What is Horizontal Directional Drilling?
Dewberry Graduate Engineer Seth Widner describes horizontal directional drilling in about 180 seconds.
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Hi, my name is Seth Widner and I'm a graduate engineer at the Denver, Colorado, office. And today I'm going to be talking about horizontal directional drilling. Horizontal directional drilling, or HDD, is a trenchless technology used to install new underground utilities such as a water line or sewer line. Typically, when you install these new lines, you dig up some dirt, put your pipe in the ground and cover it back up. However, what happens if this is not possible? Let's say there is a river or a busy intersection that needs to be crossed. What do you do? Well, one option is to directly drill underneath those obstacles and pop back up on the other side. This is what HDD is all about. So, how does HDD work? A study uses a machine known as a drill rig that sits on top of the ground and launches a drill bit into the earth.
From here, the drill operator can steer the drill bit around and underneath any obstacles in the way. The drill bit is attached to a long string of flexible steel rods that help push the drill bit through the earth. Once all the obstacles have been avoided, the drill bit starts heading back up to the surface and pops out at a known location. This creates a small hole known as the pilot bore. Usually, the pilot bore is not wide enough to install your new utility. So the drill bit is detached from the end of the rods, and a cutting device known as a reamer is attached. A reamer, also known as a back reamer, comes in many different shapes and sizes, and the goal of these is to widen the pilot board gradually.
This is accomplished by using the drill rig to pull the reamer back through the pilot bore, widening the hole as it makes its way back to the machine. Once the hole is large enough and cleared of any remaining soil, the new utility is hooked up to the drill rig and pulled through the hole, completing the process. It's a good idea to keep horizontal directional drilling in mind when designing new underground utilities, especially in heavily constrained areas. Trenchless crossings will become more important as less room is available for new underground utilities. And HDD is one solution to that problem.