HORIZONTAL DIRECTIONAL DRILLING

• DESCRIPTION: HDD is a steerable trenchless methodof installing underground pipe, conduit, or cable in ashallow arc along a prescribed bore path by using asurface-launched drilling rig, with minimal impact on thesurrounding area.

• NON-STEERABLE OR STEERABLE: Steerable

• EQUIPMENT: HDD Drill Rig, Steering Tools, HoleOpeners, Drill Pipe, Mud Cleaning Systems, Mud Pumps

• WORKSPACE REQUIREMENTS: No Entrance and ExitShafts are required. Total workspace can exceed 100’Wide x 200’ Long at Entrance and Exit Size is determinedby total pipe requirements typically 8’ wide for thelength of the pipe crossing.

• RANGE: Greater than 12,000’ Have Been Achieved

• DIAMETERS: 2” to 60”

• INSTALLED PIPE: Steel, HDPE, PVC, Polypropylene,Ductile Iron

• CREW SIZE: 2-14 Persons

• DESCRIPTION: Method combines the advantages ofmicro-tunneling & HDD technology. In one step only, aprefabricated pipeline can be installed and the requiredborehole excavated at the same time. Allows speedy andeconomic installation.

• NON-STEERABLE OR STEERABLE: Steerable

• EQUIPMENT: Herrenknecht Microtunnel Boring Machine(MTBM), Herrenknecht Pipe Thruster, Direct Pipe™Launch Seal, Control Cab, Ground Cutting Wheel

• WORKSPACE REQUIREMENTS: Entry Work Site of200’ x 200’, Drilling Fluid System of 100’ x 100’ (AlongPipe String) & Exit Work Site of 50’ X 50’ (MachineRetrieval Only)

• RANGE: Greater than 4,000’

• DIAMETERS: 30” to 60”

• INSTALLED PIPE: Steel, HDPE with Steel Conduit,Bundle Configurations

• CREW SIZE: 17 Persons

DIRECT PIPE® METHOD

METHOD COMPARISON

SAMPLE DESIGN PARAMETERS

EQUIPMENT

LAYOUT

CONCLUSION• In the case of Direct Pipe®, projects with limited space availability, Direct Pipe® has the benefit of

having the equipment & pipe stringing on the entrance side and requires only a mall it on exit. Inaddition, Direct Pipe® has the ability to have shorter and shallower crossing plan and profileconfiguration allowing easier pipeline access from the surface and shorter overall crossing length.Most importantly, this method has significantly lower annual pressure acting on the surroundingsubsurface formation which drastically reduces the potential for inadvertent returns. Thedownside, however, is that the significantly higher cost per foot often detracts potential users frompursuing this method.

• Horizontal Directional Drilling, however, is widely accepted as a go-to trenchless crossing methodand has benefits as well. For example, HDD has been highly successful in hard rock conditionswhere the Direct Pipe® Method has struggled to meet schedule expectations. In addition, HDD ishistorically the less cost per foot solution under most project conditions. Understanding thedelicate balance of each technology’s benefit to a potential project can be difficult to differentiate.

Direct Pipe® Thruster Assembly

ADDITIONAL MAJOR EQUIPMENT

• Soft Ground / Rock Cutting Wheel with Cutting Diameter of 43

• Drilling Fluid Recycling System CS-514 or Similar

• Typical Spare Parts: Fittings, Couplers, Sensors, Power Chords, Communication Chords, PowerControl Modules, HWL Line, Electric Pumps, Suction/Discharge Plumbing, And Interface Components

MICROTUNNELING NAVIGATION/GUIDANCE SYSTEM

• Universal Navigation System Integral Module: Steering/Guidance

• Gyro Navigation System (GNS): Calculates True North Relative to MTBM axis.

• Coupled Navigation: Calculates Current Position of the MTBM.

• Hydrostatic Water Levelling: Used to Obtain Elevation Data.MTBM Entering Launch Seal

Separation Equipment

Control Cab / Navigation Console

Entry Pit Foundation at Launch Shaft Entry Side Tunneling Operations

Exit Side / Pushing OutEntry Side Support Operations

Example Direct Pipe® Factory of Safety Chart

Example Direct Pipe® Annular & Limit Pressure Chart

PRESENTATION OVERVIEWDeciding the appropriate trenchless construction method can often be difficult decision for projectowners and trenchless engineers. While project cost is most often the deciding factor, many projectshave many factors that need to be appropriately evaluated and prioritized early in the process in otherto avoid unforeseen costs later. The goal of this poster is to provide a general overview of the DirectPipe® Method and present how it compares to Horizontal Directional Drilling in order to educate projectstakeholders and assist in selecting the most appropriate method for design.

Direct Pipe® Method Vs. HDD | Annular Pressure Comparison

Further studies are scheduled to develop a decision making framework for owners to use early in thedesign process to select the most appropriate method for critical crossings. This framework will takeinto account factors such as construction space availability, geotechnical conditions, and project timeline.Additional factors including project schedule, health and safety, and project value will also be included.The development of this tool will build on ongoing collaboration between project stakeholders includingproject owners, engineers, construction managers, field personnel and safety professionals.