HORIZONTAL DIRECTIONAL DRILLING NOT EVERY BORE IS BORING

Florida Chapter APWA - 2013 Annual Meeting and Trade Show

April 24, 2013

Jason Sciandra, P.E.

Pipe Pullback

Outline

• Overview of HDD

• Overview of case study

• Design considerations

• Geotechnical investigation and laboratory testing program

• Contract specifications

• Submittal process

• Critical factors during construction

Horizontal Directional Drilling Overview

• Surface conflicts (e.g., waterways, major road, buildings)

• Subsurface conflicts (e.g., existing utilities and infrastructure)

• Environmental regulation (e.g., wetlands)

Case Study Overview

Intake

WWTP

Difficult

Property

Owner

Environmentally

Sensitive Areas

Two HDDs

Weir

Case Study Overview (Cont.)

Entry Pit

Exit Pit

Case Study Overview (Cont.)

Exit Pit

Pipe Laydown Area

Blocked Off

Staging Area

Design Considerations

• Preliminary pull-back calculations – contractor should confirm

– Tensile stress, stretching

– Type of machine required

– Pipe material

• External force on the pipe (soil pressure) – contractor should confirm

• Pipe material – HDPE vs. Fusible PVC vs. other

Design Considerations – Pipe Material Selection

Design Considerations – Pipe Material Selection

Geotechnical Investigations

• Number and type of soil borings

• Types of soil borings

– Shallow land borings

– Deep land borings

– Deep water borings

Geotechnical Investigations (Cont.)

• Key findings:

– Mixed face

– Weathered, fractured limestone

• Store samples until project completion

Contract Specifications

• Competitive procurement – can’t just choose best contractor

• Specifications can be used to establish minimum experience criteria

– Project Example:

Submittal Process

• Two Objectives:

– Document the contractor’s equipment and approach

– Engage contractor in the thought process of completing the work

Submittal Process (Cont.)

Typical submittals:

1. Contact Grouting Plan

2. Contingency Plan for Remediation of Potential Problems

3. Disposal of Spoils and Drilling Fluids Plan

Submittal Process (Cont.)

4. Equipment Layout Plan

Submittal Process (Cont.)

4. Equipment Layout Plan

Submittal Process (Cont.)

4. Equipment Layout Plan

Submittal Process (Cont.)

5. Inadvertent Return and Surface Spill Contingency Plan

6. Horizontal Directional Drilling Work Plan

Maximum Allowable Mud Pressure for Hydraulic Fracture

Submittal Process (Cont.)

7. Maximum Allowable Drilling Fluid Pressure Calculations

Maximum Allowable Mud Pressure for Shear Failure

Submittal Process (Cont.)

8. Methods, Equipment, and Materials Description Plan

9. Pipe Filling Methods and Testing

10. Protection of Adjacent Structures and Facilities Plan

11. Pipe Stress Calculations

Submittal Process (Cont.)

10. Protection of Adjacent Structures and Facilities Plan

Preconstruction

Survey

Submittal Process (Cont.)

12. Pullback Calculations

Pull-back Force and Hyrdokinetic Force

Submittal Process (Cont.)

13. Qualifications

5 Years Experience

Specified Material

Experience

Submittal Process (Cont.)

13. Qualifications

Field

Supervisor

Experience

Submittal Process (Cont.)

14. Radius of Curvature Confirmation

Submittal Process (Cont.)

15. Rig Capacity Plan

16. Safety Plan

17. Schedule

18. Soil Separation Plan

19. Surveying Equipment and Procedures

20. As-built pilot bore profile

21. Daily logs and records

Critical Factors during Construction

• Communication

• Risk mitigation meetings

• Daily bore logs and as-built submittals

Communication

• Keep lines of communication open between:

– Contractor and engineer

– Contractor and owner

– Contractor and subcontractor (if applicable)

– Contractor and property owners

Risk Mitigation Meetings

• Specification requirement: “At least 15 working days prior to each major operations milestone, the CONTRACTOR and HDD superintendent shall attend a risk mitigation meeting with representatives of the ENGINEER and OWNER for each HDD crossing.”

• Milestones can include: – Rig mobilization and setup.

– Pilot bore drilling.

– Pre-reaming and reaming.

– Layout and thermal butt-fusing of pipe.

– Pressure testing of pipe prior to pullback.

– Final reaming and pullback of pipe.

– Pressure testing of pipe after installation.

– Mandrel/pig test to confirm deformations of pipe are within allowable tolerances.

Daily Logs and As-Built Submittals

Plan View

Profile View

Construction Videos – Pipe Layout Side

Construction Videos – Ballast Water

Construction Videos – Drill Rig Side

Construction Photos – Pull Head

Construction Photos – Ream Head

Construction Photos – Pipe Fusing Machine

Conclusion

• Design considerations

• Geotechnical investigation and laboratory testing program

• Contract specifications

• Contractor selection

• Submittal process

• Critical factors during installation

Questions