INDOT Culvert Sizing Policy Purdue Road School March

INDOT Culvert Sizing Policy Purdue Road School March 9, 2011

Your Presenters: John Bartolo, PE & Crystal Weaver, PE INDOT Office of Hydraulics

The Goal for Policy is a Clear Understanding!

Design Storm Frequency

Allowable Headwater New Alignment n n 0. 14 ft. Maximum Backwater Special Cases: n n Backwater Dissipates 0. 14 ft. or Less at R/W Backwater is Contained in the Channel n n Remember to Check Outlet Velocity! Flood easements are purchased n Very rare and only on large projects

Allowable Headwater Replacing an Existing Culvert n n Match or Reduce Existing Backwater Exception: n Existing Backwater Exceeds 1 ft.

Allowable Headwater Other Constraints n n n Grade of Adjacent Driveways Finished Floor Elevation of Adjacent Buildings Elevation of Surrounding Crop Land

Allowable Headwater Other Constraints

Roadway Serviceability n For a Q 100 Design Storm n n 2 ft. Below Edge of Pavement For Design Storms Less Than Q 100 n Headwater Can Not Exceed Edge of Pavement

Maximum Outlet Velocity n n Revetment Riprap < Class 1 Riprap > Class 2 Riprap > Energy Dissipator > n 6. 5 ft/s < 10 ft/s < 13 ft/s See Chapter 34 in the Indiana Design Manual

Minimum Outlet Velocity n Typical Minimum Outlet Velocity n 3 ft/s

Do Not Consider Storage at the Culvert

Priority System n n n Trial Trial 1 2 3 4 5 6 - Single Circular Pipe Single Deformed Pipe Single Specialty Structure Multiple Circular Pipes Multiple Deformed Pipes Multiple Specialty Structures

Pipe Culvert Interior Designation n Smooth Interior: n n Manning’s n = 0. 012 Corrugated Interior: n Manning’s n = 0. 024

Minimum Culvert Size Structure Application Minimum Circular Pipe Size Minimum Deformed Pipe Size Driveway Culvert 15 inch 1. 1 ft 2 Mainline/Public Road Approach Culvert (2 lanes) 15 inch 1. 1 ft 2 Mainline/Public Road Approach Culvert (3 + Lanes) 36 inch 6. 7 ft 2

Culvert Extension Process n n Match Existing Culvert Size and Type Perform Appropriate Hydraulic Analysis

Culvert Sumping Three Sided Structures n Sump structure n n n 18 inches for sand 12 inches for other soils 3 inches for rock or till Structure should not increase in size See standard drawing for stream bed and scour information

Culvert Sumping Boxes and Pipes

Culvert Sumping Boxes and Pipes n n Structure may increase in size, if sump is more than 3 inches Hydraulic modeling may be needed to check capacity.

Approved Design Methods n Computer Method n n FHWA Program HY-8 Hand Method n n Nomographs From FHWA Publication HDS #5 “Hydraulic Design of Highway Culverts” Available as a Printed Manual, on CD ROM or online

Design Responsibility § All Types of Projects n n Consultant Will Size the Culvert(s) INDOT Hydraulics Will Review Computations

Where Do I Get More Information? n n INDOT Design Manual Part IV Hydrology and Hydraulics FHWA Hydraulics Home Page n n n Hydraulics Engineering Publication List Hydraulics Engineering Software Reference List www. fhwa. dot. gov/engineering/hydraulics/

Questions www. fhwa. dot. gov/engineering/hydraulics/