Directional drilling sounds technical, but the idea is simple: it lets us install underground utilities without tearing up roads, lawns, streams, or sidewalks. For homeowners, municipalities, and contractors alike, it’s often the cleanest, most cost-effective way to run new pipes, cables, or conduits from point A to B.
Here at L&N Zimmerman Excavating, we’ve specialized in trenchless utility installation for over two decades. We tackle tough jobs across Pennsylvania, Maryland, and Delaware, from private residential bores to large-scale municipal crossings under railroads, creeks, and highways. This guide breaks down what horizontal directional drilling (HDD) actually involves, when it’s the right tool for the job, and what you can expect from the directional drilling process.
What Is Horizontal Directional Drilling?
Horizontal directional drilling—also called HDD—is a trenchless method used to install underground utilities along a predetermined path without the need for open trenches. Instead of digging up the surface, we drill a steerable bore hole beneath the ground and pull the pipe through it!
HDD is commonly used to install sewer lines, water mains, gas pipes, electric conduits, and fiber optic lines. It’s an especially smart choice in urban areas, under highways or parking lots, and across environmentally sensitive zones where traditional excavation would cause damage.
How the Horizontal Directional Drilling Process Works
The directional drilling process typically involves a two- or three-stage sequence, depending on pipe size.
The first stage is drilling the pilot hole. Using a drilling rig equipped with a drill bit and steerable drill head, the directional driller guides the drill pipe along a planned bore path. Real-time tracking with a beacon housing and magnetic field sensors helps the drill follow the proper alignment.
Next comes pre-reaming (also called back reaming) for larger diameters. A reamer tool enlarges the small diameter pilot hole into a wide enough path for the product pipe.
Finally, the third stage is pipe pullback. The product pipe—often high-density polyethylene (HDPE)—is attached to the drill string and pulled back through the bore hole.
Drilling Fluid: Disposal Is a Must!
Drilling fluid, typically a bentonite-water mixture, is pumped through the drill stem to cool the drill bit, lubricate the drill hole, stabilize the bore, and remove solids. This fluid becomes a slurry that exits at the entry and exit points and must be properly disposed of per environmental guidelines.
Drilling fluid also helps reduce torsional stress on the equipment, especially in long bores or unstable soil conditions.
So When Is Directional Drilling the Better Choice?
Directional boring is a great fit for:
- Utility crossings under roads, driveways, or railroads
- Jobs involving asphalt, concrete, or landscaping you want to avoid disturbing
- Installations near wetlands, streams, or creeks where surface impact must be minimized
- Urban projects where open trenching would block traffic or disrupt surrounding infrastructure
We’ve seen it all: sewer lines under main streets, gas pipe installations in tight job sites, even long-distance pipe pullbacks through challenging terrain.
Clear Advantages of Horizontal Directional Drilling
Horizontal directional drilling minimizes surface disruption. It avoids tearing up pavement or topsoil and reduces environmental impact by drilling under obstacles instead of through them.
It’s often faster and more cost-effective than traditional excavation, especially when factoring in the cost of restoration. It also allows for careful planning around existing underground infrastructure.
With the ability to steer the drill head in real time, construction crews can install product pipe with precision, even around bends or elevation changes. HDD is one of the most flexible, efficient trenchless methods available.
The Challenges, and How We Solve Them
No directional drill is without its challenges. We prepare for each job site with thorough planning and field experience.
- Rocky conditions: If the bore path includes cobble or limestone, drilling gets slower and may require specialized drilling equipment or downhole motors.
- Permitting: In Pennsylvania, horizontal drilling across waterways often requires DEP permits. We understand the permitting process and can help with compliance.
- Slurry disposal: Used drilling fluid must be transported to an approved disposal facility—we handle that as part of our turnkey service.
- Pipe compatibility: HDPE is our go-to product line, but it requires fusion adapters to connect with existing ductile iron or PVC. We plan for this upfront.
Real Jobs We’ve Completed with HDD
- Installed 17,000 ft of 4” HDPE low-pressure sewer in Northumberland County
- Completed 190 ft and 165 ft directional drills under streams using 20″ HDPE
- Performed 3×48″ steel casing jack-and-bores under a Norfolk Southern rail line
- Pulled a 16” FPVC casing under York County roads for a water main project
From small diameter pilot holes in rural farms to complex multi-stage bores in urban environments, L&N Zimmerman has the HDD experience to deliver.
Is HDD Right For You? Let’s Talk About Your Excavating Project!
If you’re planning underground utility work and want a quote or just some insights, give us a call. We’ll let you know if horizontal directional drilling is the right fit — and if it is, we’ll work together to handle every step with precision, care, and decades of field-tested know-how. We’re the directional drilling company near you!