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The Vancouver landfill : final closure strategy Foisy, Janine Jennifer 2000

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The Vancouver Landfill - Final Closure Strategy By JANINE JENNIFER FOISY B.Sc, The University of British Columbia, 1995  A THESIS SUBMITTED IN P A R T I A L F U L F U L M E N T OF THE REQUIREMENTS FOR THE D E G R E E OF M A S T E R OF APPLIED SCIENCE in  THE F A C U L T Y OF G R A D U A T E STUDIES (Department of Civil Engineering; School of Environmental Engineering; Pollution Control and Waste Management) We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH C O L U M B I A July 2000 © Janine Jennifer Foisy, 2000  In  presenting  degree freely  at  the  available  copying  of  department publication  this  of  in  partial  fulfilment  University  of  British  Columbia,  for  this or  thesis  reference  thesis by  this  for  his  and  scholarly  or  thesis  study.  her  for  of  £t\ji  j  purposes  gain  0  The University of British Columbia Vancouver, Canada  DE-6  (2/88)  o  the  shall  requirements  agree  that  agree  may  representatives.  financial  -g>y  I  I further  permission.  Department  of  be  It not  is be  that  the  for  Library  an shall  permission for  granted  by  understood allowed  advanced  the that  without  make  it  extensive  head  of  copying my  my or  written  Abstract The body of work presented in this Thesis document provides a comprehensive examination of final cover design for municipal solid waste landfills. Accompanying general design principals is the investigation and resulting recommendations for issues specific to the closure of the Vancouver Landfill. The first objective of the Thesis was to develop a set of physical characteristics for soil materials, which would allow for the construction of a lowpermeability barrier layer meeting British Columbia guidelines. The second objective was to then use the developed soil criteria to evaluate the suitability of Lower Mainland soils. The physical characteristic of soil material, originating from trench excavations in Vancouver, was closely examined and the material evaluated for use in all layers of final cover design. The last objective of the Thesis was to investigate the use of alternative cover materials, including geosynthetics, in final cover design. The combination of a comprehensive literature review and the implementation of a program of soil sample collection and analysis allowed for the completion of the above objectives. Testing of soil samples included the determination of the grain size distribution to the clay fraction level. The major findings of the work are that soil sources in the City of Vancouver are not suitable for use in the construction of a low-permeability barrier layer. Suitable soil sources however, can be found in areas of Surrey and Langley. Trench excavation soil is recommended for use in the foundation layer of the final cover. Lastly, geosynthetic materials are a viable alternative to the use of soil in final cover design. A polyvinyl chloride (PVC) geomembrane would be the most suitable geosynthetic based barrier layer for the requirements of the Vancouver Landfill.  The Vancouver Landfill  ii  Final Closure Strategy  Table of Contents Abstract  ii  List o f Tables  vi  List o f Figures  viii  1 INTRODUCTION  1  2 OBJECTIVES  4  3 RESEARCH METHODS  5  4 FINAL C L O S U R E DESIGN AND D E V E L O P M E N TO F SOIL SELECTION CRITERIA  9  4.1 INTRODUCTION  9  4.2 OVERVIEW OF REGULATIONS  9  4.3 CLOSURE DESIGN AND COST ANALYSIS - SPERLING HANSEN ASSOCIATES  10  4.4 APPROACH TO DESIGN OF FINAL COVER  15  4.4.1 Surface Layer (Vegetative) 4.4.2 Drainage Layer 4.4.3 Barrier Layer 4.4.3.1 Moisture Content and Compactive Energy 4.4.3.2 Dessication Cracking 4.4.3.3 Slope-Stability 4.4.3.4 Differential Settlement 4.4.4 Gas Collection Layer 4.4.5 Foundation Layer 4.4.6 Summary  17 19 19 24 27 28 30 34 35 35  4.5 HYDRAULIC CONDUCTIVITY LABORATORY TESTING  35  4.5.1 Background 4.5.2 Testing Methods 4.5.3 Results  35 38 38  4.6 SUMMARY  39  5 SOIL MAPPING  41  5.1 INTRODUCTION  41  5.2 LITERATURE REVIEW  42  5.2.1 Regional Setting 5.2.2 Climate 5.2.3 Regional Geology 5.2.3.1 Bedrock Geology 5.2.3.2 Quaternary (Surficial Geology) 5.2.4 Classification and Composition of Deposits 5.2.4.1 Waterlain Sediments 5.2.4.2 Glacier Ice Sediments 5.2.4.3 Glaciomarine and Glaciolacustrine Sediments 5.2.4.4 Colluvial Sediments 5.2.4.5 Lowland Deposits 5.2.5 Surficial Geology Maps 5.2.6 Soils Report - H. A. Luttmerding 5.2.7 Ocean Disposal Data 5.2.1.\ Broadway Corridor (West) 5.2.7.2 Broadway Corridor (East) 5.2.7.3 Vancouver-Other  The Vancouver Landfill  iii  42 43 44 44 44 44 45 45 46 47 47 48 53 75 78 80 82  Final Closure Strategy  5.2.7.4 Downtown 5.2.7.5 Discusssion/Conclusion  83 90  5.2.8 Geotechnical Records  92  5.3 S A M P L E C O L L E C T I O N A N D A N A L Y S I S  97  5.3.1 Literature Review - Laboratory Testing Procedures  97  5.3.1.1 Grain Size Analysis  98  5.3.2 Materials and Methods  104  5.3.2.1 Sample Collection 5.3.2.2 Grain Size Analysis 5.3.2.3 SediGraph and Organic Content Determinations  104 104 106  5.3.3 Results  107  5.3.3.1 Trench Excavation Data 5.3.3.1.1 15th and Trimble (Label Number 1, Map 1) 5.3.3.1.2 12th and Discovery (Label Number 2, Map 1) 5.3.3.1.3 10th and Camosun (Label Number 3, Map 1) 5.3.3.1.4 Granville and 4 (Label Number 4, Map 2) 5.3.3.1.5 19th and Arbutus (Label Number 5, Map 2) 5.3.3.1.6 Lane West 26th and Oak (Label Number 6, Map 2) 5.3.3.1.7 Angus and Laburnum (Label Number 7, Map 3) 5.3.3.1.8 70th and Heather (Label Number 8, Map 3) 5.3.3.1.9 57th and Pr. Edward (Label Number 9, Map 4) 5.3.3.1.10 46th and Quebec (Label Number 10, Map4) 5.3.3.1.11 1500 East 57 (Label Number 11, Map 5) 5.3.3.1.12 47th and Commercial (Label Number 12, Map5) 5.3.3.1.13 Harold and Marmion (Label Number 13, Map 6) 5.3.3.1.14 38th and Fraser (Label Number 14, Map 7) 5.3.3.1.15 30th and Windsor (Label Number 15, Map 7) 5.3.3.1.16 Miller and Kingsway (Label Number 16, Map 7) 5.3.3.1.17 18th and Fraser (Label Number 17, Map 7) 5.3.3.1.18 4th and Victoria/Commercial (Label Number 18,Map8) 5.3.3.1.19 New Brighton Park (Label Number 19, Map 9) 5.3.3.2 Large-Scale Excavation Projects 5.3.3.2.1 Broadway and Alma (Label Number 1, Map 1) 5.3.3.2.2 Burrard and 4 (Label Number 2, Map 2) 5.3.3.2.3 Broadway and Pine (Label Number 3, Map 2) 5.3.3.2.4 56 East 2nd Ave. (Label Number 4, Map 2) 5.3.3.2.5 Hornby and Helmcken (Label Number 5, Map 10) 5.3.3.2.6 1239 West Georgia (Label Number 6, Map 10) 5.3.3.2.7 McKay and Kingsway (Label Number 7, Surficial Geology Vancouver (1486A)) 5.3.3.3 Discussion th  th  th  5.3.4 Conclusion  111 112 112 113 113 114 115 115 117 118 118 119 120 120 121 121 122 123 124 124 125 126 129 131 134 135 136 137 138  141  6 ALTERNATIVE COVER MATERIALS  144  6.1 I N T R O D U C T I O N  144  6.2 F R A S E R R I V E R D R E D G I N G O P E R A T I O N S  144  6.3 G E O S Y N T H E T I C S  146  6.3.1 Introduction 6.3.2 Geosynthetics - General Properties  146 148  6.3.2.1 Polymer Types 6.3.2.1.1 Overview 6.3.2.1.2 Polymer Formulations 6.3.2.2 Manufacturing Processes 6.3.2.2.1 Geotextiles 6.3.2.2.2 Geomembranes 6.3.2.2.3 Geosynthetic Clay Liners 6.3.2.3 Degradation Processes 6.3.2.3.1 Ultraviolet Radiation 6.3.2.3.2 Oxidation 6.3.2.3.3 Hydrolysis 6.3.2.3.4 Chemical 6.3.2.3.5 Radiation  148 148 150 151 151 152 153 154 154 154 156 156 157  The Vancouver Landfill  iv  Final Closure Strategy  6.3.2.3.6 Biological 6.3.2.3.7 Temperature (Thermal Effects) 6.3.3 Design 6.3.3.1 Design Methods 6.3.3.2 Geotextiles 6.3.3.2.1 Overview 6.3.3.2.2 Filtration 6.3.3.2.3 Gas Collection 6.3.3.2.4 Survivability Requirements 6.3.3.3 Geomembranes 6.3.3.3.1 Barrier Design 6.3.3.3.2 Survivability Requirements 6.3.3.4 Geosynthetic Clay Liners 6.3.3.4.1 Barrier Design 6.3.3.4.2 Survivability Requirements 6.3.3.5 Slope Design 6.3.3.6 Quality Assurance/Quality Control 6.3.4 Conclusion  157 157 158 158 158 158 158 160 160 161 161 163 164 164 164 165 169 169  7 DISCUSSION  171  7.1 DEVELOPMENT OF BARRIER SELECTION CRITERIA AND TESTING PROCEDURES  171  7.2 EVALUATION OF CITY OF VANCOUVER SOIL SOURCES  177  7.3 ALTERNATIVE SOIL SOURCES AND GEOSYNTHETICS  183  7.4 SUMMARY  187  8 CONCLUSIONS  188  9 REFLECTIONSAND ACKNOWLEDGEMENTS  190  10 R E F E R E N C E S  192  APPENDIX A - O C E A N DISPOSAL C L A Y R E Q U I R E M E N T DETERMINATION  197  APPENDIX B - G E O T E C H N I C A L INVESTIGATION - SOILS R E P O R T  199  APPENDIX C - TECHNICAL GUIDANCE - MICROMERICTICS  203  APPENDIX D - O C E A N DISPOSAL - R A W D A T A  205  APPENDIX E - VISUAL T R E N C H SOILS R E P O R T S - CITY O F V A N C O U V E R  226  APPENDIX F - T R E N C H EXCAVATIONS - R A W DATA  242  APPENDIX G - LARGE-SCALE EXCAVATIONS - R A W D A T A  439  APPENDIX H - FRASER RIVER DREDGE - R A W D A T A  574  A P P E N D I X I - G I S G E N E R A T E D M A P S H E E T S 1-10  598  The Vancouver Landfill  v  Final Closure Strategy  List of Tables Table 1: Final Cover Material Requirements Table 2: Final Closure Unit Costs - Option I: Low Permeability Soil Barrier Table 3: Final Closure Unit Costs - Option 2: PVC Geomembrane Cover System Table 4: Final Closure Unit Costs - Option 3: PVC/Clay Composite Cover System Table 5: Final Closure Unit Costs - Option 4: MoELP Type Soil Barrier Table 6: Estimated Final Closure Costs Table 7: Recommended Tree Species for Use at Landfill Sites Table 8: Summary of Literature Recommended Soil Selection Criteria Table 9: Compilation of Published Tensile Strains at Failure for Cover Materials Table 10: Hydraulic Conductivity of Earth Materials Table 11: Hydraulic Conductivity Results Table 12: Relationship Between Classified Soils and Surficial Deposits - Surrey and Langley Table 13: Reported Data for Soils Identified as Abbotsford (1976) Table 14: Reported Data for Soils Identified as Abbotsford (1972) Table 15: Reported Data for Soils Identified as Albion (1970) Table 16: Reported Data for Soils Identified as Albion (1972-1) Table 17: Reported Data for Soils Identified as Albion (1972-2) Table 18: Reported Data for Soils Identified as Berry Table 19: Reported Data for Soils Identified as Bose (1960) Table 20: Reported Data for Soils Identified as Bose (1972) Table 21: Reported Data for Soils Identified as Cloverdale (1965) Table 22: Reported Data for Soils Identified as Cloverdale (1972-1) Table 23: Reported Data for Soils Identified as Cloverdale (1972-2) Table 24: Reported Data for Soils Identified as Columbia (1967) Table 25: Reported Data for Soils Identified as Columbia (1972) Table 26: Reported Data for Soils Identified as Fairfield Table 27: Reported Data for Soils Identified as Ladner (1972-1) Table 28: Reported Data for Soils Identified as Ladner (1972-2) Table 29: Reported Data for Soils Identified as Langley (1965) Table 30: Reported Data for Soils Identified as Langley (1972) Table 31: Reported Data for Soils Identified as Livingstone (1965) Table 32: Reported Data for Soils Identified as Livingstone (1972) Table 33: Reported Data for Soils Identified as Matsqui (1972) Table 34: Reported Data for Soils Identified as Milner (1972) Table 35: Reported Data for Soils Identified as Monroe (1972) Table 36: Reported Data for Soils Identified as Nicholson (1970) Table 37: Reported Data for Soils Identified as Nicholson (1972) Table 38: Reported Data for Soils Identified as Page (1967) Table 39: Reported Data for Soils Identified as Page (1972) Table 40: Reported Data for Soils Identified as Richmond Table 41: Reported Data for Soils Identified as Spetifore (1968) Table 42: Reported Data for Soils Identified as Spetifore (1972) Table 43: Reported Data for Soils Identified as Scat Table 44: Reported Data for Soils Identified as Summer Table 45: Reported Data for Soils Identified as Sunshine Table 46: Reported Data for Soils Identified as Vinod. Table 47: Reported Data for Soils Identified as Whatcom (1965) Table 48: Reported Data for Soils Identified as Whatcom (1972-1) Table 49: Reported Data for Soils Identified as Whatcom (1972-2) Table 50: Description of Remaining Identified Soils - Surrey and Langley Table 51: Point Grey Excavation Disposal Volumes Table 52: Ocean Disposal Data - Broadway Corridor (West)  The Vancouver Landfill  vi  Final Closure Strategy  12 13 14 14 14 /5 19 24 31 36 39 54 55 55 56 56 56 57 58 58 59 59 59 60 60 61 61 62 62 63 63 64 64 65 65 66 66 67 67 68 69 69 69 70 70 71 72 72 72 74 77 79  Table 53: Ocean Disposal Data - Broadway Corridor (East) 81 Table 54: Ocean Disposal Data - Vancouver (Other) 82 Table 55: Ocean Disposal Data - Downtown (Seymour-Cambie, Nelson-Georgia) 83 Table 56: Ocean Disposal Data - Downtown (Seymour St., Pacific St., Helmcken St.) 84 Table 57: Ocean Disposal Data - Downtown (Georgia andDenman) 85 Table 58: Ocean Disposal Data - Downtown (Burrard, Water, Dunsmuir) 86 Table 59: Ocean Disposal Data - Downtown (Burrard and Nelson) 87 Table 60: Ocean Disposal Data - Downtown (Melville St., Broungton St., Robson St., Thurlow St.) 88 Table 61: Ocean Disposal Data - Downtown (Burrard St., Helmcken St., Granville St., Pacific St.) 89 Table 62: Ocean Disposal Data - Downtown (Other) 90 Table 63: Soil Classification (Unified Soil Classification System) 94 Table 64: SediGraph Data: 38 and Fraser 109 Table 65: Location Information and Associated Label Number and Map Sheet Number - Trench and Largescale Excavation Projects /// Table 66: Laboratory Testing Results for Soil Samples Collected at 15 and Trimble /12 Table 67: Laboratory Testing Results for Soil Samples Collected at 12 and Discovery 113 Table 68: Laboratory Testing Results for Soil Samples Collected at 10 and Camosun 113 Table 69: Laboratory Testing Results for Soil Samples Collected in the Area of Granville and 4 114 Table 70: Laboratory Testing Results for Soil Samples Collected at 19 and Arbutus /15 Table 71: Laboratory Testing Results for Soil Samples Collected at 26 and Oak /15 Table 72: Laboratory Testing Results for Soil Samples Collected at Angus and Laburnum 117 Table 73: Laboratory Testing Results for Soil Samples Collected at 70* and Heather /18 Table 74: Laboratory Testing Results for Soil Samples Collected at 57 and Pr. Edward. 118 Table 75: Laboratory Testing Results for Soil Samples Collected at 46 and Quebec 119 Table 76: Laboratory Testing Results for Soil Samples Collected at 1500 East 57 120 Table 77: Laboratory Testing Results for Soil Samples Collected at 47 and Commercial. 120 Table 78: Laboratory Testing Results for Soil Samples Collected at Harold and Marmion 121 Table 79: Laboratory Testing Results for Soil Samples Collected at 38 and Fraser 121 Table 80: Laboratory Testing Results for Soil Samples Collected in the Area of 30 and Windsor 122 Table 81: Laboratory Testing Results for Soil Samples Collected at Miller and Kingsway 122 Table 82: Laboratory Testing Results for Soil Samples Collected at 18 and Fraser 123 Table 83: Laboratory Testing Results for Soil Samples Collected at 4 and Victoria/Commercial. 124 Table 84: Laboratory Testing Results for Soil Samples Collected at New Brighton Park 125 Table 85: Laboratory Testing Results for Soil Samples Collected at Broadway and Alma 126 Table 86: Laboratory Testing Results for Soil Samples Collected at Burrard and 4' 130 Table 87: Laboratory Testing Results for Soil Samples Collected at Broadway and Pine 134 Table 88: Laboratory Testing Results for Soil Samples Collected at 56 East 2 Ave 135 Table 89: Laboratory Testing Results for Soil Samples Collected at Hornby and Helmcken 136 Table 90: Laboratory Testing Results for Soil Samples Collected at 1239 West Georgia 137 Table 91: Laboratory Testing Results for Soil Samples Collected at McKay and Kingsway (Burnaby) 137 Table 92: Grain Size Distribution Results of Fraser River Dredge Material - Fraser Surrey Docks 145 Table 93: Grain Size Distribution Results of Fraser Dredge Material - Ecowaste 145 Table 94: Common Repeating Units and Geosynthetic Types 149 Table 95: Generalized Polymer Formulations / 51 Table 96: Geotextile Strength Properties 161 Table 97: Recommended Minimum Properties-Geomembrane Installation 163 Table 98: Peak Friction Values 166 Table 99: Summary of GCL (Internal) Direct Shear Test Results 167 Table 100: Recommended Global Factor of Safety Values in Performing Stability Analysis of Final Cover Systems 168 Table 101: Recommended Selection Criteria and Laboratory Test Methods for the Evaluation of Hydraulic Barrier Soil Materials 174 th  lh  th  lh  th  th  lh  th  th  lh  th  ,h  th  th  ,h  h  nd  The Vancouver Landfill  vn  Final Closure Strategy  List of Figures Figure 1: Vancouver Landfill Final Contour Schematic 11 Figure 2: Generalized Final Cover 17 Figure 3: Basic Building Blocks of Clay Minerals 21 Figure 4: Effect of Molding Water Content Upon (a) Dry Unit Weight; and (b) Hydraulic Conductivity 24 Figure 5: Highly Plastic Soil Compacted with Standard Proctor Effort at Water Content of (a) 16% (1% Dry of Optimum) and (b) 20% (3% Wet of Optimum) 25 Figure 6: Relationship Between Tensile Strain and Distortion ( A/L) 32 Figure 7: Map of Fraser Lowland 42 Figure 8: Surficial Geology Map of Vancouver (Map 1486A) Oversized Figure 9: Surficial Geology Map of New Westminster (Map 1484A) Oversized Figure 10: Luttmer ding Map Sheet Oversized Figure 11: Ocean Disposal Sites in Southern British Columbia 76 Figure 12: Plasticity Chart 92 Figure 13: SediGraph Data: 38 and Fraser 109 Figure 14: Photo - Trench Excavation - Angus and Laburnum 116 Figure 15: Photo - Angus and Laburnum-Sand/Clay Separation 116 Figure 16: Photo - Broadway and Alma 127 Figure 17: Photo - Broadway and Alma - Compressed Sandstone 128 Figure 18: Photo - Broadway and Alma - Site Crushed Sandstone 129 Figure 19: Photo - Burrard and 4 - Layered Siltstone and Claystone 130 Figure 20: Photo - Broadway and Pine 132 Figure 21: Photo - Broadway and Pine - Glacial Till 133 Figure 22: Photo - 1239 W Georgia 136 Figure 23: Summary Plot of Trench Excavation Soil Grain Size Characteristics 140 Figure 24: Types of Polymeric Fibers Used in the Manufacture of Geotextiles 152 Figure 25: Oxidation Stages 155 Figure 26: Three Dimensional Axi-symmetric Stress vs Strain Response Curves for Types of Various Geomembranes 162 th  ,h  The Vancouver Landfill  viii  Final Closure Strategy  1  I N T R O D U C T I O N  The following document provides a comprehensive examination of final cover design for municipal solid waste landfills, including general design principals and issues specific to the Vancouver Landfill. A general discussion of final cover design is followed by the development of soil selection criteria to evaluate source material for construction of a hydraulic barrier layer. A large portion of the Thesis is a soil investigation component, where the geologic history and surficial geology of the Lower Mainland region is explored. Soil sources are evaluated for suitability as hydraulic barrier layer construction material based on literature data and laboratory testing of collected samples. A final component of the Thesis is an investigation in the use of alternative materials, including geosynthetics, in landfill final cover design. A n integral component of solid waste management in British Columbia is the deposition of waste materials into an engineered landfill. The Vancouver Landfill is situated in the Municipality of Delta, just south of the George Massey Tunnel on the north side of Hwy. 99. The facility has been developed on the southern edge of Burns Bog. Landfilling operations have been ongoing since 1966 and a recent agreement between the City of Vancouver and the Municipality of Delta has extended the operation of the landfill until 2037 with a remaining capacity of 20 million tonnes as of Oct. 1, 1997. The Vancouver Landfill footprint covers about 225 ha with approximately 400,000 tonnes of municipal refuse deposited each year. The landfill serves a population base of 853,045 residents and associated businesses (1998 figures) from the areas of Vancouver, Delta, Richmond, University Endowment Lands (UEL), White Rock and a portion of Surrey. As stipulated in the B C Environment "Landfill Criteria for Municipal Solid Waste", a final cover must be  installed on a municipal solid waste landfill following closure. The design requirements include a soil barrier layer with a maximum hydraulic conductivity of l x l 0 " cm/s, above 5  which is soil with approved vegetation. The primary function of a final cover is to limit percolation of rainwater into the waste thereby reducing the production of leachate. The term "final" cover implies that the cap that is installed following closure will remain in perpetuity. Due to the long functional life requirement of a final cover, other issues besides a hydraulic barrier function, must be considered in the design. These include: reducing erosion caused by wind or rain, gas collection or removal, eliminating vector attraction/penetration, The Vancouver Landfill  1  Final Closure Strategy  accommodating settlement and aesthetic acceptance. Attainment of the multiple functions required by the final cover system demands a multi-layer design approach. These layers can be divided into five main categories: surface layer, drainage layer, barrier layer, gas collection layer and foundation layer. Each layer has specific design requirements for optimal performance. Soil based materials with distinct characteristics (eg. grain size) or geosynthetic materials can be used in the construction of each of these layers. To aid the City of Vancouver in the design of a final closure strategy for the Vancouver Landfill, a research project was initiated. The goals of the project were to evaluate Lower Mainland soils with respect to construction of a low permeability barrier layer, and to investigate alternative material use, including geosynthetics. A key soil source that was focussed upon was material originating from trench excavations by City of Vancouver staff. If the material could be used in the construction of the final cover, this would serve as an inexpensive material source and would also solve disposal related issues. The proper closure of a municipal solid waste landfill requires general knowledge of final cover design principals and knowledge of site-specific considerations including regulatory requirements. Regulatory guidelines and final cover design options specific to the Vancouver Landfill are presented in chapter one. A general discussion of closure design principals for each of the layers within a cover system is also presented. Design and construction issues related to the installation of a hydraulic barrier layer, is described in detail. Included in this, is the development of physical criteria for selection of soil suitable for use in the construction of the barrier layer. One of the objectives of the research was to evaluate the suitability of Lower Mainland soils for use in barrier construction. The attainment of this objective was completed through a comprehensive literature review and the implementation of a program of sample collection and analysis. Information pertaining to this aspect of the study is presented in chapter two. A brief description of the geologic history of the area is followed by a comprehensive literature review of soil deposits and characteristics for the Lower Mainland region. Included in this section are surficial geology mapping, ocean disposal data and an agricultural based review of soil deposits. To further characterize Vancouver area soils, sample collection and analysis was conducted on material from large-scale excavation projects and trench excavations. From the combination of literature review and sample  The Vancouver Landfill  2  Final Closure Strategy  collection and analysis, soil sources suitable for use in the construction of a hydraulic barrier layer have been identified. Trench material was also evaluated for use in other areas of final cover design. Information regarding alternative material uses to soil from excavation projects is presented in chapter three of this report. Fraser River dredge material is briefly discussed, while the use of geosynthetics in final cover design is covered in detail. The major issues regarding the use of geosynthetic materials in barrier design are slope-stability, differential settlement and long-term performance. Based on these issues and site-specific considerations for the Vancouver Landfill, barrier material recommendations are given. The final chapter of this report provides for a discussion of the previously presented material and final conclusions. It is hoped that the information provided in this report will give insight into the complexities of final cover design and will aid the City of Vancouver in the successful closure of the Vancouver Landfill.  The Vancouver Landfill  3  Final Closure Strategy  2 OBJECTIVES The purpose of the research presented in this Thesis is to aid the City of Vancouver in the development of a final closure strategy for the Vancouver Landfill. The objectives of the research are as follows: •  Develop guidelines for acceptance of soil material for the construction of a hydraulic barrier layer in a municipal solid waste landfill cover. Selection criteria will include physical characteristics including grain size distribution and plasticity. In addition to the guidelines, will be recommended laboratory and field testing procedures. The completion of this objective will be a combination of literature review and laboratory testing.  •  Determine locations of potential borrow sources, in the Lower Mainland region, of soil material meeting soil selection criteria. A n extensive literature review combined with sample collection and analysis will be used to complete this objective.  •  Evaluation of City of Vancouver trench excavation material for use in the construction of final cover. The layer options include the barrier layer, drainage layer, surface layer and foundation layer. Material characterization will be completed by sample collection and analysis and evaluation based on literature specifications.  •  Investigate the use of alternative cover materials in final cover design. These alternatives include geosynthetic options. Material will be evaluated with regards to suitability and cost and recommendations made accordingly based on literature review.  The Vancouver Landfill  4  Final Closure Strategy  3 RESEARCH M E T H O D S To complete the outlined objectives of the Thesis required a stepwise system of literature review and sample collection and analysis. The development of a set of physical criteria for evaluating soil sources for suitability as hydraulic barrier construction material was the initial priority. Closure guidelines produced by the British Columbia Ministry of Environment, Lands and Parks (BC MoELP) recommend the final cover consist of a 1000 mm thick soil based barrier with a hydraulic conductivity less than 10" cm/s. The 10" cm/s 5  5  guideline is not based on results from hydraulic modeling, and therefore is meant to serve as a starting point in the design of a municipal solid waste landfill cover (Jim Atwater, personal communication). Lower values of barrier layer hydraulic conductivity may be required for a given landfill depending on issues such as adequate runoff and the economic cost of leachate collection and treatment. The use of alternative technologies is allowed in final cover design, assuming equivalency can be shown. No guidance is given by B C MoELP, with regards to soil characteristics, which would allow for the construction of the barrier layer. To secure the necessary physical selection criteria for soils, an extensive literature search was conducted. The main body of research originates in the United States where allowable hydraulic conductivities are more stringent than in B C . Soil selection criteria have been 7  5  developed to attain hydraulic conductivities less than 10" cm/s as opposed to the B C 10" cm/s guidelines. The set of physical criteria include maximum particle size, gravel content, fines (silt/clay) content, clay content and plasticity index requirements. Other parameters, which must be adequately addressed, include moisture content and compactive effort. Given the numerous variables impacting attained in-situ permeability, it is impossible to modify the US based criteria to give soil characteristics pertaining to barrier construction for hydraulic conductivities less than 10" cm/s. A n extensive amount of research would need to be 5  conducted to develop soil selection guidelines specific to the 10" cm/s hydraulic conductivity 5  value. Further, a consulting report by the engineering firm of Sperling Hansen Associates (SHA) investigated final cover barrier material options for the Vancouver Landfill. The recommendation from this report is that the barrier layer should have a hydraulic conductivity of less than 10" cm/s. This recommended value is closer to 10" cm/s and 6  7  supports the use of US guidelines to evaluate soil sources. In addition, the volume of soil material required to successfully cap the Vancouver Landfill is not available from a single  The Vancouver Landfill  5  Final Closure Strategy  borrow source in the Lower Mainland. Material originating from various types of excavation projects will have to undergo appropriate testing and subsequent stockpiling. A n anticipated high variability in both material types and characteristics of soil sources in the study area favors the use of a more conservative evaluation approach. Combining the permeability recommendation of 10" cm/s with the anticipated high variability of material characteristics, 6  the decision was made to evaluate soils based on US guidelines for the construction of a barrier layer with a hydraulic conductivity of less than 10" cm/s. The adoption and use of 7  the 10" cm/s soil selection criteria will allow for a more comprehensive evaluation of Lower 7  Mainland soils, as time will not be spent developing physical criteria specific to the attainment of 10" cm/s or 10" cm/s permeability values. However, the collected data is 5  6  presented in such a manner that it would be possible to complete a comparison with an alternative set of criteria should they be developed from future research. The maintenance of City of Vancouver infrastructure includes the excavation of soil materials for the placement of sewer-line piping systems. The excavated soil, historically, has been transported to the Vancouver Landfill where it is used for various purposes such as daily cover. As the soil from these trench excavations represents a substantial disposal cost to the City, the material was the first source evaluated for use in construction of the barrier layer. Soil samples were collected, analyzed and compared to the previously developed soil selection criteria. The locations that were sampled, were a function of where excavations were occurring at the time of the study. At the beginning of sample collection, trench excavations were concentrated in the eastern portion of the City. Near the end of sample collection, excavations had shifted west. A n effort was made to adequately characterize as many locations as possible, given time and laboratory space constraints. The initial findings from trench excavation analysis were not positive. In general, the soil material did not meet selection criteria as it contained large rocks and insufficient fines. As a consequence of these results, alternative soil sources were considered. The geologic history of the Lower Mainland region is dominated by a series of glaciation events. The surficial deposits of today are a result of those events. Surficial maps indicate that the majority of the City of Vancouver is covered by glacial till deposits. These deposits can contain a variety of particle sizes ranging from boulders to clay, depending on the source material and the depositional environment. Richmond is comprised primarily of sandy material from the historic  The Vancouver Landfill  6  Final Closure Strategy  deposition of Fraser River carried sediments and the formation of the Fraser River Delta. Areas east of the City, including Surrey and Langley, are comprised of glaciomarine deposits, which in general, are fine-grained materials. To characterize the soil types found in the Lower Mainland region, the use of geotechnical reports from various excavation projects was investigated. The use of these reports proved not to be feasible for a number of reasons. First, the sheer number of records makes the compilation of the available data a task which would take years to complete. Secondly, is the issue of access. Although records exist, finding meaningful data for a given area is extremely difficult. This is partially due to filing systems, which organize files based on project numbers and not location information. Thirdly, geotechnical records generally take the form of soil profiles with depth. Various layers are classified according to the Unified Soil Classification system, which although useful, does not allow for direct comparison of material characteristics with selection criteria. For the above reasons, the use of geotechnical records to evaluate Lower Mainland soils was not pursued. The focus shifted to finding easily accessible literature descriptions, which would allow for a more direct comparison to soil selection criteria. A disposal option available to excavation companies is the deposition of clean native tills in the ocean environment. The Ocean Disposal Program is monitored by Environment Canada and is permitted by Canadian law under the Canadian Environmental Protection Act (CEPA), Part VI. Only native till materials may be disposed of and only following adequate laboratory testing. Samples are collected within the upper 1 m of material and are tested for contaminants such as hydrocarbons. In addition, particle size analysis is conducted. Access to the ocean disposal records resulted in the characterization of native tills originating in the Downtown Core of Vancouver and for a portion of the Broadway Corridor, also in the City of Vancouver. Although the data collected during this phase of the research is valuable, the grain size distributions pertain to a thin layer (1 m) of material and may not represent soil material characteristics at greater depths. To investigate material characteristics with depth, a second phase of sample collection and analysis was conducted. Various excavation companies were contacted, and requested to notify when and where projects could be visited and sampled. The locations where soil investigations took place are a consequence of this process and therefore represent the areas where excavations were occurring during the time of the study. Two sites were visited in the Downtown Core, four in the Broadway Corridor  ine  V a n c o u v e r Lailunu  7  Final Closure Strategy  and one in Burnaby. To assess the suitability of soil sources outside the City of Vancouver, an agricultural based soil survey, published in 1981, was consulted. This report contains visual and laboratory based descriptions of soil profiles for much of the Lower Mainland region. The soil profile characteristics are described from the surface to a depth of approximately 2 m. Based on an understanding of the geologic history of the area and published surficial geology maps, the Municipalities of Surrey and Langley were focussed upon for potentially containing suitable material. A n alternative soil source to excavated material was briefly investigated. In conversations with the Miller Contracting Ltd., the topic of Fraser River dredging operations was raised. Through discussions, it became apparent that a potentially useful soil material was currently being discharged into the Fraser River during maintenance dredging operations. A n effort was then made to estimate volumes and to evaluate the material against selection criteria. The last objective of the Thesis research was to investigate the use of geosynthetic based materials in final cover design. A n extensive literature review was conducted considering issues specific to the Vancouver Landfill. In summary, the soil selection criteria are based on a body of research from the US and pertain to the construction of a barrier layer with a hydraulic conductivity of less than 10" cm/s. Soil 7  source evaluation initially focussed on City of Vancouver trench excavations. Alternative soil sources, including areas outside the City, were evaluated through a combination of literature review and sample collection and analysis. Finally, the use of geosynthetic based materials for final cover construction was investigated by an extensive literature review. The following chapters will describe, in detail, the results and conclusions reached, with regards to final cover design for the Vancouver Landfill.  The Vancouver Landfill  8  Final Closure Strategy  4 F I N A L  C L O S U R E  S E L E C T I O N  D E S I G N  A N D D E V E L O P M E N T  O F  SOIL  C R I T E R I A  4.1 Introduction The development of a closure strategy for a municipal solid waste landfill requires basic knowledge of engineering principals as well as adequate investigation of site-specific considerations. In this chapter, general final cover design issues will be discussed as well as issues specific to the Vancouver Landfill. These topics will include regulatory requirements, final landfill schematic as well as construction and cost evaluations of barrier layer installation. The development of soil selection criteria for barrier material is also covered in this chapter. 4.2 Overview of Regulations The Vancouver Landfill is regulated by the B C Ministry of Environment, Lands and Parks, under Permit PR 1611. The permit has been in place since October 31 , 1973. st  Currently, the permit is in the final stages of being replaced by a new Operational Certificate MR-01611. The new Operational Certificate is based, in part, on principles outlined in "Landfill Criteria for Municipal Solid Waste" (Ministry of Environment, Lands and Parks,  1993), as well as on numerous site-specific considerations. The "Landfill Criteria for Municipal Solid Waste'''' are not regulations but they do provide guidelines for development, operation and closure of landfills in British Columbia. In addition to the provincial regulations, the Vancouver Landfill must also comply with municipal bylaws enforced by the District of Delta and by Sewer Discharge regulations under permit No. SC-1121 enforced by the Greater Vancouver Sewerage and Drainage District. In designing final closure strategies, local, provincial and federal regulations must be considered. Key regulatory requirements, taken from the above regulations, which affect design options at the Vancouver Landfill are summarized below (SHA, 2000): •  A closure plan detailing all elements of closure shall be prepared at least six months prior to closure of the landfill. The plan shall include information regarding: • estimated total waste volumes and tonnages, and the closure date; • a topographic plan showing the final elevation contours of the landfill and surface water diversion and drainage controls;  The Vancouver Landfill  9  Final Closure Strategy  • design of the final cover including the thickness and permeability of the barrier layers and drainage layers and information on topsoil, vegetative cover and erosion prevention controls; • procedures for notifying the public about closure and alternate waste disposal plans; • rodent and nuisance wildlife control procedures; • proposed end use of the property after closure; • a plan for monitoring groundwater surface water, landfill gas, erosion and settlement for a minimum post closure period of 25 years; and • a plan for the operation of any required pollution abatement engineering works such as leachate and landfill gas collection/treatment systems for a minimum post closure period of 25 years. •  Progressive closure shall be implemented at the Vancouver Landfill. Each completed phase shall be covered within one year of completing the subject area.  •  The final cover barrier layer shall consist of a minimum of 1.0 meter of low permeability (<lxl0" cm/s) compacted cap (or equivalent technology). 5  •  The barrier layer shall be protected with a minimum 150 mm thick topsoil layer with approved vegetation established.  •  Final cover shall be sloped at a minimum of 4 % to promote surface water runoff.  •  Surface water runoff shall be directed outside of the leachate collection system.  •  Landfill side slopes shall not be steeper than 3H: 1V.  4.3 Closure Design and Cost Analysis - Sperling Hansen Associates In January of 2000, the engineering firm of Sperling Hansen Associates prepared the report entitled "City of Vancouver Landfill Design and Operations Plan". This document  presents a design/operations/closure strategy for the City of Vancouver with respect to future operations of the site. The recommendations made in the report were developed in accordance with the Greater Vancouver Regional District (GVRD) Solid Waste Management Plan, the Draft B C Ministry of Environment, Lands and Parks (MoELP) Operational Certificate MR-01611 and with the spirit of the MoELP 1993 Landfill Criteria for Municipal Solid Waste. The preliminary closure plan for the Vancouver landfill, developed by SHA,  The Vancouver Landfill  10  Final Closure Strategy  was designed to achieve specific closure objectives. These closure objectives are outlined as follows: •  Isolation of refuse to prevent direct contact with humans and vectors.  •  Minimization of infiltration and leachate production through diversion and runoff.  •  Prevention of leachate breakouts at landfill toe and on side slopes.  •  Protection of the cover from erosion through maintenance of a sustainable vegetative community.  •  Enhancement of landfill gas collection by preventing upward venting of landfill gas and downward intrusion of oxygen from the atmosphere.  •  Attainment of the potential for redevelopment of the landfill for some beneficial end use.  As stated previously, a recent agreement with the Municipality of Delta has extended the operational life of the Vancouver Landfill until 2037 with a remaining capacity of 20 million tonnes of refuse as of Oct. 1, 1997. To accommodate this volume of refuse plus daily and intermediate cover soil, construction demolition waste, road materials and final cover, a total of 31.5 million m of air space will be required assuming a compacted waste density of 0.87 3  tonnes/m (SHA, 2000). To provide the desired air space, and limit waste placement to the existing landfill footprint, SHA designed a landfill with final contours that will attain a maximum elevation of 39 m (following closure, pre-settlement). Side slopes from the landfill toe to the slope break at the landfill crest will be built to 4H:1V, while grades on the landfill crest will be constructed at 5% (Figure 1). Figure 1: Vancouver Landfill Final Contour Schematic  Note: Not to scale  The landfill will be developed in nine phases starting at the eastern perimeter, switching to the western perimeter and then filling in the middle. The final landfill footprint, which will undergo waste placement, is projected to be 147.5 ha. A further 40 ha area on the western  T " L _  me  i.cn  11  v a u c u u v c i i^anumi  11  i r  T  T?"  1 /-ii  cu  i  Final Closure Strategy  perimeter o f the l a n d f i l l site w i l l not receive a d d i t i o n a l waste a n d is e x p e c t e d to be c l o s e d a n d c a p p e d b y 2 0 0 2 . S H A estimated c o n s t r u c t i o n m a t e r i a l requirements for e n v i r o n m e n t a l c o n t r o l systems, l a n d f i l l operations a n d infrastructure. T o t a l quantity o f R o a d B a s e m a t e r i a l (150 m m M i n u s ) is estimated to be 9 5 6 , 0 2 5 m  3  w h i l e R o a d M u l c h (19 m m M i n u s ) quantities  are estimated to total 2 1 3 , 0 3 3 m o v e r the l i f e o f the site. S o i l material requirements for 3  c o n s t r u c t i o n o f the f i n a l c o v e r o v e r the a p p r o x i m a t e l y 187.5 h a site h a v e a l s o b e e n estimated. T h e quantities listed b e l o w ( T a b l e 1) are a s s u m i n g a 3 0 0 m m top s o i l layer, a 2 0 0 m m drainage layer, a 1000 m m barrier layer, and a 300 m m gas c o l l e c t i o n layer. T h e gas c o l l e c t i o n l a y e r w o u l d o n l y be p l a c e d o n the side slopes. T A B L E 1: FINAL C O V E R M A T E R I A L  REQUIREMENTS  Layer  Thickness (mm)  Volume (m )  300 200 1000 300  568,315 378,877 1,894,384 205,434  Top Soil Drainage Barrier G a s Collection (side slopes only) (Ref: SHA, 2000)  a  T h e r e are m a n y o p t i o n s a v a i l a b l e to the engineer i n the d e s i g n o f a m u n i c i p a l s o l i d waste l a n d f i l l c o v e r . T h e d e c i s i o n whether to incorporate natural s o i l or geosynthetic materials w i l l be a f u n c t i o n o f m a n y s i t e - s p e c i f i c c o n d i t i o n s . I f b o t h s o i l a n d geosynthetic materials are a v a i l a b l e , one o f the m a j o r c o n s i d e r a t i o n s i n c h o o s i n g the appropriate c o n s t r u c t i o n m a t e r i a l w i l l be cost. A n e c o n o m i c a n a l y s i s s h o u l d c o m p a r e capital expenditures i n the actual c o n s t r u c t i o n o f the f i n a l c o v e r as w e l l as the i m p a c t o f a p r o p e r l y f u n c t i o n i n g barrier o n leachate c o l l e c t i o n a n d treatment costs. S H A i n c l u d e d i n their report to the C i t y o f V a n c o u v e r , cost a n a l y s i s f o r the c o n s t r u c t i o n o f four types o f c o v e r designs. A p p r o x i m a t e unit costs w e r e determined for e a c h o f the f o u r c o v e r systems based o n actual c o n s t r u c t i o n costs e x p e r i e n c e d b y S H A o n l a n d f i l l c l o s u r e projects throughout B . C . , cost estimates p r o v i d e d b y v a r i o u s suppliers i n the L o w e r M a i n l a n d , a n d actual material a c q u i s i t i o n costs e x p e r i e n c e d b y V a n c o u v e r L a n d f i l l staff. T h e first o p t i o n is a s o i l based c o v e r s y s t e m w i t h a barrier l a y e r , w h i c h has a n i n - s i t u h y d r a u l i c c o n d u c t i v i t y o f < l x l O " c m / s . A b o v e the barrier 6  layer i s a 2 0 0 m m t h i c k drainage l a y e r and a 3 0 0 m m t h i c k t o p s o i l layer. B e n e a t h the barrier layer i s a 3 0 0 m m t h i c k gas c o l l e c t i o n layer, w h i c h has b e e n separated f r o m the barrier l a y e r b y geotextile. B o t h the geotextile a n d gas c o l l e c t i o n l a y e r are i n s t a l l e d o n l y o n l a n d f i l l side slopes. T h e c o s t / n i for construction o f this c o v e r s y s t e m is estimated to be $ 1 6 . 4 0 . T h e  The Vancouver Landfill  12  F i n a l C l o s u r e Strategy  second cover system option is the use of a P V C geomembrane as the primary barrier layer. Above the geomembrane is a 200 mm thick drainage layer and a 300 mm thick topsoil layer. Below the geomembrane is a 150 mm thick sand layer which is placed on the crest area only and a geotextile filter overlying a 300 mm thick gas collection layer (side slopes only). The estimated cost/m for this option is $15.36. The third option is a composite cover system 2  which utilizes a P V C geomembrane in combination with a low permeability compacted soil layer. Separating the geomembrane in compacted soil is a sand friction layer (25 mm thick). Above the geomembrane is 200 mm of sand (drainage layer) and a 300 mm thick topsoil layer. Below the low permeability compacted soil layer, for the side slopes only, is a geotextile and a gas collection layer (300 mm thick). The cost associated with Option 3 is estimated to be $18.40/m . The fourth and final option considered by SHA is a soil based 2  cover, with layering order and thickness as that of Option 1. The only difference between Option 1 and 4 is that Option 4 has a barrier layer constructed from city excavated soil and the hydraulic conductivity is < lxlO" cm/s as compared to < lxlO" cm/s for Option 4. A 5  6  lesser cost associated with using variable quality material from city excavations reduces the cost of this final cover option by five dollars to $11.40/m . The overall estimated closure 2  cost of construction of cover system Option 1 is $22.6 million, Option 2 is $21.3 million, Option 3 is $25.1 million and Option 4 is $16.4 million. These closure cost estimates account for inflation at 2% and future costs have been discounted back to 1999 dollars at a rate of 6%. See Tables 2-5 (modified from SHA, 2000). T A B L E 2: F I N A L C L O S U R E UNIT C O S T S - OPTION 1: L O W P E R M E A B I L I T Y SOIL B A R R I E R Functional Layer  Material  Thickness (mm)  Cost/m*  Seeding Top Soil Drainage Layer Primary Barrier Friction Layer Secondary Barrier Separation Layer G a s Venting Layer  Grass Seed / Tree Plant Biosolids/Sand 50:50 Dredged Sand Glacial Till None None Geotextile Crushed Concrete 19 m m  NA 300 200 1000 0 0 3 300  $0.70 $1.20 $2.00 $10.00 $0.00 $0.00 $0.94 $1.57  6  B  Total Cost Notes:  $16.40  B - Geotextile and Crushed Concrete applied to the sloped areas only. The cost/m is adjusted to reflect the fact that the crest area covers approximately 64% of the closure area.  The Vancouver Landfill  2  13  Final Closure Strategy  TABLE 3: FINAL CLOSURE UNIT COSTS - OPTION 2: PVC GEOMEMBRANE COVER SYSTEM  Functional Layer  Material  Thickness (mm)  Cost/m  Seeding Top Soil Drainage Layer Primary Barrier Friction Layer Secondary Barrier Separation Layer Gas Venting Layer  Grass Seed / Tree Plant Biosolids/Sand 50:50 Dredged Sand PVC Geomembrane Sand Layer 150 mm None Geotextile Crushed Concrete 19 mm  NA 300 200 1 150 0 3 300  $0.70 $1.20 $2.00 $8.00 $0.96 $0.00 $0.94 $1.57  A  6  B  Total Cost  2  $15.36  Notes: A - Sand Layer applied to the crest area only. The cost//m is adjusted to reflect the fact that the crest area covers approximately 64% of the closure area. B - Geotextile and Crushed Concrete applied to the sloped areas only. The cost/m is adjusted to reflect the fact that the crest area covers approximately 64% of the closure area. 2  TABLE 4: FINAL CLOSURE UNIT COSTS - OPTION 3: PVC/CLAY COMPOSITE COVER SYSTEM  Functional Layer  Material  Thickness (mm)  Cost/m  Seeding Top Soil Drainage Layer Primary Barrier Friction Layer Secondary Barrier Separation Layer Gas Venting Layer  Grass Seed / Tree Plant Biosolids/Sand 50:50 Dredged Sand PVC Geomembrane Sand Layer 25 mm Glacial Till 300 mm Geotextile Crushed Concrete 19 mm  NA 300 200 1 25 300 3 300  $0.70 $1.20 $2.00 $8.00 $1.00 $3.00 $0.94 $1.57  6  6  Total Cost Notes:  2  $18.40  B - Geotextile and Crushed Concrete applied to the sloped areas only. The cost/m is adjusted to reflect the fact that the crest area covers approximately 64% of the closure area  TABLE 5: FINAL CLOSURE UNIT COSTS - OPTION 4: MOELP TYPE SOIL BARRIER  Functional Layer  Material  Thickness (mm)  Cost/m  Seeding Top Soil Drainage Layer Primary Barrier Friction Layer Secondary Barrier Separation Layer Gas Venting Layer  Grass Seed / Tree Plant Biosolids/Sand 50:50 Dredged Sand City Excavated Soil None None Geotextile Crushed Concrete 19 mm  NA 300 200 1000 0 0 3 300  $0.70 $1.20 $2.00 $5.00 $0.00 $0.00 $0.94 $1.57  6  Total Cost Notes:  B  2  $11.40  B - Geotextile and Crushed Concrete applied to the sloped areas only. The cost/m is adjusted to reflect the fact that the crest area covers approximately 64% of the closure area.  The Vancouver Landfill  14  Final Closure Strategy  Cost of construction of the final cover is not the only consideration when deciding on design options. More expensive cover solutions, i f installed properly, will result in a higher rate of clean water diversion and therefore lower leachate conveyance and treatment costs. To accurately determine the best cover design, leachate collection and treatment must be considered. SHA examined combined closure and leachate collection and treatment costs for the four previously outlined cover options. The costs were estimated based, over the operating life span of the facility and a 25-year post closure period. The results of the analysis are listed below in Table 6: T A B L E 6: E S T I M A T E D F I N A L C L O S U R E C O S T S C o s t ($ million) Option Option Option Option  1 2 3 4  33.1 31.6 34.0 33.9  (Ref: S H A , 2000)  Again the above cost estimates have been discounted back at the rate of 6 % to 1999 and have accounted for inflation of 2%. From this analysis is it evident that the lowest overall cost (including leachate treatment collection) would be provided by Option 2 (PVC geomembrane) at a cost of $31.6 million. Option 1 (low permeability soil) gives the second least cost solution at $33.1 million. Although the cost analysis conducted by SHA indicates that the least cost solution is the construction of a final cover using a P V C geomembrane as the barrier layer, unit costs were estimated based on today's values. If in the future, cost for leachate collection and treatment, were to increase, the more expensive composite cover system (Option 3) may make more economic sense. Economic predictions are important in the design of municipal solid waste landfill final covers, however they should be viewed with caution and re-evaluated on a regular basis. 4.4 Approach to Design of Final Cover As directed by government regulations, following the closure of a municipal solid waste landfill, a final cover or cap must be installed. The primary function of the final cover is to limit infiltration of water into the waste, thereby reducing leachate production. The British Columbia government guidelines specify a hydraulic conductivity of l x l 0 " cm/s as 5  being the maximum allowable for a hydraulic barrier layer. There are currently two  T l -  -  ine  i r  Vancouver  T  J.C11  j_,aiiuiin  1  u  C  1 /-<i  C U  j.  rmai Closure Strategy  fundamentally different viewpoints on the amount of water that should be allowed to enter a closed landfill. The first is an "entombment" procedure, where drainage systems are optimized and the hydraulic barrier layer has such a low permeability that water essentially does not enter the waste. The breakdown of organic material occurs slowly over time resulting in low levels of methane generation, slow settlement rates and overall, a longer post-closure monitoring/management time period. The opposite viewpoint is that of rapid stabilization, which allows water to enter the waste at levels that will enhance organic material breakdown. Leachate recycling or recirculation can be a component of this type of closure strategy. Rapid stabilization results in high levels of methane generation, large settlement rates and overall, a reduced post-closure monitoring period. A further function of the final cover is that it should be aesthetically pleasing. Depending on where the landfill is located, this could mean a grass cap, an asphalt covered surface or a rip-rap top being visible to the public eye. Other basic requirements, of the landfill final cover are, an ability to resist erosion by wind or rain, accommodate settlement, and eliminate vector attraction or penetration. At some landfill sites a gas collection and removal system may also be required. Due to the wide array of final cover functions, the design method is of a multi-layered system. Each layer within the system serves singular or multiple purposes resulting in a final cover which is able to meet all of the previously mentioned functions. The multi-layered approach can result in final cover designs, which are quite basic to very complex. Figure 2 is a schematic of a generalized cover and shows the basic layers which can be found. From the top-down is the surface layer, a protection layer, a drainage layer, a barrier layer, a gas collection layer and a foundation or base layer. The surface layer and protection layer are usually combined and discussed as a single layer in the cover system. Separating each of the above layers may be necessary depending on the potential movement of particles between layers. Separation can be accomplished by using soil or geosynthetic materials.  The Vancouver Landfill  16  Final Closure Strategy  Figure 2: Generalized Final Cover S Id ILL  1  1\LT l U l J  Mill l  I LL W ILS)  X' ' Hydraulic/Gas Bainer Layer (geomembrane ' \ compacted clay liner and/or geosvnthciic clay liner) ' t  :Gas/6ollection;Layer.<(soil:or/geosynthetic.):-.  ^  ^  ^  ^  ^  ^mmmmmm ^ ^ ^ ^ ^ ^  w m m m m m m m m m m m ( Modified from Koerner et al., 1997)  4.4.1 SURFACE LAYER (VEGETATIVE) The vegetative layer is an integral component of the landfill final cover system. The functions of the surface (vegetative) layer are to support vegetation thereby reducing erosion and promoting evapotranspiration, be aesthetically acceptable, reduce vector attraction and protect underlying layers. In the case of the Vancouver Landfill, plant growth will be established in order to prevent erosion and to allow the landfill, in its closed state, to blend in with the surrounding landscape. B.C. Ministry of Environment Lands and Parks specifies that the topsoil layer should be a minimum of 0.15 meters in depth while SHA recommends a minimum, 0.30 meters depth to provide adequate moisture retention which will reduce plant mortality and the risk of root penetration into the underlying barrier layer. Since plant growth will occur in the surface layer, material selection will be that of a loamy soil which contains appropriate levels of organic matter and plant nutrients. The choice of type of vegetation is a function of the climate as well as speed of growth and growth pattern. Plants that have deep penetrating roots are not appropriate for landfill covers as they pose a risk to compromising the underlying barrier layer. Fast-growing species, which are not adversely affected by landfill gas, are recommended, as they can be quickly established to reduce The Vancouver Landfill  17  Final Closure Strategy  erosion. SHA recommends that closed areas should be seeded during late summer or fall with an appropriate mix that includes native grasses and nitrogen fixing legumes, as well as fast-growing species such as fall rye. A seed mixture specified by SHA on other closure contracts in the Lower Mainland and used widely by the Ministry of Transportation and Highways is Terrasol Mix TEC 825, which consists of: •  25% Boreal Creeping Red Fescue Grass  •  15% Tall Fescue Grass  •  15% Climax Timothy Grass  •  17% Dahurain Wild Ryegrass  •  3% Redtop  •  10% Dwarf White Clover  •  5% Rangelander Alfalfa  •  10% Birdsfoot Trefoil  Note: % are given on a weight basis  The seed mix should be applied at a rate of 110 kg/ha. If seeding in the fall, a cover crop of fall rye should be added to the mix at 105 kg/ha (SHA, 2000). Further recommendations given by SHA include: •  Addition of slow release fertilizer may be desirable in the seed mix, depending on nutrient deficiencies in topsoil mix.  •  Utilization of a hydroseeding application method with mulch, humectant and tackifier instead of conventional agricultural seeding methods should also be considered to minimize erosion in the critical first winter.  •  In the long-term, tall fast-growing grasses should be avoided due to the potential increased fire hazard during periods of drought.  The establishment of communities of trees on the closed landfill site can be accomplished to introduce biodiversity and improve the visual characteristics of the landfill. The concerns of root penetration and windfall can be reduced by increasing the soil thickness above the barrier layer to more than 1,000 mm, and planting only shrubs and trees with shallow, wide spread, rooting systems. Tree species recommended by SHA are listed in Table 7.  The Vancouver Landfill  18  Final Closure Strategy  TABLE 7: RECOMMENDED TREE SPECIES FOR USE AT LANDFILL SITES Recommended  Not Recommended  Maples (Acer spp.) Alders (Ainus spp.) Paper Birch (Betula papyrifera)* Trembling Aspen (Populus tremuloides) Dogwood (Cornus spp.) Ponderosa Pine (Pinus ponderosa) Black Cottonwood (Populus balsamifera)* Lodgepole Pine (Pinus contorta var. latifolia) Willows (Salix spp.)* Douglas Fir (Pseudotsuga menziesil) Western Hemlock (Tsuga heterophylia)* Western Red Cedar (Thuja plicata)* *Other considerations may impact location or applicability. (SHA, 2000)  4.4.2 DRAINAGE LA YER Under certain conditions, a drainage layer may be installed beneath the vegetative layer. The function of this layer is to convey water quickly and efficiently down landfill slopes to constructed ditches. This removal of water serves to reduce the hydraulic head placed on the barrier layer and to stabilize the upper vegetative layer against saturation, preventing potential slumping or slope failure. For proper drainage to occur, a minimum slope of 2 to 4 percent is recommended. During design, the effects of landfill settlement must be adequately addressed to ensure minimum slope values are maintained. This will reduce the negative impacts of surface ponding, which can be, slow vegetation growth and higher levels of water entering the waste. EPA (U. S. EPA, 1991) recommends a minimum hydraulic conductivity of lxlO" cm/s, while SHA suggests a value of lxlO" cm/s. To 2  1  adequately handle anticipated rainfall events, SHA (2000) also recommends the minimum thickness of the drainage layer should be 200 mm. Either soil based or geosynthetic materials can be used in the design of the drainage layer. Soil material would consist of a high percentage of gravel size material with few fines. Geosynthetic use in this area is becoming more popular as improved products are being developed. Geosynthetic materials will be covered in greater detail in following sections. 4.4.3 BARRIER LAYER The barrier layer is an integral component of a MSW landfill cover. The purpose of this layer is two-fold. To reduce water from entering the waste and to impede the movement of generated landfill gas to the atmosphere. The maximum allowable hydraulic conductivity specified by MoELP is lxlO" cm/s. SHA, on the basis of Help modeling techniques, 5  recommends a hydraulic conductivity of lxlO" cm/s (SHA, 2000). Historically, clay based 6  The Vancouver Landfill  19  Final Closure Strategy  materials have been used in the construction of the barrier layer, including soils classified as C L , C H and SC by the unified soil classification system (Daniel et al., 1995). More recently, the use of geosynthetic materials, such as geomembranes and geosynthetic clay liners, has become popular in areas where natural soil material is unavailable. In recent years, the majority of projects completed in North America (-80%) have used P V C geomembranes. The Hartland Landfill in Victoria and Cedar Road Landfill in Nanaimo, British Columbia have had successful installation of P V C geomembranes (SHA, 2000). The properties and uses of geosynthetic material in final cover design will be covered in greater detail in further sections of this report. A further option for material use is that of bentonite ammended soil. Key construction issues are material selection, placement and compaction, and post-construction protection. For the use of natural soil, material selection can be based on criteria such as grain size distribution and Atterberg Limits. Specifications can focus on maximum allowable particle size, gravel content, fines content and even clay content. Other material specifications, which must be considered during construction, are moisture content and allowable clod size. In the following section, natural soil material specifications will be discussed. British Columbia guidelines for barrier design specify a maximum allowable hydraulic conductivity value of 10" cm/s. This value is not based on results from hydraulic 5  analyses and therefore is only a guideline to aid the design process (Jim Atwater, personal communication). The hydraulic conductivity value of 10" cm/s recommended by SHA 6  (2000) was reached based on Help modeling and economic analysis of leachate collection and treatment, specific to the Vancouver Landfill. A n extensive literature review failed to establish material specifications for the construction of a barrier layer with permeability values less than 10" cm/s or 10" cm/s. The 5  6  majority of research conducted to develop material specifications originates in the United States where allowable values of hydraulic conductivity are more stringent than in British Columbia. As a result, the following specifications are in the context of building a soil liner with an in-situ hydraulic conductivity of less than 1x10" cm/s. For a natural soil liner to achieve a low hydraulic conductivity, the soil must contain a sufficient amount of fines. Fines are defined as the fraction of soil that passes the openings of the No. 200 sieve (0.075 mm). The fines fraction can be further subdivided into silt and  The Vancouver Landfill  20  Final Closure Strategy  clay sized particles. Clay sized material is defined as particles < 0.005 or < 0.002 mm with the 0.002 mm definition more common. Silt sized particles therefore range in size between 0.075 mm and either 0.005 or 0.002 mm depending on the clay definition chosen. The measurement of the clay sized fraction of the soil can be time-consuming. The most common laboratory technique is hydrometer analysis ( A S T M D-422), which utilizes settlement principals. Clay minerals are, for the most part, platelike in shape, behave like colloids and have a large surface area. The basic building blocks of the crystalline structure of a clay mineral is the silica tetrahedron and the aluminum octahedron (Figure 3). Figure 3: Basic Building Blocks of Clay Minerals  A silica tetrahedron and a silica sheet  An octahedron and an octahedron sheet  Q  and ( ) Hydroxyls 0  Aluminum, magnesium  G = gibsite (aluminum sheet) B=brucite (magnesium sheet)  (b)  (Modifiedfrom Oweis et al, 1998)  The engineering properties of clays are a result of the chemical structure of the minerals and of the interaction of these minerals with water. The three main clay minerals of importance  The Vancouver Landfill  21  Final Closure Strategy  are kaolinite, illite and montmorillonite. Kaolinite crystal layers consist of tetrahedron and octahedron sheets that are held together by hydrogen bonds. Its properties are a low swelling potential, low liquid limit, low activity and hydraulic conductivity values of 10" cm/s or 6  higher (Oweis et al., 1998). Illite consists of an aluminum sheet between two silica sheets with bonding between building blocks facilitated by potassium ions. The characteristics of illite are a moderate swelling potential, a liquid limit higher than kaolinite, and a hydraulic conductivity of 10" cm/s or lower. Illite is considered to be good material for clay liner 7  construction. The smectite group, which includes montmorillonite, is built from the same building blocks as illite but no potassium ions are present. The bonds holding together the sheets are Van der Waals forces and exchangeable ions. This makes the bonding between sheets very weak and can be easily broken by water. As a result, swelling potential, activity and liquid limit are the highest in this group of clays. The high swelling potential of this material can be beneficial in liner construction as it gives the material "self healing properties". Cracks in the constructed liner can be sealed as the material swells with the addition of water. A high swelling potential can also be detrimental, as drying of the clay will result in shrinkage crack development. Also, clay material such as montmorillonite can be difficult to work with in the field, as with added moisture the material becomes very sticky and mucky. A n additional concern is the lower shear strengths of clay based material which are compacted at wetter than optimum moisture contents. This can influence slope stability analysis. Slope stability will be discussed in greater detail in following sections. The amount and type of clay material determines whether a soil is plastic or non-plastic. Plasticity refers to the capability of the material to behave as plastic, moldable material. Plasticity characteristics are quantified by three parameters: •  Liquid Limit (LL)  •  Plastic Limit (PL)  •  Plasticity Index (PI)  The liquid limit is defined as, the water content corresponding to the limit between the liquid and plastic states of consistency of the soil. The plastic limit is defined as, a water content corresponding to the limit between the plastic and solid states of consistency of the soil. The plasticity index is the numerical difference between liquid and plastic limits, ie. PI = L L - P L . Plasticity parameters can be measured fairly easily and quickly. For this reason, most  The Vancouver Landfill  22  Final Closure Strategy  material specifications will require a minimum amount of fines together with a range of acceptable plasticity index values. The theory behind this is that these two selection criteria together will ensure that enough clay material, with appropriate characteristics, will be present to allow for the construction of a low hydraulic conductivity liner. Soil selection criteria taken from an E P A publication (1991) report minimum fines of 20 % combined with a plasticity index between 10 to 35 %. A publication produced by Daniel and Koerner (1995) suggest a minimum of 50 percent fines and a plasticity index requirement in the range of 10 to 40 percent. Further, Daniel (1990) recommended soil liner materials contain at least 30 percent fines. On the other end of the particle size spectrum is the issue of maximum allowable particle size. Criteria are dependent on the location of the soil liner within the overall cover system. For example, i f a geomembrane was to be placed on top of a compacted soil liner, the allowable maximum particle size would decrease to reduce the risk of puncture damage to the geosynthetic material. Specifications, where geomembranes are not an issue, allow for stones and rocks no larger than 2.5-5.0 cm to be contained in the soil (EPA, 1991; Daniel et al., 1995). Gravel content is another soil selection criteria that must be considered. Gravel is defined as material that is retained on the No. 4 sieve (4.76 mm). Some studies have shown that gravel can be uniformly mixed with a clayey soil up to 50-60 percent (dry-weight basis) without significantly increasing the hydraulic conductivity of the soil (Shakoor et al., 1990 and Shelley et al., 1993). Daniel et al., (1995) suggest that > 50 percent of gravel is unacceptable. E P A (1991) list acceptable material selection to have < 10 percent gravel content. The key issue with gravel content is adequate mixing of the materials so that pockets of gravel do not exist, and having sufficient fines to fill voids. Some gravel content can be beneficial in terms of maximizing strength and bearing capacity of the soil liner. From the literature values, it seems evident that the fewer the fines the less allowable gravel content. Vice versa, a high clay based material can withstand the addition of greater gravel contents. Table 8 summarizes soil selection criteria for a soil barrier layer in a M S W landfill final cover, based on literature recommendations. Soil material meeting the selection criteria can be compacted to achieve hydraulic conductivity values less than 10" cm/s. This is under 7  the assumption that compaction will be conducted at moisture contents wet of optimum.  TI. _ x r  T  i n n  m c vaiicouveiLcuiumi  i o  ZJ  T?:  i /~<i  ru  4.  rinai Closure ouaiegy  T A B L E 8: S U M M A R Y O F L I T E R A T U R E R E C O M M E N D E D SOIL S E L E C T I O N CRITERIA  Fines (dry-weight basis) Clay Content (dry-weight basis) Plasticity Index Percentage of Gravel (dry-weight basis) Maximum Particle Size  EPA, 1991  Daniel et al., 1995  > 20 % N/A 10-35% < 10% 2 . 5 - 5 cm  > 30 - 50 % 10-20% 10-40% Dependent on soil, > 50 % unacceptable 2.5 - 5 cm  4.4.3.1 Moisture Content and Compactive Energy Physical characteristics of the natural soil are not the only parameters, which dictate whether suitably low hydraulic conductivities can be obtained by compaction. Other factors including molding water content, compactive effort and post construction protection influence the overall function of the soil barrier layer. For natural soils, moisture content at the time of compaction is perhaps the single most important variable that controls the engineering properties of the compacted material (Daniel et al., 1995). Figure 4 shows the typical relationship between molding water content and hydraulic conductivity. Figure 4: Effect of Molding Water Content Upon (a) Dry Unit Weight; and (b) Hydraulic Conductivity  (B) Hydraulic Conductivity  (A) Compaction Curve  ft I  >  e  =>  fc-  a  >» x Molding Water Content  (Ref: Daniel etal.,  Molding Water Content  1995)  Soil material compacted at the optimum water content will have the greatest dry unit weight for that particular material under given compaction standards. Soil compacted wet of optimum tends to have low hydraulic conductivity and low strength. Conversely, soils compacted dry of optimum, tend to have relatively high hydraulic conductivity values. For soils with high plasticity index values molding water content is very important. The soils, when dry, form clods which are difficult to break and mold together. Figure 5 shows a  The Vancouver Landfill  24  Final Closure Strategy  highly plastic soil (PI = 41%) compacted at one percent dry o f optimum, and the same soil compacted with the same effort at three percent moist o f optimum (Daniel et al., 1995). Figure 5: Highly Plastic Soil Compacted with Standard Proctor Effort at Water Content of (a) 16% (1% Dry of Optimum) and (b) 20% (3% Wet of Optimum)  (a)  (b)  16% (1% Dry o f Optimum)  20% (3% Wet o f Optimum)  (Ref: Daniel e t a l . , 1995)  The differences are clearly visible. For the soil sample compacted dry o f optimum, large voids are present due to clay clods that could not be re-molded with the compactive effort used. If soil is to be compacted on the dry side o f optimum, clay clods should be reduced i n size to minimize interparticle voids. E P A (1991) suggests the use o f a road reclaimer (also called a road recycler) which pulverizes material with teeth that rotate on a drum at a high speed. Water contents much greater than optimum values are also not recommended, as the shear strength o f the material w i l l be reduced to potentially unacceptable levels and there is a greater risk o f the formation o f desiccation cracks as the soil liner dries out. Adequate testing of selected soil material is required to accurately determine an acceptable range o f moisture content values which w i l l result i n a l o w hydraulic conductivity barrier following compaction. Type o f compaction and compactive energy are other issues which influence the attained in-situ hydraulic conductivity o f a soil liner. Soil liners are constructed in loose lifts, of a maximum o f 225 mm (9") in depth, prior to compaction. The selected soil is placed in  FJnol f l  the loose lifts, compacted and process repeated until the specified thickness of liner is completed. Most soil liners are constructed with "footed" rollers, where the "feet" penetrate the loose lift of soil, breakdown clods and remolds the soil into a homogeneous mass. This type of compaction method is termed kneeding and is highly effective for plastic soils (Daniel et al., 1995). The "feet" length can very, with short feet (-100 mm or 4") called "pad foot" rollers and long feet (-200 mm or 8") often called "sheepsfoot" rollers. The depth that the rollers penetrate the loose lift of soil influences the degree of bonding between lifts. Proper bonding is essential to minimize zones of high hydraulic conductivity at interfaces between lifts, which provide hydraulic connection between more permeable zones in adjacent lifts. Sheepsfoot rollers that penetrate through the loose lift into the previously compacted lift aid in the bonding process. Roughening of a previously compacted lift prior to placement of new soil also aids bonding. This can be accomplished by a disking the soil to approximately 2.5 cm depth (EPA, 1991). Greater energy of compaction, remolds clods of soil, realigns soil particles, reduces the size or degree of connection of the largest pores in the soil and lowers hydraulic conductivity. The hydraulic conductivity of the soil that is compacted wet of optimum could be lowered by one to two orders of magnitude by increasing the energy of compaction, even though the dry unit weight of the soil is not increased measurably (EPA, 1991). In the field, compacted energy is controlled by (Daniel etal., 1995; EPA, 1991): a) the weight of the roller (greater weight produces more compactive energy) b) the thickness of a loose lift (thicker lifts produce less compactive energy per unit volume of soil) c) the number of passes of the compactor (more passes produce more compactive energy) The choice of equipment used, loose lift of thickness and number of passes is dependent on the moisture content of the soil and the firmness of the foundation layer. Heavy rollers cannot be used if the soil is very wet or the foundation is weak and compressible. The rollers with static weights of at least 13,608 to 18,144 kg (30,000 to 40,000 pounds) are recommended for compacting low hydraulic conductivity layers in cover systems (EPA, 1991). Heavier equipment is available but may not be suitable due to the presence of compressible material (waste) a short distance below the cover. The number of passes of  T l - _ 1  J  T  i uc v ancouver L,anuim  26  Final Closure Strategy  equipment will very, but at least 5 to 10 passes are usually required to deliver sufficient compactive energy (EPA, 1991). 4.4.3.2 Desiccation Cracking Drying of a compacted soil liner can be disastrous as cracks can form resulting in greater than anticipated hydraulic conductivity values. This is especially true in cover systems where the thickness of soil overlying the barrier layer is relatively thin, resulting in low confining stresses. Desiccation cracks in the liners under low confining stresses tend to be more permeable than liners under high confining stresses (EPA, 1991). Soil applies an overburden stress of approximately 1 psi per foot of depth (EPA, 1991). So, for the final cover design proposed by S H A where a topsoil layer (300 mm thick) over lies a drainage layer (200 mm thick) which in turn over lies a barrier layer (1000 mm thick), a confining stress of approximately 2-5 psi is anticipated. In a study by Boynton and Daniel (1985) large compressive stress (> 8 psi, or 56 kPa) closed desiccation cracks that had previously formed and in combination with hydration of the soil, essentially healed the damage done by desiccation. Regardless of the anticipated confining stress for barrier layers in final covers, care must be taken not to allow desiccation to occur during construction and post construction. This can be accomplished by frequent watering of the soil during construction and placement of soil or a geomembrane over the completed barrier layer during the time between placement of the vegetative layer or drainage layer. Due to heat generation, black pigmented geomembranes are not recommended for placement on top of a clay barrier layer if soil material is not to be placed immediately on top of the geomembrane. If a geomembrane is to be used, wind conditions must also be considered. Air-flow under the geomembrane will dry out the underlying clay layer and defeat the purpose of placement of the geomembrane in the first place. Three case studies of field performance of barrier layers in test plots were reviewed by Daniel (1995). The three studies discussed were the Omega Hills Landfill near Milwaukee, Wisconsin, Kettleman Hills located in an arid part of California and a landfill in Hamburg, Germany. The purpose of the test plots was to provide data on the performance of cover systems under realistic field conditions. Clay barrier layers were covered with either soil or a geomembrane or a combination of both. The case studies indicated that the only practical way to protect a low hydraulic conductivity compacted soil liner from desiccation from the surface is to cover the soil liner with both a geomembrane  TL. w  T  irrn  i n c v a n c u u v c i i^aiiuuii  "tn  rv  z/  r m m ^lOSUTe  i  cu 4.  Strategy  and a layer of cover soil. Soil covering alone would be required to be extremely thick in order to attain sufficient protection of the soil liner. If soil materials are used in the construction of the barrier layer, SHA recommends that the soil be placed and compacted on the dry side of optimum. The choice of compaction on the dry side of optimum is based on SHA field experience and is recommended to minimize desiccation cracking. The previously outlined, recommended soil selection criteria (Table 8) are given under the assumption that soils meeting the criteria will be compacted at water contents slightly wet of optimum. If recommendations by SHA are followed, and soils meeting the given criteria are compacted dry of optimum, required values of hydraulic conductivity may not be achieved. Unacceptable levels of hydraulic conductivity could result due to inadequate re-molding of clay clods and subsequent void formation. Although SHA recommends compaction dry of optimum, no information is provided with regards to material selection under these conditions. The choice to compact dry of optimum will require the development of different soil selection criteria to that given in this report. The development of a new set of criteria will require extensive laboratory and field testing to assure the attainment of suitably low levels of hydraulic conductivity. 4.4.3.3 Slope-Stability Stability of soil and geosynthetic materials on landfill side-slopes is a major area of concern during and after construction of a final cover system. The potential consequences of a slope failure can be disastrous both environmentally and economically. The potential shear plane is generally linear, parallel to the slope angle and along the surface having the lowest interface shear strength. Limit equilibrium principles are used, for the most part, in the analysis of final cover slope failure problems. The use of limit equilibrium analysis requires the determination of material specific, shear strength properties, and the subsequent calculation of interface friction angles. For clay materials, the determination of shear strength properties can be conducted under drained or undrained conditions. In a total stress analysis, drainage during a shear test is not allowed to occur and the assumption is made that the pore water pressure and therefore the effective stresses in the test specimen are identical to those in the field. The results of a total stress analysis are interface friction angles based on undrained shear strength properties of the soil. In an effective stress analysis, the influence of pore water pressure is considered, and interface friction angles are based on  The Vancouver Landfill  28  Final Closure Strategy  drained shear strength properties (Holtz et al., 1981). To effectively evaluate slope stability in a landfill final cover, interface friction angles should be determined using both a total stress analysis and an effective stress analysis. Once interface friction angles are determined, a factor of safety can be calculated. For the simplest case, that of drained conditions and a translational failure, the equation used to calculate a factor of safety is: FS -  tan (friction angle) tan (slope angle)  (1)  Equation 1 is provided as a starting point in the evaluation of slope stability in landfill covers. In practice, this equation is not often used, as it does not address important issues, which influence slope stability. These issues include: •  a finite slope with the incorporation of a passive soil wedge in the analysis.  •  the incorporation of equipment loads on the slope.  •  the use of tapered cover soil thickness.  •  veneer reinforcement of the cover soil using geogrids or high strength geotextiles.  •  consideration of seepage forces in the cover soil.  •  consideration of seismic forces acting on the cover soil.  Modifications to the simple analysis outlined above can be made to address more complex final cover design issues. The complex analysis are beyond the scope of this Thesis, but please refer to Koerner et al., (1997) for a more detailed description. Regardless of the complexity of the equations, if the FS value is less than 1.0 there is a high probability that the slope will fail. For cohesionless soils, friction angles are seldom less than 26° or greater than 36° (ultimate strength) (Hough, 1969). Variation in this range may be related to particle size, shape, gradation and composition. For cohesive soils (clays) typical interface friction angles under drained shear tests, lie between 20-35°. The higher friction angles are usually associated with soils having a plasticity index between 5-10, while the lower values are associated with plasticity indexes of 50-100 (Sowers et al., 1961). For the side-slopes proposed for the Vancouver Landfill by SHA, a preliminary design factor of safety can be calculated using Equation 1. A 4H: 1V slope has an angle of 14° and if the 20° value for the drained friction angle of clay is used, then the FS value is 1.5. The strength of clay soils varies significantly with consistency (moisture content). A given clay near its liquid limit has no strength, whereas the same clay at successively lower water contents can acquire  The Vancouver Landfill  29  Final Closure Strategy  considerable amounts of strength. The construction conditions for a compacted soil barrier, which will result in the lowest hydraulic conductivity values (compaction wet of optimum) also decreases the internal friction angle of the soil. A balance must be met between achieving low hydraulic conductivity and maintaining adequate slope stability. The determination of interface friction angles must be obtained under both best and worse case conditions that are anticipated at the landfill, with the worst case being that of a fully saturated clay. Preliminary design can utilize literature values of soil shear strength, however final design requires adequate laboratory testing and even small-scale field trials to accurately determine a factor of safety. Slope stability and shear strength values for soil/geosynthetic and geosynthetic/geosynthetic interactions will be discussed in sections following. 4.4.3.4 Differential Settlement As waste material undergoes compaction due to self-weight and decomposition, a landfill will undergo settlement. Two types of settlement exist at M S W landfills, both of which can impact the performance of an engineered final cover. They are, total settlement and differential settlement. Total settlement is the total downward movement of a fixed point on the surface while differential settlement is measured between two points and is defined as the difference between the total settlements at these two points (EPA, 1991). A third term is also used to evaluate settlement. Distortion is defined as the differential settlement between two points divided by the distance along the ground surface between the two points (EPA, 1991). Differential settlement is considered to be much more critical with respect to proper functioning of the final cover than total settlement. The impacts of total settlement can be mitigated through accurate estimations and proper design. For example, drainage slopes are often initially constructed at steeper angles to accommodate settlement, with final slope grading of 2-4 % following settlement. Tensile strains develop in cover materials as a result of differential settlement. Tensile strain is defined as the amount of stretching of an element divided by the original length of the element (EPA, 1991). Tensile strains and bending stresses are a concern because of the potential for the soil material to crack. For the barrier layer, cracking can result in higher than anticipated in-situ hydraulic conductivity values. The amount of strain that a low hydraulic conductivity, compacted soil can withstand prior to cracking, depends significantly upon the water content of the soil. In general, soils  The Vancouver Landfill  30  Final Closure Strategy  compacted wet of optimum are more ductile than soils compacted dry of optimum (EPA, 1991). To maintain the soils ductile properties however, the soil cannot dry out. This point further enhances the importance of proper post-construction care of a compacted clay liner to reduce both the development of desiccation cracks and cracking due to differential settlement. Table 9 gives values for published tensile strains at failure for various cover materials. T A B L E 9: C O M P I L A T I O N O F P U B L I S H E D T E N S I L E STRAINS A T F A I L U R E F O R C O V E R MATERIALS  Type or Source of Soil Natural Clayey Soil Bentonite Illite Kaolinite Portland Dam Rector Creek Dam Woodcrest Dam Shell Oil Dam Willard Test Dam Embankment Gault Clay Balderhead City Clay Kaolin Clay A ClayB ClayC Needle-punched G C L Geotextile encased stitchbonded G C L Bentonite geomembrane composite G C L Geomembrane biaxial bending Sand-bentonite mixtureno overburden, no significant cracking (Ref: Oweisetal., 1998)  Water Content  Plasticity Index (%)  Maximum Tensile Strain (%)  19.9 101 31.5 37.6 16.3 19.8 10.2 11.2 16.4  7 487 34 38 8 16 Non-plastic Non-plastic 11  0.80 3.4 0.84 0.16 0.17 0.16 0.18 0.07 0.20  19-31 10-18 21-30  39 14 32 16  0.1-1.7 0.1-1.6 1.3-2.8 2.8-4.8  16-29 19-33 18-26  31 49 32  1.5-4.1 1.6-3.6 1.7-4.4 5-16 5  -  30 20-100 4  The data presented in this table indicates that soil material can fail at tensile strains as low as 0.1 percent. This value of tensile strain translates into a maximum allowable value of distortion (delta/L) of approximately 0.05. This value of distortion was obtained from a  The Vancouver Landfill  31  Final Closure Strategy  graph generated by Gilbert and Murphy (1987), which shows the relationship between tensile strain in a cover and distortion (Figure 6). Figure 6: Relationship Between Tensile Strain and Distortion ( A/L)  1.0 0.8 0.6 _i  0.4 0.2 0.0 .1  1  10  100  Tensile Strain (%) (Ref: Gilbert et al., 1987)  To appreciate how much differential settlement will give the distortion value of 0.05, assume a circular depression develops in a cover system with a radius of three meters. Distortion = differential settlement between two points length between points 0.05  =  delta 3m  delta  =  15 cm  Therefore, a settlement at the center of the depression > 15 cm could result in cracking of the soil layer. Geomembranes can generally withstand far larger tensile strains without failing than soils (EPA, 1991). Settlement associated with waste consolidation proceeds relatively rapidly when compared with the process of waste decomposition. Experience at other sites in British Columbia has shown waste settlement to be typically 2 % per year (SHA, 2000). The situation at the Vancouver Landfill however, is a bit more complex due to the presence of compressible soils beneath the landfill. Geological mapping completed by the Geological Survey of Canada indicates that the Vancouver Landfill was developed in an area of lowland T l - . - IT  T  i n e vaucouvei i^aiiuim  1 /"ll  11  T7:  J Z  r i n a i v^iusuie o u a i e g y  Clj  .1  peat. The peat overlies Fraser River deposits, which in this vicinity, are described as overbank (or floodplain) sandy silt and silt loam, normally less than two meters thick. This layer overlies deltaic and distributary channel fill deposits which are 10 to 25 m thick and consist of interbedded fine to medium sand with occasional silt beds. The geology of the Vancouver landfill is presented in detail in the " Vancouver Landfill Hydrogeological Review" (Gartner Lee Limited, 1995). The major findings of this report are summarized below. The site geology consists of four main horizons, with some local variation within each layer. The stratigraphy is: •  A layer of lowland peat, that is thickest in the north and thins to the southwest. The observed thickness of the peat ranges from 5.6 m in the north to 1 m in the southwest. Undisturbed peat typically comprises a 0.5 m layer of surficial fibrous material, overlying a 1 m transition zone, and a 1.5 to 4 m amorphous layer of well decomposed, plastic peat with discontinuous interbedded silt layers. The base of the peat layer is usually identified by an organic silt layer, that in turn grades into the underlying gray silt.  •  The gray silt layer ranges in thickness from 4.5 to 7 m beneath the landfill property, although thicknesses of 20 m have been observed near the apex of the Fraser Delta. The silts are flat lying, and were deposited during the sea level rise between 8,000 and 5,000 years BP. The silts grade from clayey silt near the top of the succession, into a sandy silt with depth, and contain thin sand interbeds near their base. The gray silt is underlain by medium gray sand.  •  The gray sand grades from a silty sand to a clean, medium gray sand within a few meters. The sand was deposited on the advancing delta prior to 8,000 years BP. The sand layer has an observed thickness of 10 to 30 meters beneath the site and overlies a massive, firm clayey silt layer.  •  The basal gray silt was deposited in the ancestral Straight of Georgia, likely beyond the delta, shortly after deglaciation. The lower silt layer is estimated to exceed 200 meters in thickness at the Vancouver landfill.  Due to the additional loading associated with waste and final cover placement, each of these layers will undergo additional settlement. Studies conducted at the Vancouver Landfill show a settlement rate of 6 % per year for a recently completed cell 12 meters in height (SHA, 2000). It is expected that this rate will decrease over time and that the value is elevated due to be presence of compressible soils. Theoretical analysis of landfill settlement has projected a value of 8 m of settlement within the underlying soil strata. This value was calculated  The Vancouver Landfill  33  Final Closure Strategy  based on the placement of waste material to the 39 m height, which is the anticipated maximum elevation, of a filled Vancouver Landfill (SHA, 2000). When the potential exists for large differential settlement, as is the case, at the Vancouver Landfill, the placement of a temporary cover (5-10 years) following closure should be considered. This is especially the case when leachate removal treatment systems are already in place. The purpose of a temporary cover would be to control infiltration of water but the impacts of differential settlement would not be as severe as repairs could be made (e.g. addition of soil material or grading) fairly easily. Once the majority of settlement has occurred the permanent final cover would be installed. The placement of cover material on a more stable foundation layer would result in better long-term performance of the final cover. Most regulations governing landfill operations stipulate the final cover be installed shortly following closure of the landfill. The potential for amending the regulations, assuming all environmental concerns are met, should be investigated by landfill operations management on site specific basis. 4.4.4 GAS COLLECTION LA YER  At some municipal waste landfills, the management of gases, generated from the decomposition of organic waste materials, may include the construction of a gas collection layer. The purpose of this layer is to collect gases (mainly methane) to reduce potential explosion hazards and odor problems. Sand, gravel, geonet, geotextiles or geocomposites, are examples of the various materials that can be used in the construction of the gas collection layer. Gas collection can be done in a passive or active manner. A passive system is one where the movement of gases is gradient controlled only, while an active system pumps gas from depth to the surface where it can be flared or utilized as a fuel. The permeability requirement of the gas collection layer is dependent on the anticipated amount and rate of gas production. For the Vancouver Landfill, a permeability of l x l 0" cm/s or 1  greater is recommended by SHA to prevent head buildup. Separation of the gas collection layer from soil material above and below, may be required to prevent small particle migration and subsequent clogging. Geotextiles are often used in this situation.  The Vancouver Landfill  34  Final Closure Strategy  4.4.5 FOUNDA TION LA YER  The last component of the final cover system is the foundation or base layer, which overlies the waste. Intermediate or daily cover soil generally comprises this layer. Thickness can be variable, depending on the time of placement. For example, additional material may be added to an area of the landfill that has undergone differential settlement, prior to the placement of the final cover. The main functions of this layer are to separate the final cover components from the waste and to form a relatively stable base on which to compact and place final cover materials. 4.4.6 SUMMARY  The design and construction of a M S W landfill final cover can be a complex process. Many variables must be taken into consideration in the specifications of design of various layers with often opposite functions. Other structural issues, which impact design, are differential settlement, slope stability and construction on a variable subbase (waste). Historically, soil based materials have been used in the construction of landfill covers. Much data exists with respect to the behavior of soil materials and therefore they are often the construction material of choice, i f available. The recent evolution of geosynthetic materials makes these products a viable alternative to the use of soil. 4.5 Hydraulic Conductivity Laboratory Testing 4.5.1  BACKGROUND  Hydraulic conductivity analysis is a critical step in the evaluation of soil sources for the construction of barrier layers, either in liner or cover systems of engineered landfills. Permeability of natural soil materials can be extremely varied. Table 10 gives typical hydraulic conductivity values for various materials. It should be noted that variation exists between material types and within a given material type. For example, till materials have listed hydraulic conductivities ranging between l x l O " to 2X10" cm/s (Hasan, 1996). 10  The Vancouver Landfill  35  4  Final Closure Strategy  T A B L E 10: H Y D R A U L I C C O N D U C T I V I T Y O F E A R T H M A T E R I A L S  Material  Hydraulic Conductivity (cm/s)  Sediments  Gravel Coarse sand Medium sand Fine sand Silt, loess Till Clay Unweathered marine clay  3x10" - 3 9xl0- -6xl0"' 9xl0" - 5xl(T 2xl0" -2xl0Ixl0" -2xl0Ixl0- -2xl0" Ixl0" -4.7xl02  5  5  2  5  2  7  3  10  4  9  8x10"" - 2 x l i r  7  7  Sedimentary Rocks  Karst and reef limestone Limestone, dolomite Sandstone Siltstone Salt Anhydrite Shale  belt) -2 lxlO" - 6X10" 3xl0" - 6x10* lxlO" - 1.4xl0" l x l O " - lxlO" 4x10" - 2 x l 0 ' lxlO" - 2 x l 0 " -4  7  4  8  9  10  8  11  6  11  7  6  Crystalline Rocks  Permeable basalt Fractured igneous and metamorphic rock Weathered granite Weathered gabbro Basalt Unfractured igneous and metamorphic rock (Modified from Hasan, 1996)  4xl0" -2 5  8xl0" -3xl0 3.3xlCT -5.2x10' 5.5x10 - 3.8x10" 2xl0" -4.2x10 7  2  7  -5  9  3xl0  _12  3  4  -5  -2xl0"  8  Many factors influence the permeability of a given soil including the physical properties of the soil and testing procedure employed. Some of these factors include grain size distribution, soil density, degree of saturation and applied hydraulic gradient.  Examples of  laboratory procedures are the variable head test and the constant head test, with permeameters being rigid wall or flexible wall. The influence of grain size distribution and density (degree of compaction) on hydraulic conductivity has been covered previously. The influence of soil saturation and applied hydraulic gradient will now be briefly discussed in the context of laboratory testing.  The Vancouver Landfill  36  Final Closure Strategy  The greatest measured permeability value for a soil under a given set of testing parameters will be when the soil is fully saturated. This is because air-filled voids in an unsaturated soil effectively block water flow and subsequently reduce measured permeability values. Saturation of a compacted soil sample can be a difficult and time-consuming process. To obtain a high degree of saturation, Daniel (1994) recommends the use of de-aired water, with permeation continuing until outflow and inflow rates are equal and until hydraulic conductivity is steady. This process, for soils having hydraulic conductivities < l x l 0 " cm/s, 7  can result in testing times of 1 -8 weeks for a given sample. Although testing times are increased, the accurate determination of maximum hydraulic conductivity requires saturation of the sample. In the engineered landfill environment, hydraulic gradients associated with liner and cover systems are expected to be low, given the installation of functioning drainage systems and proper slope design. For laboratory testing, the use of low hydraulic gradients does not allow for the completion of tests within a reasonable time period. However, the use of high gradients can result in un-reliable values of hydraulic conductivity. For example, high gradients can alter the sample volume or nature of the void system and may also cause particle migration resulting in clogging or loss of material by erosion (Oweis et al., 1998). The hydraulic gradient employed during laboratory testing must balance the need for reasonable testing times and the need for reliable results. Overall, the accurate determination of the hydraulic conductivity for a given soil sample can be a time-consuming and expensive process. As many factors influence soil permeability, care must be taken to mimic, as closely as possible, anticipated field conditions, so that meaningful results can be obtained. In addition, the understanding of the limitations of laboratory testing and the potential influence of these limitations on results is critical in proper barrier design and construction. Although laboratory determination of hydraulic conductivity is important, field tests should be conducted to assure that selected soil material can be compacted to achieve required permeability values. The test pad should be built using the same loose lift thickness, type of compactor, weight of compactor, operating speed, and minimum number of passes that are proposed for the actual barrier layer. The most common method of measuring in situ hydraulic conductivity in test pads is the sealed double-ring infiltrometer. The hydraulic conductivity analyses conducted during  The Vancouver Landfill  37  Final Closure Strategy  this Thesis research were performed under sample size, economic and time limitations. The purpose of the testing was to ascertain whether soil samples meeting selection criteria could be compacted to achieve suitably low levels of permeability. Given the limitations of the testing, the generated results should be viewed as ballpark estimations. 4.5.2 TESTING METHODS  Minimal laboratory testing of soil samples meeting selection criteria was carried out to determine if suitably low values of hydraulic conductivity could be achieved. Soilcon Laboratories performed hydraulic conductivity analyses on supplied soil samples. The procedure used (provided by Soilcon) is outlined below: The Standard Proctor compaction specifications used to prepare the soil cores are as follows: Wt. of hammer (lbs.)  # of soil layers  Ht. of hammer drop (inches)  # of blows per layer  Compactive energy per volume (ft-lb per cubic ft)  5.5  3  12  25  12,400  The first layer is compacted in the 4" mold and then a 4.75 (ID) by 2 (H) cm core is placed in the center and tapped into the first layer. The subsequent layers were compacted above this first layer. The technician compacted the sample at approximately the optimum moisture content of the sample, based on past experience working with various soils. The small core is carefully removed from the large mold by using a small trowel to dig around it. Once it has been removed, it is carefully shaved flush to the edge of the soil core. Saturated hydraulic conductivity is performed on the prepared soil core using a falling head soil core method (Klute and Dirksen 1986). The soil is wetted to saturation and water flows through the sample under a falling head of water. Water flows through from the bottom to top of the soil core in order to remove any trapped air pockets. The sample is allowed to equilibrate prior to recording the conductivity readings. 4.5.3 RESULTS  The results of hydraulic conductivity measurements are given below. Two samples were chosen, trench excavation material from the site of Granville St. and 4 Ave., and a th  sample collected at a large-scale project at 4 Ave. and Burrard St.. Grain size distribution th  data and resulting hydraulic conductivity measurements are listed in Table 11.  TT.  _  me  ^  T V a n c o u v e r  jmi juanuiiii  T  38  Final Closure Strategy  T A B L E 11: H Y D R A U L I C C O N D U C T I V I T Y R E S U L T S  Location Granville St. and 4  % gravel % sand % silt % clay th  Ave.  12.9  45.8  26.5  14.8  % fines Ksat (cm/s) 41.3  1 reading  2.5xl0-  st  2  reading  2.2x10"  7  3  rd  reading  l.OxlO"  7  4  th  reading  1.3xl0'  7  5 reading A v e . and Burrard St.  1.2xl0" 3.2x10"  th  4  th  7  nd  7  2.4  52.5  35.3  9.8  45.1  8  Soilcon Laboratories compacted the samples at approximately optimum moisture content (determined by experienced lab personnel) using standard proctor effort. For the sample collected at Granville St. and 4 Ave., hydraulic conductivity values decreased over the time th  period measurements were taken. The initial saturated permeability (Ksat) value was 2.5xl0" cm/s while the fifth reading was 1.2xl0" cm/s. According to the lab technician 7  7  performing the analysis, the decrease in permeability over time is an indication of swelling clays in the sample. Prior to testing, the sample contained 12.9% gravel (no rocks > 2.5 cm in diameter) and 41.3% fines, of which 14.8% was clay sized material. The second sample tested (4 Ave. and Burrard St.) contained 2.4% gravel (no rocks > 2.5 cm in diameter), th  45.1% fines (9.8% clay) and had a saturated hydraulic conductivity of 3.2xl0" cm/s. 8  Consecutive readings for this sample were stable. The results from these analyses indicate that soil material meeting the minimum soil selection criteria can be compacted to produce low hydraulic conductivity values. 4.6 Summary Recent agreements between the Municipality of Delta and the City of Vancouver have extended the operational life of the Vancouver Landfill to 2037. Closure will occur in progressive stages as the existing landfill footprint is filled in. Side-slopes are to be constructed at 4H:1V to a height of 29 m. The landfill crest will be constructed at a grade of 5% extending to the final height of 39 m (pre-settlemenf). Total settlement at the Vancouver Landfill is anticipated to be quite large due to the presence of highly compressible soils beneath the waste. Theoretical analysis has projected a value of 8 m of settlement within the underlying soil strata (SHA, 2000). Final cover design can range from simple to complex, in the attainment of various functions. The basic layers of a final cover system include a  The Vancouver Landfill  39  Final Closure Strategy  surface layer, a drainage layer, a barrier layer, a gas collection layer and a foundation layer. A n integral component of the final cover design is the barrier layer. Both geosynthetic and soil based material options exist for the construction of this layer. Cost analysis indicates that the least expensive barrier material option is the use of a P V C geomembrane. The second least expensive option is soil material attaining a hydraulic conductivity less than 10" cm/s. Cost analysis included leachate collection and treatment. Other issues affecting 6  material choice for the barrier layer are differential settlement, side-slope stability, desiccation cracking (clay) and soil material availability. To assess the suitability of soil deposits in the Lower Mainland region, a set of physical criteria has been developed, based on literature recommendations from a body of work originating in the United States. Table 8 summarizes the soil selection criteria. Soil material meeting these specifications can be compacted to achieve hydraulic conductivity values less than 10" cm/s, according to U.S. 7  EPA. This is assuming adequate compactive effort is applied at moisture contents slightly wet of optimum. Two soil samples were given to Soilcon Laboratories for hydraulic conductivity testing. The purpose of this testing was to confirm the ability of local soil material, meeting selection criteria, to be compacted to achieve low values of permeability. The testing procedures utilized were dependent on sample size and equipment limitations, and time constraints. As a consequence of these limitations, the Ksat results should be viewed as ballpark approximations and not precise measurements. The physical characteristics of the two soil samples tested were < 15% gravel, no rocks > 2.5 cm in diameter, > 30% fines and clay contents meeting the 10% minimum requirement. The samples were compacted at moisture contents close to optimum and the resulting saturated hydraulic conductivity values were < lxlO" cm/s. The general conclusion from this testing 6  is that local material meeting barrier selection criteria can be compacted to achieve suitably low values of hydraulic conductivity.  The Vancouver Landfill  40  Final Closure Strategy  5 SOIL MAPPING 5.1 Introduction The evaluation of soil sources in the Lower Mainland region, for use in construction of a hydraulic barrier layer was a key component of the Thesis research. The approach to evaluation was a combination of literature review and the implementation of sample collection and analysis. The first type of literature information considered for use in the evaluation of Lower Mainland soils was Geotechnical reports. The use of these reports for the general evaluation of soils proved not to be feasible for reasons which will be discussed later in this chapter. A general description of surficial deposits in relation to geologic history and depositional environment was provided by Armstrong (1984) and mapping published by the Geological Society of Canada. This body of work supplied the first layer of information on soil sources in the Lower Mainland region, and aided in the preliminary identification of suitable soil sources outside the City of Vancouver. Further characterization of City of Vancouver soil was accomplished using Environment Canada Ocean Disposal Program records and sample collection and analysis of trench excavations and large-scale excavation projects. Trench excavation material was targeted as a potential borrow source, as it currently presents, both disposal and economic issues for the City. Ocean disposal data is concentrated in the downtown core of Vancouver and represents the upper 1 m of native till at each site. As this information only represents a small fraction of large-scale excavation profiles, sample collection and analysis was conducted at various locations to assess changes in material characteristics with depth. The evaluation of soil sources outside the City of Vancouver was conducted, using information presented in a report by Luttmerding (1981). The report provides agriculturally based soil profile characterizations as well as grain size and plasticity data. The results and conclusions of the assessment of Lower Mainland soils, for the construction of a hydraulic barrier layer, are presented in the following chapter.  The Vancouver Landfill  41  Final Closure Strategy  5.2 Literature 5.2.1 REGIONAL  Review SETTING  The Canadian portion of the Fraser Lowland occupies the southwest corner of the Pacific Coast mainland with an area of approximately 2600 square kilometers. It is bounded on the north by the Coast Mountains, the southeast by the Cascade and Chuckanut Mountains and on the west by the Straight of Georgia (Figure 7). Figure 7: Map of Fraser Lowland  (Ref: Armstrong, 1984)  Both the Coast and Cascades are major mountain systems with summits in excess of 1800 meters. Deep, U-shaped glacial valleys, many of which terminate in fiords (Howe Sound, Indian Arm), divide the Coast Mountains. Fiord lakes are also present in the area (Pitt and Harrison Lakes). Examples of glacial valleys which terminate in the Fraser Lowland are the Fraser River Valley between Rosedale and Hope, which separates the Coast and Cascade Mountains, and the western part of the Chilliwack River Valley in the Cascade Mountains. The Fraser Lowland is dominated by the Fraser River, which occupies a late-glacial and post-glacial valley up to five kilometers wide and 225 meters deep. The river empties into the Straight of Georgia after crossing a delta, which is approximately 31 kilometers long and 20 kilometers wide. The river has the third largest average mean flow in Canada. At Hope: average annual mean flow is 2700 m /s; during spring runoff (May, June) mean flow 3  ranges between 7000 and 12,000 m /s. The Fraser River has a length of 2800 km and 3  The Vancouver Landfill  42  Final Closure Strategy  transports a heavy load of sand/silt and clay with the sediment derived in a large part from its basin north of Lytton, 105 km north of Hope. North and south of the Fraser River Valley, the Fraser Lowland consists mainly of gently rolling and flat-toped uplands, separated by wide, flat-bottomed valleys. Most of the upland areas consist of unconsolidated deposits, do not exceed 175 meters in elevation, and range in area from 3 to 400 square kilometers. Also a number of bedrock hills or mountains rise above the main lowland area, for example Burnaby Mountain, Grant Hill, and Sumas Mountain, all above 300 meters in elevation. In addition to the Fraser River Valley, two other valleys transect the Fraser Lowland: Nickomekl and Sumas valleys, both of which were arms of the sea during the period from 13,000 to 11,000 years ago. The Nickomekl Valley is more than 30 kilometers long and five kilometers wide and stretches from Boundary Bay northeast to the Fraser River. The Sumas Valley also averages five kilometers in width and in Canada extends from the International Boundary north east 25 kilometers to the Fraser River. 5.2.2 CLIMATE  The climate of the Fraser Lowland is classified as inshore maritime and is strongly influenced by the Coast Mountains to the north and Cascade Mountains to the east. A strong increase in precipitation occurs from south to north and west to east with total precipitation varying from year to year. Mean annual precipitation values range between 950 mm in Ladner to 2900 mm at Holyburn Ridge (9 km northwest of Vancouver, elevation 950 m). The mean annual precipitation at the Vancouver Landfill is approximately 1,000 mm. There is considerable variation in the annual rainfall amount, however, with minimum and maximum annual rainfalls recorded as a 581 and 1403 mm respectively. The average monthly precipitation ranges from a maximum of 159 mm in December and January to a minimum of 27 mm in July. About 75 percent of annual total precipitation in the Fraser Lowland occurs during the months of October through March. Snowfall may occur anytime during the winter months, but is most likely in December, January and February. The average annual snowfall at the Vancouver Airport is about 45 cm, Abbotsford, 75 cm and Holyburn Ridge, 750 cm. Although rain dominates during the winter months, the period from April to September has frequent long spells of sunny weather. During this time, temperatures rarely exceed 30°C and overnight temperatures seldom drop below 10°C.  The Vancouver Landfill  43  Final Closure Strategy  5.2.3 REGIONAL  GEOLOGY  5.2.3.1 Bedrock Geology In downtown Vancouver, Tertiary sedimentary rocks are at or within a few meters of the surface. They consist of interbedded sandstone, siltstones, mudstones, shales and conglomerates. In places the sedimentary rocks are interlayered with, intersected by, or overlain by Tertiary basaltic volcanic rocks (eg. Queen Elizabeth Park). 5.2.3.2 Quaternary (Surficial Geology) The surficial geology of the Lower Mainland has been shaped by geologic processes, which have occurred in the distant past. Geologic history has shown that the area was subjected to repeated glaciations separated by non-glacial intervals. Each glaciation had three main stages: a) an advance stage, characterized by coalescing piedmont glaciers probably terminating in the sea. b) a maximum stage when the ice attained a thickness of 1800 meters or more and overode all the Fraser Lowland and much of the adjoining mountainous areas. c) a retreat or deglaciation stage when ice mainly occupied the valleys and arms of the sea once again. The present landscape and deposits are primarily the result of the last glaciation (Late Wisconsin) and post-glacial (Holocene) processes.  5.2.4 CLASSIFICATION  AND COMPOSITION  OF  DEPOSITS  The methods of transportation and the environment of deposition are the major factors that determine the physical makeup of the sediments. Three major groups of sediments comprise the bulk of the Fraser Lowland deposits: 1. Waterlain sediments transported by rivers and streams and deposited in either salt (marine) or freshwater. 2. Glacier ice sediments deposited directly on land as result of glaciation. 3. Glaciomarine and glaciolacustrine sediments, which are waterlain deposits, in which glacier ice transported material, has been dropped.  The Vancouver Landfill  44  Final Closure Strategy  In addition to the above, wind blown (eolian) and colluvial sediments are found in limited areas. Peat bogs and organic sediments are widespread in flat lying, lowland areas and are also found to a minor extent in upland areas.  5.2.4.1 Waterlain Sediments Waterlain material can be subdivided into fluvial, marine, lacustrine and glaciofluvial deposits. Fluvial deposits consist of stream channel and floodplain sediments and deltaic sediments normally deposited in the sea. Channel deposits along the Fraser River are most widespread. East of Mission these materials are sandy gravel. West of Mission they are sand interbedded with minor quantities of sand and silty loam. Fraser River overbank deposits are mainly silty to silty clay loam. Fraser delta deposits consist, in addition to the above, of thick sections of fine sand to clayey silt. Grain size analysis data of Fraser delta marine foreslope deposits, from 30 to 45 meters below sea level, taken from near Annacis Island in the New Westminster City area is reported by Armstrong (1984). The samples consisted of interbedded, soft to firm, gray clayey silt, and loose to compact fine sand. The six samples tested were composed of 62-67 % silt, 23-37 % clay, 1-12 % fine sand. X-ray diffraction of the clay fraction (< 2 um) showed: > 50 % muscovite mica, 30-50 % kaolinite, 10-30 % chlorite, < 10 % quartz, < 5 % montmorillonite. The rivers and streams flowing out of the Coast and Cascade Mountains normally carry much coarser sediments than does the Fraser River. Gravel and sand are deposited in their channels, floodplains and deltas. Glaciofluvial are the most widespread of the waterlain sediments. These materials have been transported and then deposited by meltwater streams flowing from advancing or wasting glacier ice. Channel, floodplain, deltaic and ice contact deposits are found within this group. Deltaic deposits consist of gravel, sandy gravel, and gravely sand. Ice contact deposits are poorly to well stratified drift, deposited in contact with melting glacier ice. These deposits may consist of a mixture of pebble to cobble gravel, containing clasts of glacier ice and glaciomarine sediments. 5.2.4.2 Glacier Ice Sediments Glacial till is defined as those sediments deposited directly on the land by glacier ice. They can be subdivided into lodgment (basal) (most common in Fraser Lowland), ablation (meltout) and flow tills. Lodgment till is deposited at the base of a glacier; ablation till is  The Vancouver Landfill  45  Final Closure Strategy  material largely carried within or on the surface of a glacier which melts out during deglaciation and settles on the land surface; flow till is formed in the terminal area of the glacier and is derived from ablation till which may become fluid during thawing of the ice and as a result, may move downslope as a liquid or a semi-plastic flow (Armstrong, 1984). Lodgment tills deposited by the Westlynn, Semiahmoo, Coquitlam, and Vashon glaciers are very compact, unsorted mixtures of sand, silt, clay, pebbles, cobbles and boulders. Pebbles, cobbles and boulders may comprise up to 50 % of the till, but commonly comprise < 25 %. Mechanical analysis of the fine fractions of lodgment till samples provided the following data (Armstrong, 1984): Westlynn till (1 sample) 9.2 % clay 49.5 % silt 44.3 % sand Semiahmoo till (3 samples) 8.6 % clay 42.3 % silt 49.4 % sand Vashon till (9 samples) occur widely at the surface in the western part of the Fraser Lowland 2.7 % clay 40.1 % silt 57.2% sand Ablation tills are non-compact deposits, which are widespread above elevations of 165 m where they overlie lodgment till. They contain < 5-10% silt and clay with the remainder being sand, gravel, and boulders. Flow tills identified in Vashon, Coquitlam, Fort Langley and Sumas ice contact deposits are similar in composition to lodgment tills with the degree of compactness varying with age, with younger being less compact. 5.2.4.3 Glaciomarine and Glaciolacustrine Sediments Glaciomarine sediments consist of stony silty clay loam, stony silt loam, stony silt and till-like mixtures. The composition of glaciomarine sediments (exclusive of till-like mixtures) are usually > 95 % clay, silt and sand: 10-50% clay 35-75 % silt 5-60 % sand  The Vancouver Landfill  46  Final Closure Strategy  Grain size analysis of drillhole specimens from Annacis Island are reported by Armstrong (1984): . - Capilano glaciomarine clayey silt (~ 65-80 m below sea level) 8 % fine sand 58 % silt 34 % clay - > 50 % montmorillonite 30-50 % chlorite 10-30 % kaolinite - Semiahmoo glaciomarine sediments (~115-120 m below sea level) 19% sand 38 % silt 43 % clay - > 50 % chlorite 30-50 % montmorillonite < 10% kaolinite < 10 % mica < 5 % vermiculite < 5 % quartz Glaciolacustrine sediments have limited distribution in the Fraser Lowland. They consist of varved clays, silts and sands, which contain scattered ice-rafted dropstones. 5.2.4.4 Colluvial Sediments Colluvial sediments include slide and fan deposits, which vary greatly in composition depending on the source materials. Eolian (windblown) deposits are widespread in areas where Sumas Drift is at or near the surface and consist of fine to well-graded sand and minor silt derived from Sumas Drift. They occur up to elevations of at least 450 m and probably higher in the Chilliwack map area. Organic deposits occur in Salish sediments, the Cowichan Head Formation and the Highbury Sediments. 5.2.4.5 Lowland Deposits Lowland areas within the Fraser Lowland can be subdivided into three types: a) delta of the Fraser River b) valley of the Fraser River c) valleys that were areas of marine sedimentation through much of their Quaternary history.  The Vancouver Landfill  47  Final Closure Strategy  The Fraser River Delta extends from New Westminster to the Straight of Georgia, 31 km long and up to 24 km wide. The sediments, which comprise the delta are post-glacial Fraser River sediments up to 200 m thick and consist of the following sedimentary sequence: -overbank sandy to clay loam (~2 m thick) -deltaic and distributary channel fill and floodplain sand and minor silt (up to 15m thick) -estuarine deposits - fine sand to clayey silt (up to 185 m thick) The Fraser River Valley is 1-5 km wide except in the vicinity of the Sumas and Pitt River valleys where it widens to 10 km. The valley floor reaches an elevation of 15 m at Rosedale (~100 km from the Straight of Georgia). Deposits laid down by the modern Fraser River (during the past 10,000-11,000 years) consist mainly of gravel and sand east of Sumas Mountain and sand and minor silt west of the mountain. Areas of marine sedimentation include the Nicomekl Valley, the Sumas Valley and the Lower Pitt River Valley. The Nicomekl Valley is greater than 30 km long and in places attains a width of 5 km. It extends from Boundary Bay, north east to the Fraser River. The floor of valley has a maximum elevation of 15 m and is underlain by marine silt, clay silt, and fine sand up to 300 m thick. The Sumas Valley which averages 5 km in width, lies between Sumas Mountain and Mount Vedder. It stretches from near Chilliwack, where it merges with the Fraser River Valley, southwest 30 km to the International Boundary. During much of the Quaternary it was an arm of the sea, while in Holocene time, it was occupied by a shallow lake which was drained in 1926. Post-glacial Sumas lake deposits are normally < 5 m thick and consist of fine sand, silt and clay. They overlie up to 300 m or more of silt, clayey silt and fine sand. The Lower Pitt River Valley is 8 km wide and is underlain by flood plain and overbank deposits of the Pitt and Fraser Rivers (up to 15 m thick). These deposits overlie up to 300 m of marine silt, sand, and clay of Capilano and pre-Capilano age. 5.2.5 SURFICIAL GEOLOGY  MAPS  Surficial geology maps of the Lower Mainland Region were generated by Armstrong and Hicock (1976), published by the Geological Survey of Canada (Maps 1486A and 1484A). The following discussion pertains to the information contained in these maps. See Figures 8 and 9 (oversized). Of the various types of surficial deposits found in the Lower Mainland region, some are considered as more suitable as barrier construction material than The Vancouver Landfill  48  Final Closure Strategy  others. For example Vashon till, as described by Armstrong (1984) for 9 samples, contains only 2.7% clay, which does not make this soil deposit suitable barrier construction material. Conversely, glaciomarine sediments such as Capilano, do contain sufficiently high clay contents (34% respectively), to be considered as suitable material. Accompanying the surficial geology maps are soil deposit descriptions, which can be used to initially identify those areas in the Lower Mainland where suitable material may be found. From these soil descriptions, the following deposits have been identified as containing potentially suitable material: Fort Langley Formation: F L d Capilano Sediments: Cd, Ce A full description of the Quaternary deposits found in the Lower Mainland is given below. These descriptions are taken directly from the legends which accompany the surficial geology maps published by the Geological Survey of Canada (Maps 1486A and 1484A), compiled by J.E. Armstrong and S.R. Hicock (1976). SAb-e: Bog, swamp, and shallow lake deposits SAb: lowland peat up to 8 m thick overlying Fb, Fc SAc: lowland peat up to 1 m thick, underlying Fb (up to 2 m thick) SAd: organic-rich sandy loam to clay loam 15 to 45 cm thick overlying Fd SAe: upland peat up to 8 m or more thick overlying V C units Fa-e: Fraser River Sediments Deltaic and distributary channel fill sediments overlying a cutting estuarine sediments and overlain in much of the area by overbank sediments. Fa: channel deposits, fine to medium sand and minor silt occurring along present day river channels Fb: overbank sandy to silt loam normally less than 2 m thick overlying 15 m or more ofFd Fc: overbank silty to silt clay loam normally less than 2 m thick overlying 15 m or more of Fd Fd: deltaic and distributary channel fill (includes tidal flat deposits), 10-25 m interbedded fine to medium sand and minor silt beds; may contain organic and fossiliferous material Fe: estuarine, fossiliferous, interbedded fine sand to clayey silt (sand content increases from bottom to top of sequence), 10-185 m thick Sa-e: Sumas Drift Outwash, ice-contact, and deltaic deposits. Sa: outwash sand and gravel up to 30 m thick  The Vancouver Landfill  49  Final Closure Strategy  Sb: ice-contact gravel and sand containing till lenses and clasts of glaciomarine stony clayey silt, 2-5 m thick overlying FLc,d Sc: ice-contact gravel and sand containing till lenses and clasts of glaciomarine stony clayey silt, 2-5 m thick overlying FLb,e Sd: ice-contact gravel and sand containing till lenses and clasts of glaciomarine stony clayey silt, more than 5 m thick Se: raised proglacial deltaic gravel and sand up to 40 m thick FLa-e: Fort Langley Formation Glacial and deltaic sediments. FLa: lodgment and flow till with sandy loam matrix containing clasts of FLc FLb: outwash and ice-contact gravel and sand containing clasts of Fla FLc: glaciomarine stony clayey silt to silty sand 8-90 m thick, commonly thinly bedded and containing marine shells FLd: marine silty clay to fine sand commonly containing marine shells FLe: proglacial deltaic gravel and sand Ca-e: Capilano Sediments Raised marine, deltaic, and fluvial deposits. Ca: raised marine beach, spit, bar, and lag veneer, poorly sorted sand to gravel (except in bar deposits) up to 10 m thick mantling older sediments and containing fossil marine shell casts up to 175 m above sea level Cb: raised beach medium to coarse sand 1-5 m thick containing fossil marine casts Cc: raised deltaic and channel fill medium sand to cobble gravel up to 15 m thick deposited by proglacial streams and commonly underlain by silty to silty clay loam Cd: marine and glaciomarine stony (including till-like deposits) to stoneless silt loam to clay loam with minor sand and silt, normally less than 3 m thick but up to 10 m thick in upland areas, containing marine shells. These deposits thicken from west to east. Ce: mainly marine silt loam to clay loam with minor sand, silt, and stony glaciomarine material (see Cd), up to 60+m thick. In many of the upland areas sediments mapped as Cc and Cd are mantled by a thin veneer (less than 1 m) of Ca VCa,b: Vashon Drift and Capilano Sediments Glacial drift including: lodgment and minor flow till, lenses and interbeds of substratified glaciofluvial sand to gravel, and lenses and interbeds of glaciolacustrine laminated stony silt; up to 25 m thick; in most places correlates with Va,b; overlain by glaciomarine and marine deposits similar to Cd, normally less than 3 m but in places up to 10 m thick. Marine derived (Ca) lag gravel normally less than 1 m thick containing marine shell casts has been found mantling till and glaciomarine deposits up to 175 m above sea level; above 175 m till is mantled by bouldery gravel that may be in part ablation till, in part colluvium, and in part marine. VCa: bedrock within 10 m or less of the surface VCb: bedrock more than 10 m below surface  The Vancouver Landfill  50  Final Closure Strategy  Va,b: Vashon Drift Till, glaciofluvial, glaciolacustrine, and ice-contact deposits Va: lodgment till (with sandy loam matrix) and minor flow till containing lenses and interbeds of glaciolacustrine laminated stony silts Vb: glaciofluvial sandy gravel and gravelly sand outwash and ice-contact deposits PVa-h: Pre-Vashon Deposits Glacial, nonglacial, and glaciomarine sediments. PVa: Quadra fluvial channel fill and floodplain deposits, crossbedded sand containing minor silt and gravel lenses and interbeds PVb: Quadra glaciofluvial deposits, deltaic deposits and crossbedded sand and gravel PVc: Quadra marine interbedded fine sand to clayey silt believed to be off shore equivalents of PVa PVd: Coquitlam till (glaciomarine?), and glaciolacustrine deposits PVe: Cowichan Head organic sediments PVf: Semiahmoo glaciomarine, glaciofluvial sediments and till PVg: Highbury fluvial, marine, and bog and swamp deposits PVh: Westlynn till and glaciomarine stony silty clay loam T: Tertiary bedrock including sandstone, siltstone, shale, conglomerate, and minor volcanic rocks; where bedrock is not exposed it is covered by glacial deposits and colluvium. The following discussion will focus on the types and locations of surficial deposits found in the Lower Mainland, as shown in Figures 8 and 9. Note: Capilano Sediments are mapped as 5 units (Ca-e), some of which are lithologic units only, and others take into account the thickness of the top unit plus the nature of the underlying sediments. In nonagricultural areas, Vashon Drift (V) and Capilano Sediments are commonly combined into one unit (VC). Normally the younger Capilano Sediments do not exceed 3 m in thickness. Vashon Drift is mapped as two units (Va-b) separated into sediments deposited primarily by ice and sediments deposited by meltwaters flowing from ice. The surficial geology of the Vancouver area is dominated by Vashon Drift and Capilano Sediments. For the most part VCb, with some areas, including the part of the downtown core, VCa. As well, there are some areas where Capilano Sediments are identified. A region of Cd (potentially suitable material) extends from Jericho Beach in a southeasterly direction to Trafalgar Park, which is located between MacDonald and Arbutus, near King Edward Avenue. The rest of the Capilano Sediments identified in the Vancouver area, are classified as Cb. The major outcrops occur, along South West Marine Drive between 49 Ave. and 70 Ave., around the Shaughnessy Golf Course again near South th  The Vancouver Landfill  th  51  Final Closure Strategy  West Marine Drive, an area approximately boardered by Granville-Cambie and 28 -42 th  nd  Ave, an area extending from 39 Ave. to South West Marine Drive and from around th  Cambie-Ontario. The last major outcrop of Capilano Sediments is boardered by Hastings & 1 Ave., and Nanaimo & Renfrew. The surficial geology of the Vancouver area does include st  some tertiary bedrock outcrops (T) (eg. Queen Elizabeth Park), some organic deposits (SAb-e) and other geologic deposits, however Vashon Drift and Capilano Sediments dominate. Burnaby, New Westminster and Coquitlam are also dominated by Vashon Drift and Capilano Sediments (VC). Simon Fraser University is constructed on a large tertiary bedrock (T) outcrop, organic deposits (SAb-e) can be found in and around Burnaby Lake, while PreVashon (PVa,b,e-h) deposits including glacial, non-glacial and glaciomarine sediments can be found to a limited degree around the intersection of North Rd. and Austin Avenue. Richmond and Delta are dominated in the western areas by Fraser River Sediments (Fa-e) and in the eastern areas by bog, swamp and shallow lake deposits (SAb-e). The surficial geology of Surrey is dominated by Capilano Sediments (Ca-d), with Cd predominating. Cd is considered as potentially suitable hydraulic barrier construction material. In and around the Nicomekl and Serpentine Rivers, bog, swamp and shallow lake deposits occur. Deposits of Vashon Drift also occur in the Surrey area, but to a limited degree. The Langley area can be subdivided into three regions of distinct geological deposits. The north western portion is covered in Capilano Sediments (Cd and Ce) while the south western area has a large outcropping of Sumas Drift (Sa-e). The eastern portion of Langley is dominated by the Fort Langley Formation (FLa-e), which includes glacial and deltaic sediments. Sumas Drift is also present in this area. To summarize the information provided in the surficial geology maps, the areas in the Lower Mainland region containing the thickest deposits of potentially suitable hydraulic barrier construction material are Surrey and Langley. These deposits are Capilano glaciomarine and marine deposits identified as Cd or Ce. The Vancouver area, in general, is comprised of glacial till deposits (Vashon Drift) which are thinly mantled by Capilano Sediments. One area in Vancouver is identified as containing Cd deposits, a zone extending from Jericho Beach to a southeasterly direction to Trafalgar Park.  The Vancouver Landfill  52  Final Closure Strategy  5.2.6 SOILS REPORT -H. A.L  UTTMERDING  Information regarding soil types and characteristics, for areas within the Lower Mainland, can be found in a 6 volume report published in 1981. The author, H. A . Luttmerding, summarizes years of research, which started in the late 1950s. The report, "Soils of the Langley-Vancouver Map Area" encompasses an area bounded on the west by the Straight of Georgia and on the east by a line passing north-south between Chilliwack and Sumas Canal (west longitude: 122° 00'). The south boundary is the U.S.-Canada border and the mapping extends north until 49° 30' north latitude. Soils are usually differentiated on the basis of characteristics to a depth of a meter or more. Soils exhibit a range of characteristics and properties and boundaries between different soils are not always clearly defined. As a consequence, the maps included in volumes one and two should be used as guides only, and should not take the place of site investigations. Some areas on the maps are identified as unclassified as when field surveys were performed, urbanization or industrialization had already occurred. Soils within the City of Vancouver have not been classified due to urbanization. Although much data is contained within the report, the classification of soil types in Surrey and Langley Municipalities will be the focus. The choice of these two municipalities is due to information shown on surficial geology maps (Armstrong and Hicock, 1976) and previously mentioned literature (Armstrong, 1984), which indicates that potentially suitable soil for the construction of a hydraulic barrier layer exists in the area. The maps of Surrey and Langley, produced by Luttmerding, show the presence of 53 different soils. A relationship exists between the classified soils and the surficial deposits from which the soil has formed overtime. Table 12, which is a modified version of that found in volume three of the report, shows this relationship for the soils identified in the Surrey and Langley map areas.  The Vancouver Landfill  53  Final Closure Strategy  T A B L E 12: RELATIONSHIP B E T W E E N CLASSIFIED SOILS A N D SURFICIAL DEPOSITS - S U R R E Y AND LANGLEY  Morainal  Fluvial Deposits -  Fluvial Deposits -  Fluvial Deposits -  (glacial till)  Glaciofluvial  Deltaic  Floodplain  Local Streams  Deposits  Deposits  Silty or clayey  Sandy  Surrey  Capilano  Embree  Matsqui  Columbia  Kitter  Fairfield  Ross  Lynden  Ladner  Hallert  Westlang  Silty or clayey  Silty or clayey  Annis  Carvolth  McLellan  Hjorth  Nicomekl  Katzie  Sandel  Monroe  Spetifore  Niven  Vinod  Page Prest  T A B L E 12: RELATIONSHIP B E T W E E N CLASSIFIED SOILS A N D SURFICIAL DEPOSITS - S U R R E Y A N D L A N G L E Y (CON'T)  Glaciomarine Deposits  Clayey  Marine  Eolian V e n e e r  Organic  Organic  Deposits  over  Deposits  Deposits  L a g a n d Littoral  Glaciofluvial Deposits  (40-160 c m deep)  (>160  cm deep)  Albion  Berry  Bose  Abbotsford  Banford  Annacis  Nicholson  Cloverdale  Boosey  Coghlan  Gibson  G l e n Valley  Scat  Langley  Heron  Lehman  Goudy  Lumbum  Whatcom  Milner  Livingstone  Judson  Triggs  Murrayville  Lulu  Summer  Richmond  Sunshine  Of the 53 different soils, 21 have grain size and/or Atterberg limit data associated with their classification. This data aids in the assessment of the soil as suitable hydraulic barrier construction material. The soil types, for which data is available are: Abbotsford, Albion, Berry, Bose, Cloverdale, Columbia, Fairfield, Ladner, Langley, Livingstone, Milner, Matsqui, Monroe, Nicholson, Page, Richmond, Scat, Spetifore, Summer, Sunshine and Whatcom. These classified soils will now be discussed individually with respect to suitability as construction material. Abbotsford (AD) Abbotsford soils are described as 20-50 cm of medium textured eolian deposits over gravelly glacial outwash. Two different sets of grain size data exist for soil classified as Abbotsford. One survey was completed in 1972 and the other in 1976. Tables 13 and 14 The Vancouver Landfill  54  Final Closure Strategy  summarize the reported data. The soil at the bottom of the profile, described as sand, gravelly, in Table 13, contains very little clay (< 2 um). As well, coarse fragments including gravel and cobble sized particles comprise 40%. The soil horizons described as silt loam also do not contain very much clay. Only the upper most horizon (Ap) which is 9 cm thick contains sufficient clay to pass soils selection criteria. The survey completed in 1972 (Table 14) does not contain as much data as the 1976 (Table 13) survey, but the same grain size distribution over the soil profile is evident. Overall, soils classified as Abbotsford do not meet soil selection criteria for suitability as hydraulic barrier construction material. T A B L E 13: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S A B B O T S F O R D (1976)  Thickness Horizon Depth (cm)  Coarse Fragments (%) vol gravel cobble  Texture  Particle Size Distribution (%) sand silt (62-2um) clay (2um)  Ap Bf1 Bf2  0-9 9-17  silt loam silt loam  28  67 67  17-29  silt loam  31  66  3  Bm1  29-46  silt loam  36  60  4  Bm2  46-63  silt loam  47  Bm3 IICB  silt loam sand, gravelly  40  35  5  63 81  50 34 17  3 2  IIC1  63-73 73-90 90-124  sand, gravelly  40  35  5  96  2  2  IIC2  124-145  sand, gravelly  40  35  5  96  3  1  22  11 5  3  T A B L E 14: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S A B B O T S F O R D (1972)  Horizon  Thickness Depth (cm)  Lh  3-0  > 5.1 cm < 5.1 cm < 2.5 cm  Particle Size (%) < 5.0 mm < 1.0 mm < 74 um < 50 um < 2 um  Ae  0-3  Bf1  3-23  88.0  58.0  4.0  Bf2  23-46  78.0  58.0  5.0  NBC  45-48  IIC1  48-102  2.8  97.2  75.7  47.7  41.2  12.0  5.0  1.0  IIC2  102-127  20.6  79.4  58.0  33.8  27.9  12.0  5.0  2.0  Albion (AB) Albion soils are moderately fine to fine textured glaciomarine deposits, which occur mainly south and east of Murrayville in Langley. Three field surveys contain grain size data and two of these also report Atterberg Limits. Tables 15-17 summarize the data. For horizons where grain size data is available, the soil is fine grained and passes the 10% clay TT._ i r  T  ine vancouvei j^anuiiii  cc  JJ  n:  i /-ii  cu  ±  rinai closure auaiegy  requirement. Clay values range from a low of 24% (Table 15) to a high of'76% (Table 16). Plasticity index values are reported for four horizons (1972-1 survey, Table 16) and for two horizons in the 1972-2 soil survey (Tablel7). Values range between 21.6-44.1%. Soil selection criteria (Daniel et al., 1995) suggest PI values of between 10-40% indicate acceptable barrier construction material. Most of the PI values for Albion soil fall within the acceptable range. Only one horizon does not. A layer at a depth of 61-102 cm with a clay content of 76% and PI value of 44.1%. PI values higher than the acceptable range suggested by Daniel et al. (1995) can still be used, but with greater care. Overall, areas identified as containing soils classified as Albion should be considered as potential borrow sites. T A B L E 15: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S A L B I O N (1970)  Thickness Horizon Depth (cm) Ap Aegj AB Btg1 Btg2 BC Cg  0-15 15-25 25-40 40-65 65-88 88-112 112-128  Texture  sand  silt loam silt loam silty clay loam silty clay silty clay silty clay silty clay  Particle Size (%) silt (62-2um) clay (2um)  8  68  24  2  47  51  T A B L E 16: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S A L B I O N (1972-1)  Particle Size (%) Thickness Horizon Depth (cm) Ah Aeg AB Btg BC Cg  0-20 20-43 43-61 61-102 102-132 132-157  Atterberg Limits  < 1mm  < 74 um  < 50 um  < 2 um  Plastic Limit  100.0  100.0  99.0  69.0  49.5  79.7  30.2  100.0 100.0 100.0  100.0 100.0 99.0  92.0 98.0 95.0  76.0 42.0 42.0  33.9 25.3 24.9  78.0 53.6 55.2  44.1  Liquid Limit  Plasticity Index  28.3 30.3  T A B L E 17: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S A L B I O N (1972-2)  Particle Size (%) Thickness Horizon Depth (cm) Ap Aeg Btg BC  eg  T L .  me  1 7  0-18 18-43 43-81 81-102 102-132  Atterberg Limits  < 1mm  < 74 um  < 50 um  < 2 um  100.0 100.0 100.0 100.0 100.0  92.9 94.0 98.0 97.0 100.0  88.4 91.2 95.1 94.6 99.7  31.1 41.4 41.7 44.4 44.5  T  vancouvei L.auuim  cr JO  Plastic Limit  Liquid Limit  Plasticity Index  30.4  52.0  21.6  28.5  56.6  28.1  T T  1  /~M  n,  .  Fmal Closure Strategy  Berry (BR) Berry soils are moderately fine to fine textured marine deposits occurring mainly in the vicinity of Langley. Only one survey of soil classified as Berry was conducted. The survey was completed in 1965 at a location in Langley. Grain size data is presented in Table 18. Total clay (< 2 um) ranges from a low of 34% to a high of 65% over a depth of 1.17 meters. Soils classified as Berry meet minimum clay requirements for use as hydraulic barrier construction material. Further testing would be required to determine PI values, however areas identified as containing Berry soils should be considered as potential borrow sites. T A B L E 18: R E P O R T E D D A T A FOR SOILS IDENTIFIED A S B E R R Y  Thickness Depth (cm)  Texture  sand  0-20 20-32  silty clay loam silty clay loam  6 6  60 58  34  Bf Bmgj  32-47  silty clay  3  52  45  Aeg Btg1  47-62  silty clay  1  49  50  62-77  heavy clay  1  39  60  Btg2  77-98 98-117  heavy clay  BC  0 2  35 44  65 54  eg  117-  8  49  43  Horizon Ap  silty clay silty clay  Particle Size silt (62-2um) clay (2um) 36  Bose (BO) Bose soils are described as 30-160 cm of gravelly lag or glacial outwash deposits over moderately coarse textured glacial till and some moderately fine textured glaciomarine deposits. Occupy extensive areas on the uplands, in areas including the Municipality of Surrey. Grain size data (Tables 19 and 20) indicates that soils classified as Bose are too coarse to be used as barrier construction material. Coarse sized particles, including gravel, cobble and stone makeup 30-50% of material in B f l , Bf2, Bm and IIBcl horizons listed in Table 19. As well, clay contents listed in Table 20 are less than the 10% minimum. Although the upper 30-160 cm of Bose soils cannot be used, there is still potential use of underlying glaciomarine deposits where present. The basis for this, is in the identification of clay loam horizon at 100 cm depth in the soil survey completed in 1960. The evaluation of the material would have been made on a site-specific basis, but areas identified as Bose should be considered as potential borrow sites. The Vancouver Landfill  57  Final Closure Strategy  T A B L E 19: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S B O S E (1960)  Thickness Depth (cm)  Horizon  Texture  vol  Coarse Fragments (%) Gravel Cobble Stone  Lh  3-0  Bf1  0-22  sandy loam gravelly  50  20  20  10  Bf2  22-60  sandy loam gravelly  50  20  20  10  Bm  60-85  sand gravelly  50  30  10  10  IIBd  85-100 100-+  loam clay loam  30  20  10  IIBc2  T A B L E 20: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S B O S E (1972)  Horizon  Thickness Depth (cm)  < 50 um  < 2 um  Ap  0-15  100.0  92.4  72.6  61.4  35.0  4.0  Bf1  15-41  100.0  83.7  50.9  39.5  10.0  1.0  Bf2  41-71  Bm1  71-81  95.6  81.8  57.0  44.9  9.0  1.0  Bm2 IIBCI  81-91 91-102  100.0  100.0  94.3  90.7  44.0  5.0  IIBC2  102-127  100.0  100.0  95.2  87.7  44.0  6.0  Particle Size (%) > 5.1 cm < 5.1 cm < 2.5 cm < 5 mm < 1mm  4.4  Cloverdale (CD) Cloverdale soils are moderately fine to fine textured marine deposits. Three soils surveys were conducted, one in 1965 and two in 1972, where grain size data was collected in the classification of Cloverdale soils. Tables 21, 22 and 23 list grain size results and Atterberg Limit data for the three surveys. Clay contents of horizons in the 1965 survey (Table 21) range in value from 28-50%. These values are similar to those found in the 1972 surveys (Table 22 and 23) which show clay contents between 33-52% for respective horizons. Plasticity data is available for all of the horizons listed in Table 22 and for two horizons in Table 23. PI values range between 15.4-37.4%, which are within the acceptable range of 10-40% recommended by Daniel et al. (1995). Overall, based on clay contents and PI values, soil classified as Cloverdale is suitable as barrier construction material. Those areas where this soil is identified should be considered as potential borrow sites.  The Vancouver Landfill  58  Final Closure Strategy  T A B L E 21: R E P O R T E D D A T A FOR SOILS IDENTIFIED A S C L O V E R D A L E (1965)  Horizon  Thickness Depth (cm)  Texture  sand  Particle Size (%) silt (62-2um) clay (2um)  Ap  0-15  silty clay loam  2  64  34  Aeg  15-25  silt loam  2  70  28  AB  25-32  silty clay loam  56  38  Btg1  32-48  silty clay  5 1  50  49  Btg2  48-70 70-92  silty clay silty clay  1  49 49 49  50  BC Cg1  92-120  Cg2  120-  1 1  50 50  T A B L E 22: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S C L O V E R D A L E (1972-1)  Particle Size (%) Thickness Horizon Depth (cm) < 1mm  Atterberg Limits Liquid Plasticity Limit Index  < 74 um  < 50 um  < 2 um  Plastic Limit  Ap  0-30  100.0  98  92  33  42.8  58.2  15.4  Btg  30-61  100.0  97.5  91.0  61-81  100.0  98.5  91  26.6 26.7  64.0 63.1  37.4  BC  43.0 46  Cg1 Cg2  81-102  100.0  99.0  99.0  51.0  62.4  35.5  102-127  100.0  99.0  97.0  52.0  26.9 27.3  59.8  32.5  36.4  T A B L E 23: R E P O R T E D D A T A FOR SOILS IDENTIFIED A S C L O V E R D A L E (1972-2)  Particle Size (%) Thickness Horizon Depth (cm) < 1mm Ap  0-28  Aeg  28-33  Atterberg Limits  < 74 um  < 50 um  < 2 um  100.0  88.3  86.1  34.5  Btg  33-68  100.0  98.7  98.0  42.8  BC  68-102  100.0  97.9  95.1  37.0  eg  102-127  100.0  98.5  94.7  38.4  Plastic Limit  Liquid Limit  Plasticity Index  27.4  57.7  30.3  23.1  47.7  24.6  Columbia (CL) Columbia soils are gravelly glacial outwash deposits occurring in areas south of Langley and in Glen Valley. Tables 24 and 25 summarize grain size data which was collected during two soils surveys, 1967 and 1972 respectively. The soil material and profile contains a substantial amount of coarse fragments (25-80%) which increases with depth (table 1967). This pattern is again evident in the grain size distributions of soil sampled during the 1972 survey. Clay contents are < 3.0%, while percentage of material > 2.5 cm is The Vancouver Landfill  59  Final Closure Strategy  between 65-80%. Based on this information, soils classified as Columbia are not suitable as barrier construction material. T A B L E 24: R E P O R T E D D A T A FOR SOILS IDENTIFIED A S C O L U M B I A (1967)  Horizon  Thickness Depth (cm)  Lh Aej  3-0 0-2  vol  Coarse Fragments (% ) gravel cobble stone  Bf1  2-17  25  Bf2 CB  17-45  55  25  15  15  45-75 75-  80 80  50 50  15 15  15 15  C  T A B L E 25: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S C O L U M B I A (1972)  Thickness Particle Size (%) Horizon Depth (cm) > 5.1 c m < 5.1 cm < 2.5 cm < 5 mm < 1mm < 74 um < 50 um Lh Bf1  3-0 0-15  Bf2  15-46  IIC1 IIC2  102-127  46-102  11.0 18.0  89.0  79.0  57.9  48.0  34.0  82.0  65.0  35.2  28.0  17.0  10.0 5.0  90.0 95.0  68.0 80.0  41.0  33.0 28.0  30.0 26.0  37.6  24.0  < 2 um 1.0 3.0  6.0 6.0  2.0 2.0  Fairfield (F) Fairfield soils are medium to moderately fine textured, laterally accreted floodplain deposits, common on the Fraser River floodplain. Grain size data is available for material sampled during a 1970 soil survey. Table 26 lists the data. Only two of three horizons described as silt loam have accompanying grain size distribution. Clay content for these two horizons, which are at depths of 22-37 cm and 37-57 cm, are 23 and 28% respectively. Textural descriptions of soil below these two horizons are of silty clay loam and fine sandy loam grading into sand. No grain size data exists for these horizons and so comments cannot be made as to the suitability of material. The grain size data that is available however, indicates that the material passes the minimum clay requirement of 10% and has potential for use in the construction of a hydraulic barrier layer. The two horizons meeting requirements, have a total thickness of 30 cm. Site specific testing would be required to determine the suitability of material below these horizons. Areas described as containing Fairfield soils should be viewed with caution but also as potential borrow sites. The Vancouver Landfill  60  Final Closure Strategy  T A B L E 26: R E P O R T E D D A T A FOR SOILS IDENTIFIED A S FAIRFIELD  Horizon  Thickness Depth (cm)  Texture  sand  Ap  0-27  silt loam  Aegj  27-37  silt loam  7  Btjgjl Btjgj2 IIBC  37-57  silt loam  1  57-75  silty clay loam  75-100 100-127  fine sandy loam  "Cg IHCg  127-175  Particle Size (%) silt (62-2um) total clay (2um) 70 71  23 28  fine sandy loam fine sand  Ladner (L) Ladner soils are moderately fine to fine textured deltaic deposits occurring in areas in the Serpentine-Nicomekl Valley. Grain size data and Atterberg Limits are available for material collected during two different soil surveys in 1972. Tables 27 and 28 list the results. Clay contents listed for the first survey are between 19-26% in decrease with depth. PI values for the top three horizons are 14.7,15.7 and 13.4% respectively, while the bottom two horizons have PI values of 8.7 and 9.3%. The trend in clay and PI values is repeated in the second survey with clay contents ranging from 21.3-27% and PI values, for the three horizons tested, 8.4,11.9 and 11.5%. As in the first survey, the bottom horizon has the lowest clay content and a PI value < 10%. Although all clay contents meet E P A soil selection requirements, the use of material with PI values < 10% should be viewed with caution. The reasons for which had been identified previously. Overall, areas classified as containing Ladner soils could be potential borrow sites even though the profile does not indicate "ideal" material. T A B L E 27: R E P O R T E D D A T A FOR SOILS IDENTIFIED A S L A D N E R (1972-1)  Particle Size (%) Horizon  Atterberg Limits  Thickness Depth (cm)  < 1mm  < 74 um  < 50 um  < 2 um  Plastic Limit  Liquid Limit  Plasticity Index  Ap  0-18  100.0  98.0  96.0  25.0  31.8  46.5  14.7  Btg1  18-41  100.0  98.0  98.0  26.0  27.2  42.9  15.7  BC Cg2  41-66 66-102  100.0  94.3  98.0  24.0  25.7  39.1  13.4  85.0  86.0  21.0  26.5  35.2  8.7  Cgs  102-127  91.0  86.0  19.0  31.3  40.6  9.3  The Vancouver Landfill  61  Final Closure Strategy  T A B L E 28: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S L A D N E R (1972-2)  Particle Size (%) Horizon  Thickness Depth (cm)  < 1mm  < 74 um  Atterberg Limits  < 50 um  < 2 um  Ap  0-20  100.0  97.4  93.6  26.1  AB  20-41  100.0  97.7  94.0  25.7  Btg  100.0  97.2 94.7  Cgs  102-140  98.8 94.0 95.6  27.0  eg  41-61 61-102  100.0 100.0  95.3  23.8 21.3  Plastic Limit  Liquid Limit  Plasticity Index  29.0  40.5  11.5  25.3  37.2  33.6  42.0  11.9 8.4  Langley (LA) Langley soils are fine to moderately fine textured marine deposits occurring mainly in the vicinity of Milner (Langley). Two soil surveys, one conducted in 1965 to the other in 1972, contain useful grain size data. For the 1965 (Table 29) survey, soil horizons are described as silt clay or heavy clay. Particles < 2 um vary in abundance with values between 42 and 64%. The remainder of the grain size distribution is dominated by silt (62-2 um), making up 36-54%. For the survey conducted in 1972 (Table 30), grain size data as well as Atterberg Limits were recorded. A l l horizons have 100% of material < 1.0 mm with the clay fraction between 31 -50%. PI values for the upper most and bottom three horizons are between 11 and 43%. The horizon Ahe with a thickness of 12 cm has a PI of 7.4%. The horizons with PI values of 7.4 and 42.8% fall out of the acceptable range of soil criteria. However, the excavation of the entire soil profile as one layer should adequately mix the material to give a soil with a PI value within the acceptable criteria. Overall, the data indicates that soil classified as Langley is suitable for use in the construction of a hydraulic barrier layer. T A B L E 29: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S L A N G L E Y (1965)  Horizon  Thickness Depth (cm)  Texture  sand  Ap  0-22  silty clay  2  45  53  Ah  22-37  silty clay  Aeg  37-47  silty clay  5  53  42  BA  47-57  silty clay  2  54  44  Btg  57-85  heavy clay  1  38  61  BC  85-100 100-127  heavy clay heavy clay  1  38  61  127-  heavy clay  36  64  Cg1 Cg2  -T^l- _  i  IT  .. T  ne v ancouver  Lanumi  62  Particle Size (%) silt (62-2um) clay (2um)  Final Closure Strategy  T A B L E 30: R E P O R T E D D A T A FOR SOILS IDENTIFIED A S L A N G L E Y (1972)  Particle Size (%) Horizon  Thickness Depth (cm)^  Atterberg Limits  < 1mm  < 74 um  < 50 um  < 2 um  Ap  0-18  100.0  97.0  91.1  37.0  Ahe Btg BC  18-30 30-66 66-102  100.0 100.0 100.0  98.0 99.5  98.0 97.0  100.0  97.0  31.0 50.0 48.0  eg  102-127  100.0  99.0  97.0  42.0  Plastic Limit 64.7 56.4  Liquid Limit  Plasticity Index  75.9  11.2 7.4  37.9  63.8 71.7  33.8  26.9  69.7  42.8  22.0  49.7  27.7  Livingstone (LV) Livingstone soils are < 100 cm of moderately coarse textured littoral deposits over fine textured marine deposits. This soil occurs only in the Langley Valley in the vicinities of Langley and Milner. Soil surveys completed in 1965 and 1972 indicate a sand-based material overlying a clay-based material. Table 31 outlines 1965 data. Grain size testing was completed only on material described as silty clay loam and silty clay. These horizons extended from a depth of 50-167 cm and have clay contents ranging from 33-46%. Table 32 outlines 1972 data, which includes Atterberg Limits. As expected, the upper three horizons contain 10.4% or less clay and the single plasticity index value listed is 0.7%. For the bottom two horizons, extending from a depth of 58 cm, clay contents are 45.1 and 54.4%. PI values are also higher at 31.8 and 37.5% and fall within the acceptable range of soil suitability criteria. Assuming the unsuitable sandy material can be excavated independently, areas with soil classified as Livingstone should be considered as potential borrow sites. T A B L E 31: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S L I V I N G S T O N E (1965)  Horizon  Thickness Depth (cm)  Ap Ahe  0-18  loam  18-25  sandy loam  Bfgj  25-37  loamy sand  Bg II Aeg  37-50  loamy sand  50-62  silty clay loam  IIBtgl  62-80  Texture  sand  Particle Size (%) silt (62-2um) clay (2um)  17  50  33  8  49  43  IIBtg2  80-102  silty clay  17  50  33  IIBC  102-125  silty clay  8  49  43  MCg  125-162  silty clay  1  53  46  The Vancouver Landfill  63  Final Closure Strategy  T A B L E 32: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S L I V I N G S T O N E (1972)  Particle Size (%) Horizon  Thickness Depth (cm)  < 1mm  < 74 um  < 50 um  < 2 um  100.0 92.6  75.1 38.8  61.3 44.7  10.4  Ahe  0-20 20-33  Bfgj IIAeg  33-58 58-102  100.0 100.0  23.4 97.9  21.8 94.0  8.1 45.1  HBtg  102-127  100.0  98.5  99.7  54.4  Ap  9.8  Plastic Limit  A tterberg Limits Liquid Plasticity Limit Index  31.3  32.0  0.7  24.4  56.2  31.8  25.1  62.6  37.5  Matsqui (MQ) Matsqui soils are described as 15-50 cm of medium textured, laterally accreted floodplain deposits over sand. Occupying scattered locations on the Fraser River floodplain. A soil survey conducted in 1972 includes grain size distribution and Atterberg limit data. Table 33 outlines the information. The upper most horizon is a fine grained material containing 31% clay and has a PI of 15.2%. Below this, the material becomes coarser with 14% clay and a PI value of 3.4%. The bottom two horizons are dominated by material with particle sizes between 0.074-1.0 mm. Clay contents are less than 2.0% and therefore no plasticity data exists for these horizons. Although the upper most horizon passes soil selection criteria, the soil data indicates that areas identified as Matsqui soils should not be considered as potential borrow sites. T A B L E 33: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S M A T S Q U I (1972)  Particle Size (%) Horizon  Thickness Depth (cm)  < 1mm  < 74 um < 50 um  Atterberg Limits < 2 um  Plastic Limit  Liquid Limit  Plasticity Index  Ap  0-23  100.0  99.5  91.0  31.0  38.6  53.8  15.2  Bm  23-48  100.0  79.0  63.0  14.0  23.7  27.1  3.4  IIC1  48-102  100.0  7.5  9.0  2.0  IIC2  102-127  100.0  7.0  5.0  1.0  Milner (ML) Milner soils are fine to moderately fine textured marine deposits, which occupy substantial areas in the Langley Valley. Grain size and Atterberg limit data from a soil survey conducted in 1972 is listed in Table 34. Data describing horizons extending from 20  The Vancouver Landfill  64  Final Closure Strategy  cm to the depth of 165 cm shows soil that is suitable for use in the construction of a hydraulic barrier layer. Clay contents range in value between 27-39% and PI values are between 15.626.3%. Areas where soils classified as Milner are present should be investigated for potential borrow sites. T A B L E 34: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S M I L N E R (1972)  Particle Size (%) Horizon Bf1 Bf2  Thickness Depth (cm)  < 1mm  < 74 um < 50 um  < 2 um  Plastic Limit  Atterberg Limits Liquid Plasticity Limit Index  0-20 20-38 38-74  100.0  96.0  83.0  27.0  32.6  48.2  15.6  Bm  100.0  98.0  90.0  32.0  32.3  53.2  20.9  Ae BA  74-102  100.0  24.4 23.4  24.0  92.0  34.0 34.0  48.4 46.5  23.1  Bt  140-165  100.0 100.0  99.0 100.0  93.0  102-140  100.0  96.0  39.0  24.0  50.3  26.3  Monroe (M) Monroe soils are medium textured, laterally accreted fioodplain deposits. The largest areas are in Matsqui Valley and on Nicomen Island. Table 35 lists grain size data and Atterberg limit data for samples collected during a 1972 soil survey. The upper two horizons contain 25 and 26% clay, have PI values of 12.6 and 9.8% and extend to a depth of 58 cm. The lower two horizons contain 11.0 and 7.0% clay. The use of soil material originating from areas classified as Monroe must be viewed with caution. Three of four horizons pass a clay requirement of 10% however, PI values are available for only two, one of which is technically outside of the acceptable materials range. T A B L E 35: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S M O N R O E (1972)  Particle Size (%) Horizon  Thickness Depth (cm)  < 1mm  < 74 um < 50 um  Atterberg Limits < 2 um  Plastic Limit  Liquid Limit  Plasticity Index  Ap  0-20  100.0  98.0  95.0  25.0  36  48.6  12.6  Bm  20-58  100.0  99.0  97.0  26.0  33  42.8  9.8  BC  58-97  100.0  76.0  64.0  11.0  C  97-127  100.0  69.5  50.0  7.0  The Vancouver Landfill  65  Final Closure Strategy  Nicholson (N) Nicholson soils are moderately fine textured glaciomarine deposits, occurring in Langley and Surrey municipalities. Two soil surveys have grain size data associated, one conducted in 1970 and other in 1972. Table 36 outlines 1970 data. Not all horizons have grain size data however those that are given, have clay contents between 22-32%. Table 37 outlines 1972 data. The upper horizon, which extends to a depth of 20 cm, has a clay content of 11.1%. Below this is a layer of material with only 7.6% clay and a PI value of 0.5%. Clay content again increases in the next horizon with 14.3% clay. The two lowest horizons (extending to a depth of 127 cm) have 26.2 and 30.7% clay contents respectively. Clay contents for four of five horizons pass the 10% minimum clay requirement. Although Atterberg limit data is unavailable, areas characterized by Nicholson soils should be considered for potential borrow sites. T A B L E 36: R E P O R T E D D A T A FOR SOILS IDENTIFIED A S N I C H O L S O N (1970)  Horizon Ap Bf1 Bf2 IIAe IIAB  Thickness Depth (cm)  Particle Size (%) silt (62-2um) clay (2um)  Texture  sand  10-20  silt loam silt loam  9  69  22  20-30  silt loam 15  55  28  18  50  32  18  50  32  0-10  30-42  silty clay loam  42-52  silty clay loam  IIBtl  52-77  silty clay loam  IIBL2  77-100  silty clay  BC  100-120  silty clay loam  C  120-150  silty clay loam  T A B L E 37: R E P O R T E D D A T A F O R SOILS IDENTIFIED A S N I C H O L S O N (1972)  Particle Size (%) Horizon  Thickness Depth (cm)  < 1mm  < 74 um  < 50 um  Atterberg Limits < 2 um  Plastic Limit  Liquid Limit  Plasticity Index  41.7  42.2  0.5  Ap  0-20  100.0  79.3  77.2  Bfcc  20-36  100.0  84.3  78.1  11.1 7.6  IIAe tl Bt  36-46  100.0  74.5  70.0  14.3  46-102  100.0  82.8  80.0  26.2  MC  102-127  82.3  30.7  The Vancouver Landfill  66  Final Closure Strategy  Page (PE) Page soils are described as medium to moderately fine textured fioodplain deposits, which occupy substantial areas of the Fraser River fioodplain. Data collected during a soil survey in 1967 is listed in Table 38. Clay contents decrease with increasing depth from 25, to 20 to 14% for the upper three horizons with textures of silt loam. Grain size data is unavailable below a depth of 102 cm. A second survey listing grain size data, was conducted in 1972. Results are outlined in Table 39. The upper two soil horizons contain 29.0 and 31.0% clay and have PI values of 31.3 and 15.2% respectively. The third horizon, which extends from a depth of 64 to 89 cm, is composed almost entirely of particle sizes between 0.074 and 1.0 mm. Clay content is only 1.0%. The horizon below this contains a high percentage of clay (26.0%) and has a PI value of 13.6%. The data from the two soil surveys combined, indicates material classified as Page can potentially be used in the construction of a hydraulic barrier layer. T A B L E 38: R E P O R T E D D A T A FOR SOILS IDENTIFIED A S P A G E (1967)  Horizon  Thickness Depth (cm)  Ap Bg Cg1 Cg2 HCg  0-15 15-57 57-102 102-117 117-  Particle Size (%) Texture sand silt (62-2um) clay (2um) silt loam 1 74 25 silt loam 1 79 20 silt loam 11 75 14 silt loam sand  T A B L E 39: R E P O R T E D D A T A FOR SOILS IDENTIFIED A S P A G E (1972)  Particle Size (%) Horizon Ap Bg NCg  eg  Thickness Depth (cm) 0-25 25-64 64-89 89-102  < 1mm < 74 um < 50