Table of Contents
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VOLUME 1. GEOTECHNICAL REPORT
EXECUTIVE SUMMARY PREFACE 1.0 INTRODUCTION 1.1 Purpose 1.2 Scope of Services 1.3 Report Organization 1.4 Authorization 1.5 Limitations
EXECUTIVE SUMMARY
PREFACE
1.0 INTRODUCTION
1.1 Purpose 1.2 Scope of Services 1.3 Report Organization 1.4 Authorization 1.5 Limitations
PART 1. LANDSLIDE INVENTORY AND ANALYSES
2.0 GEOLOGIC CONDITIONS 2.1 Topography 2.2 Stratigraphy 2.2.1 Tertiary Bedrock 2.2.2 Pre-Vashon Deposits 2.2.3 Vashon Glacial Deposits 2.2.4 Holocene Deposits 2.3 Groundwater and Wet Weather 3.0 METHODOLOGY 3.1 Data Sources 3.2 Data Description 3.2.1 Landslide Identification 3.2.2 Landslide Characteristics 3.2.3 Stratigraphy (Geology) 3.2.4 Landslide Trigger Mechanisms 3.2.5 Roads and Public Utility Impact 3.2.6 Damage and Repair (Mitigation) 3.3 Data Processing 4.0 LANDSLIDES 4.1 Landslide Types 4.1.1 High Bluff Peeloff 4.1.2 Groundwater Blowout 4.1.3 Deep-Seated Landslides 4.1.4 Shallow Colluvial (Skin Slide) 4.2 Timing of Landslides 4.3 Landslide Areas 4.4 Causes of Landslides 4.5 Potential Slide and Steep Slope Areas
2.0 GEOLOGIC CONDITIONS
2.1 Topography 2.2 Stratigraphy 2.2.1 Tertiary Bedrock 2.2.2 Pre-Vashon Deposits 2.2.3 Vashon Glacial Deposits 2.2.4 Holocene Deposits 2.3 Groundwater and Wet Weather
2.1 Topography 2.2 Stratigraphy
2.2.1 Tertiary Bedrock 2.2.2 Pre-Vashon Deposits 2.2.3 Vashon Glacial Deposits 2.2.4 Holocene Deposits
2.3 Groundwater and Wet Weather
3.0 METHODOLOGY
3.1 Data Sources 3.2 Data Description 3.2.1 Landslide Identification 3.2.2 Landslide Characteristics 3.2.3 Stratigraphy (Geology) 3.2.4 Landslide Trigger Mechanisms 3.2.5 Roads and Public Utility Impact 3.2.6 Damage and Repair (Mitigation) 3.3 Data Processing
3.1 Data Sources 3.2 Data Description
3.2.1 Landslide Identification 3.2.2 Landslide Characteristics 3.2.3 Stratigraphy (Geology) 3.2.4 Landslide Trigger Mechanisms 3.2.5 Roads and Public Utility Impact 3.2.6 Damage and Repair (Mitigation)
3.3 Data Processing
4.0 LANDSLIDES
4.1 Landslide Types 4.1.1 High Bluff Peeloff 4.1.2 Groundwater Blowout 4.1.3 Deep-Seated Landslides 4.1.4 Shallow Colluvial (Skin Slide) 4.2 Timing of Landslides 4.3 Landslide Areas 4.4 Causes of Landslides 4.5 Potential Slide and Steep Slope Areas
4.1 Landslide Types
4.1.1 High Bluff Peeloff 4.1.2 Groundwater Blowout 4.1.3 Deep-Seated Landslides 4.1.4 Shallow Colluvial (Skin Slide)
4.2 Timing of Landslides 4.3 Landslide Areas 4.4 Causes of Landslides 4.5 Potential Slide and Steep Slope Areas
PART 2. GEOTECHNICAL EVALUATIONS
5.0 PURPOSE AND SCOPE 5.1 Purpose of Geotechnical Evaluations 5.2 Scope of Geotechnical Evaluations 6.0 TYPICAL IMPROVEMENTS RELATED TO LANDSLIDE TYPE 6.1 Geologic Conditions that Contribute to Landsliding and Instability 6.2 Typical Approaches to Improve Stability 6.3 High Bluff Peeloff Landslides 6.4 Groundwater Blowout Landslides 6.5 Deep-Seated Landslides 6.6 Shallow Colluvial Landslides 7.0 DETAILS REGARDING IMPROVEMENTS 7.1 Surface Water Improvements 7.1.1 Tightlines 7.1.2 Surface Water Systems - Maintenance 7.2 Groundwater Improvements 7.2.1 Interceptor Trench Subdrains and Finger Drains 7.2.2 Springhead Drains 7.2.3 Drainage Blankets 7.2.4 Drilled Drains 7.2.5 Other Subsurface Drainage Systems 7.2.6 Monitoring and Maintaining Subsurface Drainage Systems 7.3 Retaining Structures 7.3.1 In Situ Walls 7.3.2 Gravity Walls 7.4 Soil Reinforcement 7.4.1 Reinforced Soil Walls 7.4.2 Soil Nail Walls 7.5 Grading 7.5.1 Drainage Improvements 7.5.2 Decrease Driving Weight 7.5.3 Increase Resisting Weight 7.5.4 Increase Soil Strength 7.5.5 Remove Unstable Soil 7.6 Catchment or Diversion Structures 7.7 Vegetation 8.0 COST ESTIMATE 9.0 CITY UTILITIES AND STREETS 9.1 Streets 9.1.1 Reduce Infiltration 9.1.2 Storm Water Runoff Control 9.1.3 Subsurface Drainage 9.1.4 Structures and Grading Improvements 9.2 Buried Utilities 9.2.1 Subsurface Drainage 9.2.2 Groundwater Controls 9.2.3 Old Buried Utilities 9.2.4 Grading Improvements 9.2.5 Other Considerations
5.0 PURPOSE AND SCOPE
5.1 Purpose of Geotechnical Evaluations 5.2 Scope of Geotechnical Evaluations
6.0 TYPICAL IMPROVEMENTS RELATED TO LANDSLIDE TYPE
6.1 Geologic Conditions that Contribute to Landsliding and Instability 6.2 Typical Approaches to Improve Stability 6.3 High Bluff Peeloff Landslides 6.4 Groundwater Blowout Landslides 6.5 Deep-Seated Landslides 6.6 Shallow Colluvial Landslides
7.0 DETAILS REGARDING IMPROVEMENTS
7.1 Surface Water Improvements 7.1.1 Tightlines 7.1.2 Surface Water Systems - Maintenance 7.2 Groundwater Improvements 7.2.1 Interceptor Trench Subdrains and Finger Drains 7.2.2 Springhead Drains 7.2.3 Drainage Blankets 7.2.4 Drilled Drains 7.2.5 Other Subsurface Drainage Systems 7.2.6 Monitoring and Maintaining Subsurface Drainage Systems 7.3 Retaining Structures 7.3.1 In Situ Walls 7.3.2 Gravity Walls 7.4 Soil Reinforcement 7.4.1 Reinforced Soil Walls 7.4.2 Soil Nail Walls 7.5 Grading 7.5.1 Drainage Improvements 7.5.2 Decrease Driving Weight 7.5.3 Increase Resisting Weight 7.5.4 Increase Soil Strength 7.5.5 Remove Unstable Soil 7.6 Catchment or Diversion Structures 7.7 Vegetation
7.1 Surface Water Improvements
7.1.1 Tightlines 7.1.2 Surface Water Systems - Maintenance
7.2 Groundwater Improvements
7.2.1 Interceptor Trench Subdrains and Finger Drains 7.2.2 Springhead Drains 7.2.3 Drainage Blankets 7.2.4 Drilled Drains 7.2.5 Other Subsurface Drainage Systems 7.2.6 Monitoring and Maintaining Subsurface Drainage Systems
7.3 Retaining Structures
7.3.1 In Situ Walls 7.3.2 Gravity Walls
7.4 Soil Reinforcement
7.4.1 Reinforced Soil Walls 7.4.2 Soil Nail Walls
7.5 Grading
7.5.1 Drainage Improvements 7.5.2 Decrease Driving Weight 7.5.3 Increase Resisting Weight 7.5.4 Increase Soil Strength 7.5.5 Remove Unstable Soil
7.6 Catchment or Diversion Structures 7.7 Vegetation
8.0 COST ESTIMATE 9.0 CITY UTILITIES AND STREETS
9.1 Streets 9.1.1 Reduce Infiltration 9.1.2 Storm Water Runoff Control 9.1.3 Subsurface Drainage 9.1.4 Structures and Grading Improvements 9.2 Buried Utilities 9.2.1 Subsurface Drainage 9.2.2 Groundwater Controls 9.2.3 Old Buried Utilities 9.2.4 Grading Improvements 9.2.5 Other Considerations
9.1 Streets
9.1.1 Reduce Infiltration 9.1.2 Storm Water Runoff Control 9.1.3 Subsurface Drainage 9.1.4 Structures and Grading Improvements
9.2 Buried Utilities
9.2.1 Subsurface Drainage 9.2.2 Groundwater Controls 9.2.3 Old Buried Utilities 9.2.4 Grading Improvements 9.2.5 Other Considerations
PART 3. LANDSLIDES IN THREE STUDY AREAS WEST SEATTLE, MAGNOLIA/QUEEN ANNE, MADRONA
10.0 GENERAL 10.1 Purpose and Scope 10.2 Actions by City 10.3 Actions by Private Property Owners 10.4 Additional Considerations 11.0 WEST SEATTLE 11.1 Site Description 11.2 Soil Stratigraphy 11.3 Groundwater 11.4 Landslide Types 11.4.1 High Bluff Peeloff Landslides 11.4.2 Groundwater Blowout Landslides 11.4.3 Deep-Seated Landslides 11.4.4 Shallow Colluvial Landslides 11.5 Landslides with Debris Flows 11.6 Timing of Landslides 11.7 Severe Storm-Related Landslides 11.8 Potential Slide Areas 11.9 Stability Improvements 11.9.1 23rd Avenue S.W. 11.9.2 Admiral Way 11.9.3 Fairmount Gulch 11.9.4 Harbor Avenue 11.9.5 Alki Avenue 11.9.6 Boyd Place/Chilberg Place 11.9.7 Jacobsen Road 11.9.8 Beach Drive/Atlas Place 11.9.9 47th Avenue S.W. 11.9.10 Seola Beach 12.0 MAGNOLIA/QUEEN ANNE 12.1 Site Description 12.2 Soil Stratigraphy 12.3 Groundwater 12.4 Landslide Types 12.4.1 High Bluff Peeloff 12.4.2 Groundwater Blowout Landslides 12.4.3 Deep-Seated Landslides 12.4.4 Shallow Colluvial Landslides 12.5 Landslides with Debris Flows 12.6 Timing of Landslides 12.7 Severe Storm-Related Landslides 12.8 Potential Slide Areas 12.9 Stability Improvements 12.9.1 Perkins Lane North 12.9.2 Perkins Lane South 12.9.3 32nd Avenue W. 12.9.4 W. Galer Street 12.9.5 Magnolia Way 12.9.6 Kinnear Park 12.9.7 West Queen Anne 12.9.8 Northwest Queen Anne 12.9.9 East Queen Anne 13.0 MADRONA 13.1 Site Description 13.2 Soil Stratigraphy 13.3 Groundwater 13.4 Landslide Types 13.4.1 High Bluff Peeloff Landslides 13.4.2 Groundwater Blowout Landslides 13.4.3 Deep-Seated Landslides 13.4.4 Shallow Colluvial Landslides 13.5 Landslides with Debris Flows 13.6 Timing of Landslides 13.7 Severe Storm-Related Landslides 13.8 Potential Slide Areas 13.9 Stability Improvements 13.9.1 Hillside Drive 13.9.2 32nd Avenue E. 13.9.3 Madrona Drive 13.9.4 Madrona Park 13.9.5 Lake Dell 13.9.6 Lakeside North 13.9.7 Lakeside South
10.0 GENERAL
10.1 Purpose and Scope 10.2 Actions by City 10.3 Actions by Private Property Owners 10.4 Additional Considerations
11.0 WEST SEATTLE
11.1 Site Description 11.2 Soil Stratigraphy 11.3 Groundwater 11.4 Landslide Types 11.4.1 High Bluff Peeloff Landslides 11.4.2 Groundwater Blowout Landslides 11.4.3 Deep-Seated Landslides 11.4.4 Shallow Colluvial Landslides 11.5 Landslides with Debris Flows 11.6 Timing of Landslides 11.7 Severe Storm-Related Landslides 11.8 Potential Slide Areas 11.9 Stability Improvements 11.9.1 23rd Avenue S.W. 11.9.2 Admiral Way 11.9.3 Fairmount Gulch 11.9.4 Harbor Avenue 11.9.5 Alki Avenue 11.9.6 Boyd Place/Chilberg Place 11.9.7 Jacobsen Road 11.9.8 Beach Drive/Atlas Place 11.9.9 47th Avenue S.W. 11.9.10 Seola Beach
11.1 Site Description 11.2 Soil Stratigraphy 11.3 Groundwater 11.4 Landslide Types
11.4.1 High Bluff Peeloff Landslides 11.4.2 Groundwater Blowout Landslides 11.4.3 Deep-Seated Landslides 11.4.4 Shallow Colluvial Landslides
11.5 Landslides with Debris Flows 11.6 Timing of Landslides 11.7 Severe Storm-Related Landslides 11.8 Potential Slide Areas 11.9 Stability Improvements
11.9.1 23rd Avenue S.W. 11.9.2 Admiral Way 11.9.3 Fairmount Gulch 11.9.4 Harbor Avenue 11.9.5 Alki Avenue 11.9.6 Boyd Place/Chilberg Place 11.9.7 Jacobsen Road 11.9.8 Beach Drive/Atlas Place 11.9.9 47th Avenue S.W. 11.9.10 Seola Beach
12.0 MAGNOLIA/QUEEN ANNE
12.1 Site Description 12.2 Soil Stratigraphy 12.3 Groundwater 12.4 Landslide Types 12.4.1 High Bluff Peeloff 12.4.2 Groundwater Blowout Landslides 12.4.3 Deep-Seated Landslides 12.4.4 Shallow Colluvial Landslides 12.5 Landslides with Debris Flows 12.6 Timing of Landslides 12.7 Severe Storm-Related Landslides 12.8 Potential Slide Areas 12.9 Stability Improvements 12.9.1 Perkins Lane North 12.9.2 Perkins Lane South 12.9.3 32nd Avenue W. 12.9.4 W. Galer Street 12.9.5 Magnolia Way 12.9.6 Kinnear Park 12.9.7 West Queen Anne 12.9.8 Northwest Queen Anne 12.9.9 East Queen Anne
12.1 Site Description 12.2 Soil Stratigraphy 12.3 Groundwater 12.4 Landslide Types
12.4.1 High Bluff Peeloff 12.4.2 Groundwater Blowout Landslides 12.4.3 Deep-Seated Landslides 12.4.4 Shallow Colluvial Landslides
12.5 Landslides with Debris Flows 12.6 Timing of Landslides 12.7 Severe Storm-Related Landslides 12.8 Potential Slide Areas 12.9 Stability Improvements
12.9.1 Perkins Lane North 12.9.2 Perkins Lane South 12.9.3 32nd Avenue W. 12.9.4 W. Galer Street 12.9.5 Magnolia Way 12.9.6 Kinnear Park 12.9.7 West Queen Anne 12.9.8 Northwest Queen Anne 12.9.9 East Queen Anne
13.0 MADRONA
13.1 Site Description 13.2 Soil Stratigraphy 13.3 Groundwater 13.4 Landslide Types 13.4.1 High Bluff Peeloff Landslides 13.4.2 Groundwater Blowout Landslides 13.4.3 Deep-Seated Landslides 13.4.4 Shallow Colluvial Landslides 13.5 Landslides with Debris Flows 13.6 Timing of Landslides 13.7 Severe Storm-Related Landslides 13.8 Potential Slide Areas 13.9 Stability Improvements 13.9.1 Hillside Drive 13.9.2 32nd Avenue E. 13.9.3 Madrona Drive 13.9.4 Madrona Park 13.9.5 Lake Dell 13.9.6 Lakeside North 13.9.7 Lakeside South
13.1 Site Description 13.2 Soil Stratigraphy 13.3 Groundwater 13.4 Landslide Types
13.4.1 High Bluff Peeloff Landslides 13.4.2 Groundwater Blowout Landslides 13.4.3 Deep-Seated Landslides 13.4.4 Shallow Colluvial Landslides
13.5 Landslides with Debris Flows 13.6 Timing of Landslides 13.7 Severe Storm-Related Landslides 13.8 Potential Slide Areas 13.9 Stability Improvements
13.9.1 Hillside Drive 13.9.2 32nd Avenue E. 13.9.3 Madrona Drive 13.9.4 Madrona Park 13.9.5 Lake Dell 13.9.6 Lakeside North 13.9.7 Lakeside South
PART 4. LANDSLIDES IN NORTH, CENTRAL, AND SOUTH SEATTLE
14.0 GENERAL 14.1 Purpose and Scope 14.2 Actions by City 14.3 Actions by Private Property Owners 15.0 NORTHWEST SEATTLE 15.1 Site Description 15.2 Stability Improvements 15.3 Broadview 15.4 25th Avenue N.W. 15.5 Carkeek Park 15.6 Blue Ridge 15.7 Golden Gardens 15.8 Shilshole 16.0 NORTHEAST SEATTLE 16.1 Site Description 16.2 Stability Improvements 16.3 Burke Gilman 16.4 Inverness 16.5 Laurelhurst 17.0 CAPITOL HILL 17.1 Site Description 17.2 Stability Improvements 17.3 North Capitol Hill 17.4 Interlaken 17.5 West Capitol Hill 18.0 SOUTH SEATTLE 18.1 Site Description 18.2 Stability Improvements 18.3 Mount Baker 18.4 25th Avenue S. 18.5 West Beacon Hill 18.6 Duwamish 18.7 Rainier Beach
14.0 GENERAL
14.1 Purpose and Scope 14.2 Actions by City 14.3 Actions by Private Property Owners
15.0 NORTHWEST SEATTLE
15.1 Site Description 15.2 Stability Improvements 15.3 Broadview 15.4 25th Avenue N.W. 15.5 Carkeek Park 15.6 Blue Ridge 15.7 Golden Gardens 15.8 Shilshole
16.0 NORTHEAST SEATTLE
16.1 Site Description 16.2 Stability Improvements 16.3 Burke Gilman 16.4 Inverness 16.5 Laurelhurst
17.0 CAPITOL HILL
17.1 Site Description 17.2 Stability Improvements 17.3 North Capitol Hill 17.4 Interlaken 17.5 West Capitol Hill
18.0 SOUTH SEATTLE
18.1 Site Description 18.2 Stability Improvements 18.3 Mount Baker 18.4 25th Avenue S. 18.5 West Beacon Hill 18.6 Duwamish 18.7 Rainier Beach
PART 5. POTENTIAL SLIDE AREAS
19.0 PURPOSE AND SCOPE 20.0 BACKGROUND 21.0 RESULTS 22.0 REFERENCES
LIST OF TABLES
PART 2 2-1 Typical Improvement Unit Costs (4 pages) PART 3 3-1 Stability Improvement Areas, West Seattle, Magnolia/Queen Anne, Madrona PART 4 4-1 Stability Improvement Areas, Northwest, Northeast, Capitol Hill, South Seattle
2-1 Typical Improvement Unit Costs (4 pages)
PART 3
3-1 Stability Improvement Areas, West Seattle, Magnolia/Queen Anne, Madrona
PART 4
4-1 Stability Improvement Areas, Northwest, Northeast, Capitol Hill, South Seattle
LIST OF FIGURES
Figure No. PART 1 1-1 Idealized Geologic Conditions, Typical Seattle Hillside 1-2 High Bluff Peeloff Landslide Type 1-3 Groundwater Blowout Landslide Type 1-4 Deep-Seated Landslide Type 1-5 Shallow Colluvial (Skin Slide) Landslide Type 1-6 Landslide in Fill Material 1-7 Annual Distribution of Landslides 1-8 Monthly Distribution of Landslides (sheet 1 sheet 2) 1-9 Human Influence on Landslides 1-10 Types of Landslides PART 2 2-1 Typical High Bluff Peeloff Landslide Stability Improvements (sheet 1 sheet 2 sheet 3) 2-2 Typical Groundwater Blowout Landslide Stability Improvements (sheet 1 sheet 2) 2-3 Typical Deep-Seated Landslide StabilityImprovements (sheet 1 sheet 2 sheet 3) 2-4 Typical Shallow Colluvial Landslide Stability Improvements (sheet 1 sheet 2) 2-5 Typical Landslide in Fill Material Stability Improvements 2-6 Typical Tightline Anchoring Detail (sheet 1 sheet 2) 2-7 Typical Trench Subdrain Interceptor Trench and Finger Drain (sheet 1 sheet 2) 2-8 Typical Drainage Dam Detail 2-9 Typical Springhead Drain Detail 2-10 Typical Drainage Blanket Detail 2-11 Typical Horizontal, Directional and Vertical Drain Sketch 2-12 Typical Soldier Pile Wall, Design Criteria (sheet 1) 2-12 Typical Soldier Pile Wall, Backfill and Drainage (sheet 2 sheet 3) 2-13 Typical Crib Wall with Subdrainage and Backfilling 2-14 Typical Section, Ecology Block Wall 2-15 Typical Geotextile Soil Wall Section 2-16 Typical Geogrid Reinforced Soil Wall Section 2-17 Typical Section Geotextile-Reinforced Slope 2-18 Typical Fill Buttress 2-19 Typical Soldier Pile Catchment Wall PART 3 3-1 Idealized Geologic Conditions, Duwamish Head Area 3-2 Idealized Geologic Conditions, West Magnolia Bluff
Figure No.
PART 1
1-1 Idealized Geologic Conditions, Typical Seattle Hillside 1-2 High Bluff Peeloff Landslide Type 1-3 Groundwater Blowout Landslide Type 1-4 Deep-Seated Landslide Type 1-5 Shallow Colluvial (Skin Slide) Landslide Type 1-6 Landslide in Fill Material 1-7 Annual Distribution of Landslides 1-8 Monthly Distribution of Landslides (sheet 1 sheet 2) 1-9 Human Influence on Landslides 1-10 Types of Landslides
PART 2
2-1 Typical High Bluff Peeloff Landslide Stability Improvements (sheet 1 sheet 2 sheet 3) 2-2 Typical Groundwater Blowout Landslide Stability Improvements (sheet 1 sheet 2) 2-3 Typical Deep-Seated Landslide StabilityImprovements (sheet 1 sheet 2 sheet 3) 2-4 Typical Shallow Colluvial Landslide Stability Improvements (sheet 1 sheet 2) 2-5 Typical Landslide in Fill Material Stability Improvements 2-6 Typical Tightline Anchoring Detail (sheet 1 sheet 2) 2-7 Typical Trench Subdrain Interceptor Trench and Finger Drain (sheet 1 sheet 2) 2-8 Typical Drainage Dam Detail 2-9 Typical Springhead Drain Detail 2-10 Typical Drainage Blanket Detail 2-11 Typical Horizontal, Directional and Vertical Drain Sketch 2-12 Typical Soldier Pile Wall, Design Criteria (sheet 1) 2-12 Typical Soldier Pile Wall, Backfill and Drainage (sheet 2 sheet 3) 2-13 Typical Crib Wall with Subdrainage and Backfilling 2-14 Typical Section, Ecology Block Wall 2-15 Typical Geotextile Soil Wall Section 2-16 Typical Geogrid Reinforced Soil Wall Section 2-17 Typical Section Geotextile-Reinforced Slope 2-18 Typical Fill Buttress 2-19 Typical Soldier Pile Catchment Wall
3-1 Idealized Geologic Conditions, Duwamish Head Area 3-2 Idealized Geologic Conditions, West Magnolia Bluff
VOLUME 2. MAP FOLIO AND LANDSLIDE DATABASE
LIST OF APPENDICES
APPENDIX A MAP FOLIO - CITYWIDE MAPS Figures A-1 Shaded Relief Map of Seattle A-2 Map Legend A-3 Site Plan of Seattle A-4 Zone of Particular Landslide Hazard A-5 Landslides by Decade A-6 Storm-Related Landslides A-7 Landslide Types A-8 Totally Natural Landslides A-9 High Bluff Peeloff Landslides A-10 Groundwater Blowout Landslides A-11 Deep-Seated Landslides A-12 Shallow Colluvial Landslides A-13 Landslides and Potential Slide Areas A-14 Landslides and Steep Slope Areas A-15 Debris Flow Landslides APPENDIX B MAP FOLIO - STUDY AREA MAPS, WEST SEATTLE, MAGNOLIA/QUEEN ANNE, MADRONA Figures West Seattle B-1 Site Plan B-2 Groundwater Blowout Landslides B-3 Deep-Seated Landslides B-4 Shallow Colluvial Landslides B-5 Debris Flow Landslides B-6 Landslides by Decade B-7 Storm-Related Landslides B-8 Landslides and Potential Slide Areas B-9 Stability Improvement Areas Magnolia/Queen Anne B-10 Site Plan B-11 High Bluff Peeloff Landslides B-12 Groundwater Blowout Landslides B-13 Deep-Seated Landslides B-14 Shallow Colluvial Landslides B-15 Debris Flow Landslides B-16 Landslides by Decade B-18 Landslides and Potential Slide Areas Madrona B-20 Site Plan B-21 Groundwater Blowout Landslides B-22 Deep-Seated Landslides B-23 Shallow Colluvial Landslides B-24 Debris Flow Landslides B-25 Landslides by Decade B-26 Storm-Related Landslides B-27 Landslides and Potential Slide Areas B-28 Stability Improvement Areas APPENDIX C MAP FOLIO - NORTH, CENTRAL, AND SOUTH SEATTLE Figures C-1 Site Plan of Seattle C-2 Northwest Seattle Vicinity Map C-3 Northwest Seattle Stability Improvement Areas C-4 Northeast Seattle Vicinity Map C-5 Northeast Seattle Stability Improvement Areas C-6 Capitol Hill Vicinity Map C-7 Capitol Hill Stability Improvement Areas C-8 South Seattle Vicinity Map C-9 South Seattle Stability Improvement Areas APPENDIX D MAP FOLIO - POTENTIAL SLIDE AREAS Figures D-1 Existing Delineation of Potential Slide Areas D-2 Proposed Delineation of Potential Slide Areas D-3 Losses and Gains of Regulated Land due to Proposed Revisions of Potential Slide Areas APPENDIX E SEATTLE LANDSLIDE DATABASE Seattle Landslide Database
APPENDIX A MAP FOLIO - CITYWIDE MAPS
Figures
A-1 Shaded Relief Map of Seattle A-2 Map Legend A-3 Site Plan of Seattle A-4 Zone of Particular Landslide Hazard A-5 Landslides by Decade A-6 Storm-Related Landslides A-7 Landslide Types A-8 Totally Natural Landslides A-9 High Bluff Peeloff Landslides A-10 Groundwater Blowout Landslides A-11 Deep-Seated Landslides A-12 Shallow Colluvial Landslides A-13 Landslides and Potential Slide Areas A-14 Landslides and Steep Slope Areas A-15 Debris Flow Landslides
APPENDIX B MAP FOLIO - STUDY AREA MAPS, WEST SEATTLE, MAGNOLIA/QUEEN ANNE, MADRONA
West Seattle B-1 Site Plan B-2 Groundwater Blowout Landslides B-3 Deep-Seated Landslides B-4 Shallow Colluvial Landslides B-5 Debris Flow Landslides B-6 Landslides by Decade B-7 Storm-Related Landslides B-8 Landslides and Potential Slide Areas B-9 Stability Improvement Areas Magnolia/Queen Anne B-10 Site Plan B-11 High Bluff Peeloff Landslides B-12 Groundwater Blowout Landslides B-13 Deep-Seated Landslides B-14 Shallow Colluvial Landslides B-15 Debris Flow Landslides B-16 Landslides by Decade B-18 Landslides and Potential Slide Areas Madrona B-20 Site Plan B-21 Groundwater Blowout Landslides B-22 Deep-Seated Landslides B-23 Shallow Colluvial Landslides B-24 Debris Flow Landslides B-25 Landslides by Decade B-26 Storm-Related Landslides B-27 Landslides and Potential Slide Areas B-28 Stability Improvement Areas
B-1 Site Plan B-2 Groundwater Blowout Landslides B-3 Deep-Seated Landslides B-4 Shallow Colluvial Landslides B-5 Debris Flow Landslides B-6 Landslides by Decade B-7 Storm-Related Landslides B-8 Landslides and Potential Slide Areas B-9 Stability Improvement Areas
B-10 Site Plan B-11 High Bluff Peeloff Landslides B-12 Groundwater Blowout Landslides B-13 Deep-Seated Landslides B-14 Shallow Colluvial Landslides B-15 Debris Flow Landslides B-16 Landslides by Decade B-18 Landslides and Potential Slide Areas
B-20 Site Plan B-21 Groundwater Blowout Landslides B-22 Deep-Seated Landslides B-23 Shallow Colluvial Landslides B-24 Debris Flow Landslides B-25 Landslides by Decade B-26 Storm-Related Landslides B-27 Landslides and Potential Slide Areas B-28 Stability Improvement Areas
APPENDIX C MAP FOLIO - NORTH, CENTRAL, AND SOUTH SEATTLE
C-1 Site Plan of Seattle C-2 Northwest Seattle Vicinity Map C-3 Northwest Seattle Stability Improvement Areas C-4 Northeast Seattle Vicinity Map C-5 Northeast Seattle Stability Improvement Areas C-6 Capitol Hill Vicinity Map C-7 Capitol Hill Stability Improvement Areas C-8 South Seattle Vicinity Map C-9 South Seattle Stability Improvement Areas
APPENDIX D MAP FOLIO - POTENTIAL SLIDE AREAS
D-1 Existing Delineation of Potential Slide Areas D-2 Proposed Delineation of Potential Slide Areas D-3 Losses and Gains of Regulated Land due to Proposed Revisions of Potential Slide Areas
APPENDIX E SEATTLE LANDSLIDE DATABASE
Seattle Landslide Database