ installation method for this crossing. Since an ‘Intersect’ installation method may be required at the crossing, the AP charts are calculated from both the South Entry to North Exit (Graph 1) and from the North Exit to South Entry (Graph 2), which are shown below. The calculated fracture pressure is displayed on the graphs with a safety factor of 1.6. Geotechnical parameters for the annular pressure calculations were derived from the Golder’s geotechnical reports. The following set of parameters are used for the Annular Pressure (AP) calculations: Annular Pressure Parameters:

Unit weight (Bedrock): 2,245 kg/m3 Unit weight (Entry and exit overburden): 1,939 kg/m3 Internal friction angle (Bedrock): 30⁰ Internal friction angle (Entry side overburden): 27.5⁰ Internal friction angle (Exit side overburden): 26.6⁰ Effective cohesion (Bedrock): 0 kPa Effective cohesion (Entry side overburden): 2.5 kPa Effective cohesion (Exit side overburden): 3.75 kPa Shear modulus (Bedrock): 40 MPa Shear Modulus (Entry side overburden): 5.75 MPa Shear Modulus (Exit side overburden): 9.25 MPa Poisson’s ratio (Bedrock): 0.2 Poisson’s ratio (Entry side overburden): 0.4 Poisson’s ratio (Exit side overburden): 0.5 Plastic zone radius: 0.933m (Three (3) times pilot hole diameter, as per TC Energy’s requirement) Fluid density: 1180 kg/m3 Fluid flow rate: 2 m3/min Plastic viscosity: 25 cp Yield point: 28 lb/100 ft2 Pilot hole size: 12 1/4” Drill stem size: 6 5/8” A = 0.054 m²

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 19 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd.

GRAPH 1: GRAPH

Annular PressureAnnular from

the South EntrySouth the NorthExit to

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 20 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd.

GRAPH

2

:

Annular PressureAnnular thefrom

North North Exit

to

South Entry South

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 21 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. The current HDD drill path under the Mcleod River is about 50m, but the overburden pressure is still below the minimum required annular pressure under the river. Generally, it’s the calculated fracture pressure line on AP graph that is to be used to weigh the risk of inadvertent drilling fluid release, which is higher than the zone of the allowable construction annular pressure. Therefore, from the annular pressure analysis, the HDD is feasible.

7 BREAK-OVER (PIPE LIFTING SUPPORT)

Pipeline of such large diameter will require lifting support during pipe pullback. North of the break-over section, the pullback passes over the unnamed tributary. There is a notable elevation change across the tributary which is not shown on the break-over drawing, which shall be considered by the contractor during pipe laydown and pullback.

To avoid pipe being over-stressed during the pullback process, the minimum radius of the curved section of the pipe and the specific lifting heights have been calculated. The lifting program was calculated by iteration of cantilever bending with natural sag as the basis to reach the exit angle. The 4” HDPE fill line for buoyancy control is assumed to be full of water within the entire length of the pullback section and is considered in the break-over design calculation.

The Break-over radius does not need to take into account the operational conditions such as temperature and pressure, therefore the minimum vertical curve radius was determined to be 630m. This also satisfies the requirement of section 7.10.7 of TEN-ME-HDD-GL standard. The highest lifting point shall be about 19m based on the 13 degree exit angle and the grade provided by client. Contractor shall field fit lifting and support equipment on site based on grade conditions encountered. An initial pull force before entering the HDD borehole is approximately 175,614lbs.

The maximum bending stress for the break-over is 33,402psi and tensile stress is 1,190psi. Considering this bending and tensile stresses, the maximum longitudinal stress is 49.4% of SMYS.

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 22 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. 8 CROSSING SPECIFIC RISKS AND MITIGATION MEASURES

FRACTURED BEDROCK Fractured bedrock were reported in the geotechnical report and circulation loss of drilling fluid was encountered during drilling of all five (5) geotechnical boreholes. If fractured bedrock encountered, it can cause loss of circulation to surface and waterbody. Therefore, drilling fluid circulation loss will be expected during HDD construction. Engineering Drilling Fluid Management Plan shall be in place. For details regarding reducing the risk of loss of circulation and Emergency response plan, please refer to section 6.2 and 6.3 in the HDD Design report 00796-THD-C-RP-0009_2020-07-23. CASING INSTALLATION A 50m long entry casing is currently designed to prevent HDD hole collapse and shown in the HDD design drawing. To install the 50m casing of minimum 72” OD could be a great challenge. Final casing length required will be up to the contractor to decide and to make sure that the casing is set into competent formation. Contractor shall provide a casing installation and extraction plan with bid document to TC Energy for evaluation during bid process. PIPELINE DRAG SECTION North of the break-over section, about 700m from exit point the pullback passes over the unnamed tributary. There is a notable elevation change across the tributary which is not shown on the break-over drawing, which shall be considered by the contractor during pipe laydown and pullback. It is understood that the pipe laydown will be in one section and will be able to cross over the unnamed tributary. If in the case, the pipe laydown needs to be laid down prior to the creek, it will need to be split into two sections. This typically increases the risk of stuck pipe, so it is important to have a single string for the drag section. LOSS OF CIRCULATION OR FLUID RELEASE The risk of fluid loss is higher during pilot hole drilling than during the reaming process, due to the smaller annular space of the pilot-hole. The HDD path has been designed to minimize the potential for a frac-out with adequate cover to withstand drilling pressures as shown on the pressure charts (See section 6.4). Due to the entry and exit location restrictions, the overburden pressure is below the minimum required pressure, however the calculated fracture pressure is above the maximum pressure. Frac-out risk can be reduced by maintaining the drilling fluid pressure around the minimum required calculated drilling fluid pressures, by keeping a clean borehole, using appropriate drilling fluid properties, allowing adequate circulation time and volume to remove cuttings, and making wiper trips to mechanically clean the borehole. Careful monitoring of fluid volume in the system and returns back to rig, as well as active formation management with drilling fluid additives are 00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 23 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. important to the success of an HDD installation. It is recommended that the fluid pressure be controlled at all times and be maintained at minimum levels required for drilling. NOISE AND TRAFFIC CONTROL Due to the residents/cottages on the entry side, it is recommended to carry out assessment/study on the potential noise affect caused by the HDD construction, especially during casing installation process. Traffic control during construction shall also be implemented through residential areas.

9 OTHER RISKS AND MITIGATION MEASURES

Risk Category Description Unmitigated Mitigation Strategy Mitigated Risk Level Risk Level

Geotechnical Changing formations may Medium To have mud technician on site Low negatively effect drilling to continuous monitor all fluid properties such as drilling fluid properties and mud density, viscosity, awareness of where the sand content, PH and formation zones are changing. salinities . Casing 72" 50m entry casing may High Telescoping casing can be Medium Installation not be able to reach the used. designed casing depth. Refer to section 8.2 for more information. Casing Entry casing may not be High Casing angle can be monitored Medium Installation installed straight along the during installation with drill alignment as designed inclinometer due to length and size of the casing required. After casing is installed, position shall be confirmed by accurate steering survey outside of the casing. If any deviation, HDD design shall be updated to match the surveyed casing alignment.

Uninstallation Difficulties may be High Use of sufficiently size Hammer Medium of Casing encountered removing the and compressor for removing casing after completion of the casing.

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 24 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. the drill. If the casing Provide quality control checks cannot be removed, this to ensure Casing will come out. could cause a cathodic protection issue. Drill Rigs and For this project, the Medium Prior to commencement of the Low Equipment proposed Entry Rig is construction, Rigs availability Availability 880,000lbs and Exit rig is for this crossing shall be 440,000lbs. The availability confirmed. of the rigs may be limited due to multiple large size rigs required for the scope of the project.

10 CROSSING CONTINGENCY

The primary method of construction to cross the Mcleod River is by horizontal directional drill. This is about 1,051m HDD proposed within this design report. Although horizontal directional drilling is often considered as a current industry standard for water crossings however, in the event that the drill is unsuccessful an open-cut shall be considered as contingency.

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 25 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd. 11 CONCLUSION

Based on the information available, detailed calculation and design, it is considered that an HDD installation at the Mcleod River crossing location is technically feasible. However, the challenge to install the 50m casing will make this HDD crossing a high risk. Potential risks associated with HDD construction have been discussed herein. Prior to construction, buoyancy control plan, drill string management plan, engineered drilling fluid plan, fluid release containment procedures and drilling waste disposal plan shall be developed based on site specific conditions. Regulatory requirements shall be on site and reviewed prior to construction. If the crossing is impacting special areas such as endangered plant and/or species, appropriate measures shall be taken and sensitive habitat requirements shall be followed to reduce or minimize the impacts. Government guidelines such as transportation, local road weight restrictions, noise bylaws, and lighting restrictions shall be followed. An independent assessment of the construction of the Mcleod River HDD crossing is also recommended to be conducted by the drilling contractor with consideration of the followings at least, but not limited to: • Final Issued for Construction (IFC) design drawing; • Suitable attention to the site specific sub-surficial and engineering issues discussed; • Proper construction planning, schedules and procedures; • Execution of good workmanship during construction.

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 26 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd.

For and on behalf of TerraHDD Solutions Inc.

APEGA PERMIT TO PRACTICE # P12265

Originated by:

Peter Liang, P.Eng Parth Patel, E.I.T Mechanical Engineer Mechanical Engineer

Reviewed & Approved by:

Brett Ribaric Scott Gilles Construction Manager President

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 27 of 29

2021 NGTL System Expansion Project

Nova Gas Transmission Ltd.

Appendix 1

HDD DESIGN DRAWING

00796-THD-C-RP-0013_2020-09-09 HDD Feasibility Report - Mcleod River Crossing

Page 28 of 29

Ø Ø Ø

· · ·

· · ·