Contents

Chapter 1 Design Policy............................................................................................. 1-1

1-1 Introduction.................................................................................................................................. 1-1
1-2 Responsibility ............................................................................................................................... 1-1
1-3 Hydraulic Reports....................................................................................................................... 1-3
1-3.1 Hydraulic Report Types......................................................................................... 1-4
1-3.2 Preparing Hydraulic Documentation................................................................ 1-7
1-3.3 Hydraulic Report Deliverables, Submittals, and Archiving....................... 1-9
1-3.4 Developers and Utility Agreements............................................................... 1-16
1-3.5 Upstream and Downstream Analysis ............................................................ 1-16
1-3.6 Existing Stormwater Drainage Conveyance System................................ 1-19
1-4 Storm Frequency Policy and Design Tools and Software ........................................ 1-19
1-5 Complete Streets..................................................................................................................... 1-20
1-6 Hydraulic Design Schedule .................................................................................................. 1-20
1-6.1 Milestones and Scheduling................................................................................ 1-21

Chapter 2 Hydrology.................................................................................................. 2-1

2-1 Introduction.................................................................................................................................. 2-1
2-2 Selecting a Method.................................................................................................................... 2-2
2-3 Drainage Basin............................................................................................................................. 2-5
2-4 Site Basins ..................................................................................................................................... 2-5
2-5 Cold Climate Considerations.................................................................................................. 2-5
2-5.1 Calculating Snowmelt............................................................................................. 2-6
2-5.2 Additional Considerations .................................................................................... 2-6
2-6 Rational Method ......................................................................................................................... 2-7
2-6.1 General......................................................................................................................... 2-7
2-6.2 Runoff Coefficients................................................................................................. 2-8
2-6.3 Time of Concentration........................................................................................... 2-9
2-6.4 Rainfall Intensity.................................................................................................... 2-11
2-7 Single-Event Hydrograph Method: Santa Barbara Urban Hydrograph............... 2-14
2-7.1 Design Storm Hyetograph................................................................................. 2-14
2-7.2 Runoff Parameters ............................................................................................... 2-15
2-8 Continuous-Simulation Hydrologic Model (Western Washington Only)........... 2-18
2-8.1 Modeling Requirements ..................................................................................... 2-19
2-9 Published Flow Records........................................................................................................ 2-22
2-10 USGS Regression Equations................................................................................................ 2-23

WSDOT Hydraulics Manual M 23-03.11 Page i

April 2025
Contents

2-11 Existing Hydrologic Studies ................................................................................................. 2-24

2-12 Examples..................................................................................................................................... 2-24
2-13 Appendices................................................................................................................................. 2-25

Chapter 3 Culvert Design........................................................................................... 3-1

3-1 Introduction.................................................................................................................................. 3-1
3-2 Culvert Design Documentation............................................................................................. 3-1
3-2.1 Hydraulic Design Reports..................................................................................... 3-1
3-2.2 Required Field Data ................................................................................................ 3-2
3-2.3 Engineering Analysis............................................................................................... 3-3
3-3 Hydraulic Design of Culverts ................................................................................................. 3-4
3-3.1 Culvert Design Considerations........................................................................... 3-5
3-3.2 Allowable Headwater............................................................................................. 3-7
3-3.3 Tailwater Conditions............................................................................................ 3-10
3-3.4 Flow Type ................................................................................................................ 3-11
3-3.5 Velocities in Culverts: General......................................................................... 3-11
3-3.6 Culvert Hydraulic Calculations Form............................................................. 3-12
3-3.7 Computer Programs............................................................................................. 3-12
3-3.8 Example .................................................................................................................... 3-12
3-4 Culvert End Treatments........................................................................................................ 3-12
3-4.1 Projecting Ends...................................................................................................... 3-13
3-4.2 Mitered End Sections.......................................................................................... 3-13
3-4.3 Flared End Sections.............................................................................................. 3-14
3-4.4 Headwalls................................................................................................................. 3-15
3-4.5 Wing Walls and Aprons...................................................................................... 3-15
3-4.6 Improved Inlets...................................................................................................... 3-16
3-4.7 Energy Dissipators................................................................................................ 3-17
3-4.8 Culvert Debris ........................................................................................................ 3-18
3-5 Miscellaneous Culvert Design Considerations............................................................. 3-18
3-5.1 Multiple Culvert Openings ................................................................................ 3-18
3-5.2 Camber...................................................................................................................... 3-19
3-5.3 Horizontal and Vertical Angle Points ............................................................ 3-19
3-5.4 Upstream Ponding................................................................................................ 3-20
3-5.5 Miscellaneous Design Considerations: Siphons ........................................ 3-20

Chapter 4 Channels and Floodplains......................................................................... 4-1

4-1 Introduction.................................................................................................................................. 4-1
4-2 Uniform Flow Calculations...................................................................................................... 4-1

WSDOT Hydraulics Manual M 23-03.11 Page ii

April 2025
Contents

4-3 Field Slope Measurements...................................................................................................... 4-2

4-3.1 Uniform Flow Conditions: Gravity Stormwater Systems, Roadside
Ditches and Swales, Roadway Gutters, Streams, and Conveyance
Channels...................................................................................................................... 4-4
4-3.2 Non-Uniform Flow Conditions: Streams and Rivers................................... 4-5
4-3.3 Energy Grade Line ................................................................................................... 4-6
4-4 Critical Depth............................................................................................................................... 4-6
4-5 Manning’s Roughness Coefficients (n)................................................................................ 4-7
4-6 Countermeasures for Stream Instability ............................................................................ 4-8
4-6.1 Bank Protection........................................................................................................ 4-8
4-6.2 Rock for Bank Protection...................................................................................... 4-8
4-6.3 Channel Stabilization ........................................................................................... 4-10
4-7 Flood Risk Assessment.......................................................................................................... 4-11
4-7.1 No-Rise Analysis.................................................................................................... 4-12
4-7.2 Floodplain Analysis............................................................................................... 4-12
4-7.3 Conditional Letter of Map Revision ............................................................... 4-12
4-7.4 Letter of Map Revision ....................................................................................... 4-12
4-8 Hydraulic Analysis for Riverine and Coastal Areas..................................................... 4-13
4-8.1 Intermediate Conditions..................................................................................... 4-13
4-8.2 Tidal Crossings ....................................................................................................... 4-13

Chapter 5 Drainage of Highway Pavements............................................................. 5-1

5-1 Introduction.................................................................................................................................. 5-1
5-2 Hydrology...................................................................................................................................... 5-2
5-3 Highway Drainage...................................................................................................................... 5-2
5-3.1 Bridge Deck and Downstream End Drainage................................................ 5-2
5-3.2 Slotted Drains and Trench Systems.................................................................. 5-3
5-3.3 Drop Inlets.................................................................................................................. 5-3
5-4 Gutter Flow and Inlet Spacing ............................................................................................... 5-3
5-4.1 Capacity of Inlets on a Continuous Grade...................................................... 5-5
5-4.2 Capacity of Inlets at Sag Locations ................................................................... 5-6
5-5 Roadside Ditch Design Criteria ............................................................................................. 5-9
5-6 Drainage Structures................................................................................................................ 5-10
5-6.1 Inlet Structure Types ........................................................................................... 5-10
5-6.2 Grate Types............................................................................................................. 5-13
5-7 Scupper Barrier......................................................................................................................... 5-18
5-8 Hydroplaning and Hydrodynamic Drag........................................................................... 5-19

WSDOT Hydraulics Manual M 23-03.11 Page iii

April 2025
Contents

Chapter 6 Storm Sewer, Drain Pipe, Underdrain Pipe ............................................. 6-1

6-1 Introduction.................................................................................................................................. 6-1
6-2 Storm Sewer ................................................................................................................................. 6-1
6-2.1 Storm Sewer Design Criteria ............................................................................... 6-3
6-2.2 Storm Sewer Data for Hydraulic Reports....................................................... 6-6
6-2.3 Storm Sewer Design: Manual Calculations .................................................... 6-6
6-2.4 Storm Sewer Design: Computer Analysis ....................................................... 6-6
6-2.5 Storm Sewer Hydraulic Grade Line Analysis ................................................. 6-6
6-3 Drain Pipe...................................................................................................................................... 6-8
6-4 Underdrain Pipe .......................................................................................................................... 6-8
6-5 Drywells ......................................................................................................................................... 6-9
6-6 Pipe Materials for Storm Sewers, Drain Pipe, and Underdrain Pipe ....................... 6-9

Chapter 7 Water Crossings........................................................................................ 7-1

7-1 Introduction.................................................................................................................................. 7-1
7-2 Existing Conditions .................................................................................................................... 7-3
7-2.1 Watershed and Land Cover ................................................................................. 7-5
7-2.2 Geology and Soils..................................................................................................... 7-5
7-2.3 Fluvial Geomorphology.......................................................................................... 7-5
7-2.4 Hydrology ................................................................................................................ 7-19
7-2.5 Reference Reach ................................................................................................... 7-20
7-2.6 Bankfull Width....................................................................................................... 7-23
7-3 Design .......................................................................................................................................... 7-23
7-3.1 Determining Crossing Design Methodology for Documentation....... 7-24
7-3.2 Constraints .............................................................................................................. 7-25
7-3.3 Channel Alignment............................................................................................... 7-26
7-3.4 Channel Cross Section ........................................................................................ 7-26
7-3.5 Hydraulic Opening................................................................................................ 7-27
7-3.6 Vertical Clearance................................................................................................. 7-33
7-3.7 Buried Structures.................................................................................................. 7-35
7-3.8 Sediment Design ................................................................................................... 7-36
7-3.9 Channel Complexity............................................................................................. 7-40
7-3.10 Landscaping/Planting .......................................................................................... 7-57
7-4 Scour............................................................................................................................................. 7-57
7-4.1 Total Scour .............................................................................................................. 7-57
7-4.2 Lateral Migration for Water-Crossing Structures..................................... 7-58
7-4.3 Scour Countermeasures..................................................................................... 7-60

WSDOT Hydraulics Manual M 23-03.11 Page iv

April 2025
Contents

7-5 Other Design Methods.......................................................................................................... 7-62

7-5.1 No-Slope Design ................................................................................................... 7-63
7-5.2 Fish Passage Improvement Structures.......................................................... 7-63
7-5.3 Tidal Crossing Structures ................................................................................... 7-63
7-6 Structure-Free Zone............................................................................................................... 7-65
7-6.1 Complete Streets and Effect on Structure-Free Zone............................ 7-65
7-7 Temporary Stream Diversions ............................................................................................ 7-65
7-8 Monitoring.................................................................................................................................. 7-65
7-8.1 Streambed Camera Monitoring ....................................................................... 7-66
7-9 Performance Management .................................................................................................. 7-67
7-10 Additional Resources.............................................................................................................. 7-68
7-11 Appendices................................................................................................................................. 7-69

Chapter 8 Pipe Classifications and Materials............................................................ 8-1

8-1 Introduction.................................................................................................................................. 8-1
8-2 Pipe Classifications .................................................................................................................... 8-2
8-2.1 Drain Pipe ................................................................................................................... 8-2
8-2.2 Underdrain Pipe........................................................................................................ 8-2
8-2.3 Culvert Pipe................................................................................................................ 8-2
8-2.4 Storm Sewer Pipe .................................................................................................... 8-7
8-2.5 Sanitary Sewer Pipe ................................................................................................ 8-8
8-3 Pipe Materials .............................................................................................................................. 8-8
8-3.1 Concrete Pipe............................................................................................................ 8-9
8-3.2 Metal Pipe: General.............................................................................................. 8-10
8-3.3 Thermoplastic Pipe: General............................................................................. 8-13
8-4 Pipe Corrosion Zones and Pipe Alternative Selection............................................... 8-16
8-4.1 Corrosion Zone I.................................................................................................... 8-16
8-4.2 Corrosion Zone II .................................................................................................. 8-17
8-4.3 Corrosion Zone III................................................................................................. 8-17
8-5 Corrosion .................................................................................................................................... 8-24
8-5.1 pH ............................................................................................................................... 8-24
8-5.2 Resistivity................................................................................................................. 8-25
8-5.3 Corrosion Control Methods.............................................................................. 8-25
8-6 Abrasion...................................................................................................................................... 8-26
8-7 Pipe Joints .................................................................................................................................. 8-27
8-8 Pipe Anchors ............................................................................................................................. 8-28
8-8.1 Thrust Blocks.......................................................................................................... 8-28

WSDOT Hydraulics Manual M 23-03.11 Page v

April 2025
Contents

8-9 Pipe Rehabilitation: Trenchless Technology.................................................................. 8-28

8-9.1 Trenchless Techniques for Pipe Rehabilitation.......................................... 8-30
8-10 Pipe Design ................................................................................................................................ 8-33
8-10.1 Categories of Structural Materials: Rigid or Flexible ............................... 8-33
8-10.2 Structural Behavior of Flexible Pipes ............................................................ 8-33
8-10.3 Structural Behavior of Rigid Pipes.................................................................. 8-34
8-10.4 Foundations, Bedding, and Backfill ................................................................ 8-35
8-11 Abandoned Pipe Guidelines ................................................................................................ 8-36
8-12 Structural Analysis and Fill Height Tables ...................................................................... 8-38
8-12.1 Pipe Cover ............................................................................................................... 8-39
8-12.2 Shallow Cover Installation................................................................................. 8-39
8-12.3 Fill Height Tables .................................................................................................. 8-40

Chapter 9 Highway Rest Areas.................................................................................. 9-1

Chapter 10 Woody Material ......................................................................................10-1
10-1 Introduction............................................................................................................................... 10-1
10-1.1 Design Process....................................................................................................... 10-2
10-1.2 Guidance for Emergency Large Woody Material Placement ............... 10-3
10-2 Reach Assessment................................................................................................................... 10-4
10-3 Risk Assessment....................................................................................................................... 10-4
10-3.1 LWM and MWM Risk Assessment ................................................................ 10-4
10-3.2 Recreational Water Safety Risk Assessment.............................................. 10-7
10-3.3 FEMA and Local Floodplain Permit Requirements................................... 10-9
10-4 Design .......................................................................................................................................... 10-9
10-4.1 Bank Protection Design Criteria...................................................................... 10-9
10-4.2 Habitat Enhancement Design Criteria ........................................................10-12
10-4.3 Stability ...................................................................................................................10-18
10-4.4 Scour........................................................................................................................10-22
10-5 Inspection and Maintenance .............................................................................................10-23
10-6 Appendices...............................................................................................................................10-23

Glossary and Sources...................................................................................................................... 1

Abbreviations.................................................................................................................................................. 1
Main Glossary of Terms .............................................................................................................................. 6
Sources ............................................................................................................................................................18

WSDOT Hydraulics Manual M 23-03.11 Page vi

April 2025
Figures
Figure 2-1 Extended Precipitation Time Series Regions .........................................................................2-20

Figure 2-2 Precipitation Station Selection outside Extended Precipitation Time Series
Regions ................................................................................................................................................2-21

Figure 2-3 Rational Formula Example ............................................................................................................2-25

Figure 3-1 Headwater and Tailwater Diagram.............................................................................................. 3-8

Figure 3-2 Roadway Overtopping ..................................................................................................................... 3-9

Figure 3-3 Typical Bottomless Culvert...........................................................................................................3-10

Figure 3-4 Projecting End ...................................................................................................................................3-13

Figure 3-5 Beveled End Section .......................................................................................................................3-14

Figure 3-6 Headwall..............................................................................................................................................3-15

Figure 3-7 Modified Wing Wall for Circular Pipe ......................................................................................3-16

Figure 3-8 Rock-Protected Outlet...................................................................................................................3-17

Figure 3-9 Camber under High Fills ................................................................................................................3-19

Figure 3-10 Culvert Angle Point .........................................................................................................................3-20

Figure 3-11 Typical Twin-Barrel Inverted Siphon ........................................................................................3-21

Figure 4-1 Field Slope Measurement of Uniform Flow Channels Plan View .................................... 4-3

Figure 4-2 Field Slope Measurement of Uniform Flow Channels Section View.............................. 4-3

Figure 4-3 Field Slope Measurement of Non-Uniform Flow Channels Plan View.......................... 4-4

Figure 4-4 Field Slope Measurement of Non-Uniform Flow Channels Section View.................... 4-4

Figure 4-5 Field Slope Measurement of Uniform Flow Channels Profile View................................ 4-5

Figure 4-6 Field Slope Measurement of Non-Uniform Flow Channels Profile View ..................... 4-5

Figure 4-7 Typical Cross Section of Rock Bank Protection Installation .............................................. 4-9

Figure 4-8 Potential Deliverables for Permitting Process.......................................................................4-12

Figure 5-1 Sag Analysis.......................................................................................................................................... 5-6

WSDOT Hydraulics Manual M 23-03.11 Page vii

April 2025
Figures

Figure 5-2 Drainage Ditch Detail ....................................................................................................................... 5-9

Figure 5-3 Grate Inlet Type 1 Structure ........................................................................................................5-11

Figure 5-4 Grate Inlet Type 2 Structure ........................................................................................................5-12

Figure 5-5 Rectangular Vaned Grate and Rectangular Bi-Directional Vaned Grate.....................5-14

Figure 5-6 Section and Isometric View Combination Inlet Frame, Hood, and Vaned Grate .....5-15

Figure 5-7 Grates A and B ..................................................................................................................................5-16

Figure 5-8 Frame and Vaned Grates for Installation on Grate Inlet ...................................................5-16

Figure 5-9 Circular Grate.....................................................................................................................................5-17

Figure 5-10 Herringbone Pattern.......................................................................................................................5-17

Figure 6-1 Storm Sewer Configurations.......................................................................................................... 6-2

Figure 7-1 WSDOT Lateral Migration Risk Assessment Process........................................................... 7-9

Figure 7-2 Styles of Knickpoint Evolution....................................................................................................7-17

Figure 7-3 WSDOT Long-Term Degradation Assessment Process ....................................................7-18

Figure 7-4 Reference Reach Determination ................................................................................................7-22

Figure 7-5 Final Design Cross Section ...........................................................................................................7-27

Figure 7-6 Minimum Hydraulic Width and MHO......................................................................................7-28

Figure 7-7 Streambed Material Design Methodology..............................................................................7-37

Figure 7-8 Formation of an Armor Layer ......................................................................................................7-39

Figure 7-9 Meander Bar Detail .........................................................................................................................7-42

Figure 7-10 Typical Stream Morphologies Suitable for Meander Bar Application ..........................7-43

Figure 7-11 Range of Slopes Suitable for Meander Bar Application.....................................................7-44

Figure 7-12 Meander Bar Spacing Detail.........................................................................................................7-46

Figure 7-13 Forced Bar vs. Free Bar Threshold ............................................................................................7-46

Figure 7-14 Typical Point Bar Formation in Meandering Streams.........................................................7-49

Figure 7-15 Example Velocity Maps..................................................................................................................7-51

Figure 7-16 Example of a Constructed Meander Bar with Slash............................................................7-52

WSDOT Hydraulics Manual M 23-03.11 Page viii

April 2025
Figures

Figure 7-17 Example of Constructed DGC Feature, 2 Years after Construction.............................7-53

Figure 7-18 DGC Details........................................................................................................................................7-54

Figure 7-19 Total Scour Components without Potential of Lateral Migration..................................7-59

Figure 7-20 Total Scour Components with Potential of Lateral Migration ........................................7-60

Figure 7-21 Scour Countermeasure Design with Deep Foundation and Calculated
Abutment Scour Greater than Zero..........................................................................................7-62

Figure 7-22 Scour Countermeasure Design with Deep Foundation and Calculated
Abutment Scour of Zero ...............................................................................................................7-62

Figure 7-23 WSDOT’s Performance Management Process.....................................................................7-68

Figure 8-1 Typical Soil Pressure Surrounding a Pipe Arch ....................................................................... 8-4

Figure 8-2 Concrete Thrust Beams Used as Longitudinal Stiffeners.................................................... 8-5

Figure 8-3 Typical Corrugation Section.........................................................................................................8-11

Figure 8-4 Typical Spiral Rib Section..............................................................................................................8-12

Figure 8-5 Typical Profile Wall PVC Cross Sections.................................................................................8-15

Figure 8-6 Washington State Corrosion Zones ..........................................................................................8-18

Figure 8-7 Corrosion Zone I: Flow Chart of Acceptable Pipe Alternatives and Protective
Treatments .........................................................................................................................................8-19

Figure 8-8 Corrosion Zone I: Acceptable Pipe Alternatives and Protective Treatments............8-20

Figure 8-9 Corrosion Zone II: Flow Chart of Acceptable Pipe Alternatives and Protective
Treatments .........................................................................................................................................8-21

Figure 8-10 Corrosion Zone II: Acceptable Pipe Alternatives and Protective Treatments...........8-22

Figure 8-11 Corrosion Zone III: Flow Chart of Acceptable Pipe Alternatives and Protective
Treatments .........................................................................................................................................8-23

Figure 8-12 Corrosion Zone III: Acceptable Pipe Alternatives and Protective Treatments .........8-24

Figure 8-13 Replace or Rehabilitate Decision Tree .....................................................................................8-30

Figure 8-14 Deflection of Flexible Pipes .........................................................................................................8-34

Figure 8-15 Zones of Tension and Compression in Rigid Pipes..............................................................8-35

Figure 8-16 Decision Tree for Pipe(s) to be Abandoned ...........................................................................8-37

WSDOT Hydraulics Manual M 23-03.11 Page ix

April 2025
Figures

Figure 8-17 Pipe abandonment determination schematic........................................................................8-38

Figure 8-18 Pipe Minimum Cover ......................................................................................................................8-39

Figure 10-1 Wood Design Process ....................................................................................................................10-3

Figure 10-2 Large Wood Property Damage Risk Matrix (modified from NOAA 2011).................10-5

WSDOT Hydraulics Manual M 23-03.11 Page x

April 2025
Tables
Table 1-1 Hydraulic Report Documentation................................................................................................ 1-5

Table 1-2 Design Reference.............................................................................................................................1-20

Table 2-1 Methods for Estimating Runoff Rates and Volumes............................................................. 2-4

Table 2-2 Runoff Coefficients for the Rational Method: 10-Year Return Frequency.................. 2-9

Table 2-3 Ground Cover Coefficients...........................................................................................................2-11

Table 2-4 Index to Rainfall Coefficients.......................................................................................................2-13

Table 2-5 Total 5-Day Antecedent Rainfall................................................................................................2-17

Table 2-6 Relationship between NRCS Hydrologic Soil Group and MGSFlood Soil Group
................................................................................................................................................................2-22

Table 3-1 Field Data Requirements for Hydraulic Reports and Specialty Reports........................ 3-3

Table 3-2 Information for the Hydraulics and Specialty Reports for New Culverts and for
Extending/Replacing Existing Culverts...................................................................................... 3-4

Table 3-3 Outlet Protection Material Size ..................................................................................................3-18

Table 4-1 References for Manning’s Roughness Coefficients............................................................... 4-7

Table 5-1 Design Frequency and Allowable Spread.................................................................................. 5-4

Table 5-2 Properties of Grate Inlets..............................................................................................................5-18

Table 6-1 Minimum Storm Sewer Slopes ...................................................................................................... 6-4

Table 7-1 Stream Team Responsibilities........................................................................................................ 7-3

Table 7-2 Flood Event for Hydraulic Design Elements..........................................................................7-24

Table 7-3 100-Year Design Freeboard Requirements on Buried Structures.................................7-33

Table 7-4 Maintenance Clearance for Complexity Features ...............................................................7-35

Table 8-1 Pipe Abrasion Levels .......................................................................................................................8-27

Table 8-2 Concrete Pipe ....................................................................................................................................8-40

Table 8-3 Concrete Pipe for Shallow Cover Installations......................................................................8-40

Table 8-4 Corrugated Steel Pipe: 2⅔ in. × ½ in. Corrugations—AASHTO M 36...........................8-41

WSDOT Hydraulics Manual M 23-03.11 Page xi

April 2025
Tables

Table 8-5 Corrugated Steel Pipe: 3 in. × 1 in. Corrugations—AASHTO M 36...............................8-41

Table 8-6 Corrugated Steel Pipe: 5 in. × 1 in. Corrugations—AASHTO M 36...............................8-42

Table 8-7 Corrugated Steel Structural Plate Circular Pipe: 6 in. × 2 in. Corrugations................8-42

Table 8-8 Corrugated Steel Pipe Arch: 2⅔ in. × ½ in. Corrugations—AASHTO M 36................8-43

Table 8-9 Corrugated Steel Pipe Arch: 3 in. × 1 in. Corrugations—AASHTO M 36....................8-44

Table 8-10 Corrugated Steel Structural Plate Pipe Arch: 6 in. × 2 in. Corrugations......................8-45

Table 8-11 Aluminum Pipe: 2⅔ in. × ½ in. Corrugations—AASHTO M 196......................................8-46

Table 8-12 Aluminum Pipe: 3 in. × 1 in. Corrugations—AASHTO M 196..........................................8-46

Table 8-13 Aluminum Structural Plate: 9 in. × 2 in. Corrugations with Galvanized Steel
Bolts ......................................................................................................................................................8-47

Table 8-14 Aluminum Pipe Arch: 2⅔ in. × ½ in. Corrugations—AASHTO M 196...........................8-47

Table 8-15 Aluminum Pipe Arch: 3 in. × 1 in. Corrugations—AASHTO M 196...............................8-48

Table 8-16 Aluminum Structural Plate Pipe Arch: 9 in. × 2⅔ in. Corrugations, ¼ in. Steel
Bolts, 4 Bolts/Corrugation............................................................................................................8-48

Table 8-17 Steel and Aluminized Steel Spiral Rib Pipe: ¾ × 1 × 11½ in. or ¾ × ¾ × 7½ in.
Corrugations—AASHTO M 36....................................................................................................8-49

Table 8-18 Aluminum Alloy Spiral Rib Pipe: ¾ × 1 × 11½ in. or ¾ × ¾ × 7½ in.
Corrugations—AASHTO M 196 .................................................................................................8-50

Table 8-19 Thermoplastic and Ductile-Iron Pipe ........................................................................................8-50

Table 10-1 Physical Characteristics of Woods Found in the Pacific Northwest.......................... 10-11

Table 10-2 Large Wood Target Metrics ...................................................................................................... 10-17

WSDOT Hydraulics Manual M 23-03.11 Page xii

April 2025