NOVA Gas Transmission Ltd. NGTL West Path Delivery 2022 Attachment 6 Desktop Geohazards Preliminary Assessment Raven River Section ABC Section NOVA Gas Transmission Ltd. Attachment 6 NGTL West Path Delivery 2022 Desktop Geohazards Preliminary Assessment REPORT Phase I Geologic Hazards Assessment for the Edson Mainline Loop No. 4 Raven River Section, Alberta, Canada Submitted to: NOVA Gas Transmission Ltd. 450 1 Street SW Calgary, AB T2P 5H1 Submitted by: Golder Associates Ltd. 2800, 700 - 2nd Street S.W., Calgary, Alberta, T2P 2W2, Canada +1 403 299 5600 01189-GAL-C-RP-0002_1 May 26, 2020 June 2020 Page 1 of 132 NOVA Gas Transmission Ltd. Attachment 6 NGTL West Path Delivery 2022 Desktop Geohazards Preliminary Assessment Table of Contents 1.0 INTRODUCTION AND PROJECT LOCATION .............................................................................................. 1 1.1 Purpose and Scope .............................................................................................................................. 1 1.2 Phase I Assessment Summary ............................................................................................................ 2 1.3 Report Structure ................................................................................................................................... 3 2.0 PHYSIOGRAPHY AND GEOLOGIC SETTING ............................................................................................. 3 3.0 METHODOLOGY ............................................................................................................................................ 3 3.1 General ................................................................................................................................................. 3 3.2 Development of Hazard Identification and Classification Criteria ........................................................ 4 3.2.1 Landslides ....................................................................................................................................... 4 3.2.2 Seismic (Ground Shaking) .............................................................................................................. 6 3.2.3 Seismic (Liquefaction) ..................................................................................................................... 6 3.2.4 Seismic (Surface Fault Rupture) ..................................................................................................... 8 3.2.5 Subsidence (Karst) ......................................................................................................................... 8 3.2.6 Subsidence (Underground Mining) ................................................................................................. 8 3.2.7 Subsidence (Fluid Withdrawal) ....................................................................................................... 9 3.2.8 Collapsible or Expansive Soils ...................................................................................................... 10 4.0 RESULTS ...................................................................................................................................................... 11 4.1 Landslide Hazards ............................................................................................................................. 12 4.2 Seismic Hazards ................................................................................................................................ 12 4.3 Subsidence Hazards .......................................................................................................................... 13 4.3.1 Karst .............................................................................................................................................. 13 4.3.2 Underground Mines ...................................................................................................................... 14 4.3.3 Fluid Withdrawal............................................................................................................................ 14 4.4 Collapsible or Expansive Soils ........................................................................................................... 14 5.0 RECOMMENDATIONS ................................................................................................................................. 15 5.1 All Hazards ......................................................................................................................................... 15 June 2020 Page 2 of 132 NOVA Gas Transmission Ltd. Attachment 6 NGTL West Path Delivery 2022 Desktop Geohazards Preliminary Assessment 5.2 Landslide Hazards ............................................................................................................................. 15 5.3 Seismic Hazards ................................................................................................................................ 15 5.4 Subsidence Hazards .......................................................................................................................... 16 5.5 Collapsible or Expansive Soils ........................................................................................................... 16 6.0 CLOSURE ..................................................................................................................................................... 17 7.0 REFERENCES .............................................................................................................................................. 18 7.1 Alphabetical References .................................................................................................................... 18 7.2 References by Hazard Type .............................................................................................................. 23 TABLES Table 1 – Edson Mainline Loop No. 4 Raven River Section - Phase I Geologic Hazards Classification Summary Table 2 – Edson Mainline Loop No. 4 Raven River Section - System Phase I Summary of Hazards FIGURES Figure 1 – Edson Mainline Loop No. 4 Raven River Section - Overview Map Figure 2 – Edson Mainline Loop No. 4 Raven River Section - Landslide Hazard Areas Figure 3 – Edson Mainline Loop No. 4 Raven River Section - Seismic Hazard Areas (Ground Shaking and Liquefaction) Figure 4 – Edson Mainline Loop No. 4 Raven River Section - Fluid Withdrawal Subsidence Hazard Areas Figure 5 – Edson Mainline Loop No. 4 Raven River Section - Expansive and Collapsible Soils Hazard Areas APPENDICES Appendix A – Electronic Files June 2020 Page 3 of 132 NOVA Gas Transmission Ltd. Attachment 6 NGTL West Path Delivery 2022 Desktop Geohazards Preliminary Assessment 1.0 INTRODUCTION AND PROJECT LOCATION This report is a summary of the results of a desktop Phase I Geologic Hazards Assessment (Phase I Assessment) conducted by Golder Associates Ltd. (Golder) for the NOVA Gas Transmission Ltd. (NGTL), a wholly owned subsidiary of TransCanada PipeLines Limited (TCPL), an affiliate of TC Energy Corporation, proposed Edson Mainline Loop No. 4 Raven River Section (Project), in Alberta, Canada. We completed this Phase I Assessment in support of the engineering, design and construction of the Project. The proposed pipeline section assessed herein is the approximately 18 kilometres (km) long NPS 48 Edson Mainline Loop No. 4 Raven River Section that will extend from the Schrader Creek East Compressor Station in the south (KP 0+000) to the Clearwater Compressor Station in the north (KP 18+212 in the north), as shown on Figure 1. 1.1 Purpose and Scope The purpose of this Phase I Assessment was to complete a regional-scale identification and assessment of potential geologic hazards that may affect the Project. The geologic hazards assessment is intended to be used by NGTL for development of an inventory of potential geologic hazards that could affect the Project during and after construction, which, in turn, can be used for planning risk management of the system. Additionally, this Phase I Assessment is intended to be used for identification of areas for possible additional investigation to more fully characterize and mitigate geologic hazards in subsequent phases of hazard assessment. Golder has completed Phase I Assessments in the recent past for the NGTL pipeline system (Golder 2015a, 2016a, 2017, 2018a and 2018b). Because portions of this Project are located adjacent to work previously performed by Golder, we reviewed and incorporated relevant results into this Project. To carry out the Phase I Assessment, we compiled, reviewed, and analyzed regional-scale maps and reports from public sources, and conducted a remote sensing review of available LiDAR data and aerial imagery. We conducted our assessment along the proposed alignment KMZ files provided by NGTL on February 2, 2020. The proposed pipeline will primarily parallel the existing NGTL Pipelines, which have been previously assessed by Golder (Golder 2015a, 2016a). No aerial reconnaissance was completed by Golder during this assessment, however a helicopter reconnaissance was completed as part of the 2015 assessment of nearby pipelines. Relevant findings from the 2015 helicopter reconnaissance are included in landslide descriptions in Section 4.1 of this report. For the purposes of the Phase I Assessment and this report, a geologic hazard is a natural geologic condition, ongoing geologic process, or potential natural event that could adversely affect the construction,