Directional Drilling Explained

Horizontal Directional Drilling (HDD) is a method for installing underground utilities (ie: water, sewer, electricity, gas, telecom, etc.) with minimal disruption to the surface. In the beginning, HDD was primarily used to install utilities under roads and rivers. In the mid 1990s, the telecom industry embraced HDD technology and started utilizing it for entire projects. The Horizontal Directional Drilling industry was fueled by the telecom industry's explosive growth from 1995 - 2000. However, the other utilities have been slow to embrace HDD technology. This is largely due to a lack of understanding of the HDD process, as well as the misconception that HDD is an expensive method for installing utilities. The reality is that HDD can be very price competitive with open cut methods, especially if one considers the reduced restoration costs and lower social costs involved with an HDD installed utility.

The Horizontal Directional Drilling process is really quite simple. It consists of a machine which has the capacity to push, pull, and rotate drill rod. Drill rod is nothing more than threaded steel pipe that has been specially formulated to withstand bending and rotational torque without damaging the pipe itself.

A drill head is attached to the front of the drill rod. The drill head has a hollow cavity in it which houses a transmitter. The transmitter emits a signal which provides the HDD crew information as to the depth, pitch, and rotational position of the drill head.

A tapered cutting bit is attached to the front of the drill head. It is the taper on the cutting bit that provides the steering. The HDD operator positions the taper in the direction that steer is required and thrusts the drill rod forward with no rotation. Once the proper amount of steering is achieved, the HDD operator resumes rotation and thrust of the drill rod. As long as the drill rod is rotated, the drill head will continue to maintain the course that it is on with minimal deviation.

Drill rods can vary in length depending on the size of the HDD machine being utilized. Once the HDD machine has reached its full stroke, the rotational gearbox is disconnected from the drill rod that was just installed and another section of drill rod is added. This process is continued until the drill head reaches the destination point.

Once the destination point is reached, the drill head is removed from the drill rod and a reamer is attached. The reamer cuts a larger hole to allow enough room for the product being installed. The product is attached to a swivel behind the reamer and is pulled into the ground while the reamer is being rotated and pulled back towards the machine. Every time the machine reaches its full stroke, a drill rod is removed and the rotational gearbox is attached to the next drill rod. This process continues until the product has been pulled back to the HDD machine.

Wampler gives talks and training sessions (like the one above) about directional drilling and soil remediation