5107-5119 Main St & 196 E 35Th Preliminary Hydrogeological Report
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220 - 18 Gostick Place P: 604-990-0546 North Vancouver, BC F: 604-990-0583 Canada V7M 3G3 www.horizoneng.ca PRELIMINARY HYDROGEOLOGICAL STUDY Proposed Multi-Family Development 5107-5119 Main Street & 196 East 35th Avenue Vancouver, BC Our File: 120-4724 August 10, 2020 Consulting Geotechnical Engineers ©Horizon Engineering Inc. Proposed Multi-Family Development Our File: 120-4724 5107-5119 Main Street & 196 East 35th Avenue, Vancouver, BC August 10, 2020 Preliminary Hydrogeological Study Page ii TABLE OF CONTENTS 1.0 INTRODUCTION ............................................................................................................. 1 2.0 SITE INFORMATION ...................................................................................................... 1 2.1 Referenced Documents ............................................................................................... 1 2.2 Site Description ............................................................................................................ 1 2.3 Existing Buildings ......................................................................................................... 2 2.4 Site Grades .................................................................................................................. 2 2.5 Proposed Development ............................................................................................... 2 3.0 BACKGROUND INFORMATION .................................................................................... 3 3.1 Surficial Geology .......................................................................................................... 3 3.2 Groundwater Records .................................................................................................. 5 3.2.1 Quadra Sands Aquifer .......................................................................................... 5 3.2.2 Well Records Search ............................................................................................ 6 3.3 Existing Boreholes ....................................................................................................... 9 3.4 Existing Watercourses ................................................................................................. 9 4.0 SUBSURFACE INVESTIGATION ................................................................................... 9 4.1 Soil Conditions ............................................................................................................10 4.1.1 Fill / Topsoil .........................................................................................................10 4.1.2 Organic Silt ..........................................................................................................10 4.1.3 Sand to Silt / Sandy Silt to Silty Sand ...................................................................10 4.1.4 Sand (till-like) .......................................................................................................10 4.2 Groundwater Conditions .............................................................................................10 4.3 Proposed Supplementary Investigation and Field Works ............................................10 4.3.1 Supplementary Field and Lab Works ...................................................................11 5.0 GROUNDWATER MANAGEMENT PLAN .....................................................................11 5.1 Foundation Type .........................................................................................................11 5.2 Temporary Dewatering (During Construction) .............................................................12 5.3 Long-Term Dewatering (Following Construction) ........................................................12 6.0 IMPACT ASSESSMENT ................................................................................................12 6.1.1 Lowered Water Levels and Ground Subsidence ..................................................12 6.1.2 Environmental ......................................................................................................13 6.1.3 Water Quality, Fish, Wildlife, Ecosystems ............................................................13 6.1.4 Artesian ...............................................................................................................13 6.1.5 Flooding ...............................................................................................................13 6.1.6 Erosion ................................................................................................................14 6.2 Avoidance / Mitigation Measures ................................................................................14 7.0 REVIEW .........................................................................................................................14 8.0 CLOSURE ......................................................................................................................15 Consulting Geotechnical Engineers ©Horizon Engineering Inc. Proposed Multi-Family Development Our File: 120-4724 5107-5119 Main Street & 196 East 35th Avenue, Vancouver, BC August 10, 2020 Preliminary Hydrogeological Study Page iii LIST OF TABLES Table 1: Flowing Artesian Groundwater Wells Records (generally listed from west to east) ....... 6 Table 2: Well Records Near Subject Site ................................................................................... 7 Table 3: Oakridge Mall Well Records Summary ......................................................................... 7 Table 4: Oakridge Mall Planned Temporary Dewatering Wells ................................................... 8 Table 5: Langara Golf Course Well Records Summary .............................................................. 8 LIST OF FIGURES Figure I: Plan location of subject site (red circle) showing surficial geology and proximity to Section B-B’. ........................................................................................................................................... 3 Figure II: Plan location of subject site (red circle) showing 'Groundwater Areas of Concern'. ..... 4 Figure III: Partial Section B-B’ from Geological Survey of Canada Map 1486A. ......................... 5 APPENDICES Appendix A: Figures > Figure 1: Site Location Plan > Figure 2: Test Hole Location Plan Appendix B: Test Hole Logs Appendix C: Submission Checklist for Hydrogeological Studies Consulting Geotechnical Engineers ©Horizon Engineering Inc. Proposed Multi-Family Development Our File: 120-4724 5107-5119 Main Street & 196 East 35th Avenue, Vancouver, BC August 10, 2020 Preliminary Hydrogeological Study Page 1 1.0 INTRODUCTION This document reports on the results of the preliminary hydrogeological study carried out for the subject site and is intended to support the Re-Zoning Application for the proposed development. This report has been prepared in general conformance with our emailed supplementary scope of services dated May 22, 2020. This document has been developed to satisfy the requirements of the City of Vancouver Groundwater Management Bulletin (amended April 20, 2020) Section 2.3.2 and Appendix A. The subject site is within the Cambie Corridor Sewershed 'groundwater area of concern'. 2.0 SITE INFORMATION 2.1 Referenced Documents We have been provided with the following documents for the subject site: • Pre-Application Drawings prepared by Integra Architecture Inc., dated September 24, 2018, and • Little Mountain Adjacent Area Rezoning Policy for the City of Vancouver. We have also referred to the following, publicly accessible sources to collect additional information in the vicinity of the subject site: • City of Vancouver Online Geographic Information Systems (GIS), • Geologic Survey of Canada Map 1486A, • Vancouver’s Old Streams Map, • Province of British Columbia well records and aquifer summaries described herein, and • others, as available and noted in this report. 2.2 Site Description The subject site is located in the “Little Mountain Adjacent Area” of the City of Vancouver and comprises three, single-family residential lots with civic addresses 5107 and 5119 Main Street and 196 East 35th Avenue in Vancouver, BC. The overall property is approximately rectangular in shape with overall dimensions of approximately 33 metres (110 feet) in the east-west direction by 30 metres (100 feet) in the north-south direction. As shown in Figure 1 attached to this report, the site is bounded by East 35th Avenue to the north, Main Street to the east, the proposed 'Little Mountain' development site (by others) to the south, and a paved lane (indicated to be approximately 6 metres wide) in turn bounded by an existing 6- storey building with a below-grade parkade to the west. The site area is understood to encompass a footprint of approximately 1,011 square meters (10,886 square feet). The site is adjacent to the proposed 'Little Mountain' site, a social housing redevelopment site by BC Housing. It is understood that the area of the 'Little Mountain' site at the south of the subject site will be developed with multi-family building with two levels of below-grade parking. At the south side of the property, an at-grade pedestrian thoroughfare is proposed; it is understood that this will be located half on the subject property and half on the neighbouring redeveloped 'Little Mountain' site (for a total pathway width of 3.0 metres). Consulting Geotechnical Engineers ©Horizon Engineering Inc. Proposed