Installation of underground utilities has traditionally involved open trenching. The contractor had to excavate around existing utilities to get to the depth required to install conduit. Costly sidewalks, pavement, brick paving, sod and other surfaces had to be cut open and replaced. There was always a risk of hitting existing underground utilities during excavation. Additionally, the excavation usually causes interruption of traffic and is an inconvenience to nearby businesses.

Advantages of HDD over Other Methods

HDD equipment requires a relatively short set-up time; a directional drilling rig can be set up and boring can begin within an hour. Labor requirements are minimal, as it only takes a small crew to operate a directional drilling rig.

The need for traditional excavation during horizontal directional drilling is minimal or non-existent. In crowded urban areas, horizontal directional drilling is increasingly viewed as the preferred technology because:

• Surface disruption is minimized.
• Less negative impact to residents and businesses.
• HDD eliminates the need for removal, restoration and long-term costs associated with trench settlement.
• In open areas, horizontal drilling provides an efficient method for crossing obstacles, such as rivers, highways, rail tracks or active runways.

HDD Applications

Horizontal Directional Drilling (HDD) — also called directional boring and directional drilling — is a method of installing underground pipes and conduits from the surface along a prescribed bore path. Installation lengths up to 6500' have been completed and diameters up to 48" have been installed in shorter runs. Most installations are considerably shorter and smaller in diameter.

The process is used for installing telecommunications and power cable conduits, water lines, sewer lines, gas lines, oil lines, product pipelines and casings used for environmental remediation. It is used for crossing waterways, roadways, congested areas, environmentally sensitive areas and any area where other methods are more expensive or not feasible. Use of HDD is growing rapidly and is expected to continue to increase for the foreseeable future.

HDD is used in place of other techniques for the following reasons:

• Less traffic disruption
• Lower cost
• Deeper installation possible
• Longer installation possible
• No access pit required
• Shorter completion times
• Directional capabilities
• Safer for the environment

The HDD Procedure

Planning

Every project begins with thoughtful planning. Ground conditions are determined, surrounding utilities positively located, bore profile is surveyed and plotted, safety and environmental issues are considered before work commences.

Pilot Hole

The process begins when the Direction Drill machine pushes a bore head connected to hollow pipe into the ground at an angle. As each joint of drill pipe is pushed into the ground, a new one is added behind it. This process is continued until the bore head comes out of the ground at the end of the bore.

Guiding and Steering the Bore Head

The most commonly used equipment for determining the location of the bore head is called a ‘Walk Over’ Locating system, such as a Sonde (Transmitter), behind the bore head, which registers angle, rotation, magnetic direction and temperature data. The information is then encoded into an electro-magnetic signal, which is transmitted through the ground to the surface. At the surface, a receiver is manually positioned over the Sonde signal, the signal is decoded and steering directions are relayed to the operator of the drill machine.

Drilling Fluid

From the drill head flows a high-pressure jet of drilling (boring) fluid, which is generally a mixture of bentonite clay and water. Boring is accomplished through the cutting action of the jet of fluid and/or a rotating drill bit. The drill fluid cuts soil, suspends and carries cuttings out of the bore hole, seals the bore hole, lubricates and cools the pipe.

Reaming

Upon reaching the exit point, the bit is detached and the end of the drill pipe is attached to a reamer. The reamer is pulled back while rotating the drill pipe with as many passes as required to open up the correct diameter of hole to allow the pipe to be installed.

Pull Back

Once the bore hole is the correct size for the pipe to be installed, it is attached to the end of the reamer and pulled through the hole. Throughout this process, bore fluid is being continually pumped into the hole to ensure that the hole is sealed with no void being left between the pipe and the native soil.

Call Diversified Underground at 303-636-9999 for a detailed free estimate. We will be happy to meet you at your job site for a project walk-through.