A Trenchless Approach to Underground Utility Installation
Horizontal directional drilling is commonly used when an underground utility needs to cross beneath an area where continuous open trenching would be disruptive, difficult or impractical.
Instead of excavating a trench along the entire route, HDD creates a controlled underground bore between planned entry and exit areas. The utility, conduit or other approved underground product can then be installed through that path.
The method is used on many underground infrastructure projects and is one of several trenchless techniques available to contractors.
How Does Horizontal Directional Drilling Work?
The exact process depends on the project, equipment, underground conditions and installation requirements, but HDD generally follows several planned stages.
1. The Underground Route Is Planned
Before drilling begins, the proposed route needs to be evaluated. Existing utilities, access, surface conditions and the required installation path can all affect the bore plan.
Utility locating, mapping, Ground Penetrating Radar or potholing may be used when additional subsurface information is needed.
2. A Pilot Bore Is Created
A smaller initial bore is drilled along the planned underground route to establish the path the installation will follow.
Directional drilling equipment allows the bore path to be guided through the ground rather than simply drilled in an uncontrolled straight line.
3. The Bore May Be Enlarged
Depending on the size and type of utility being installed, the initial underground path may need to be enlarged before the final product can be placed.
This stage is commonly referred to as reaming.
4. The Utility Is Installed
Once the underground path is prepared, the required utility line, conduit or other approved product can be installed through the bore.
The final installation method depends on the specific utility and project requirements.
HDD Can Reduce Continuous Surface Excavation
Horizontal directional drilling is considered trenchless because it can create an underground route without opening a continuous trench across the entire length of the installation.
Less Continuous Excavation
The entire route does not necessarily need to be opened from the surface.
Existing Surfaces
HDD can be useful when a route needs to pass beneath existing developed or paved areas.
Targeted Access
Excavation may still be required at entry points, exit points, connection areas and other parts of the project.
Where Can Horizontal Directional Drilling Be Useful?
HDD can be considered when continuous open excavation would interfere with existing surfaces, access or site operations.
Roadways
Underground routes may be planned beneath paved roadway areas where project conditions allow.
Driveways
HDD can help reduce the need to continuously open an existing driveway surface.
Parking Areas
Trenchless installation may help reduce surface disturbance across portions of developed parking areas.
Developed Properties
Existing development can make minimizing continuous excavation an important project consideration.
Landscaped Areas
Some routes may benefit from reducing the amount of surface excavation through landscaped areas.
Existing Infrastructure
Trenchless routes may be considered where existing site features affect the proposed installation.
Utility Crossings
HDD may be part of a project where an underground route needs to cross beneath another area or feature.
Constrained Routes
Some sites may have limited areas where continuous trenching is practical.
What Types of Utilities Can Use Directional Drilling?
HDD can support several types of underground utility projects depending on the project design and installation requirements.
Power
Underground routes supporting power-related infrastructure.
Water
Trenchless installation can support certain underground water utility projects.
Gas
HDD may support underground gas infrastructure where the project requirements and conditions are appropriate.
Communications
Underground communications routes can be installed using trenchless methods on suitable projects.
Fiber Optics
Directional drilling is used on underground routes supporting fiber optic infrastructure.
Irrigation & Related Utilities
HDD may also support sleeves and other underground utility infrastructure depending on the project.
Horizontal Directional Drilling vs. Open Trenching
HDD and open trenching are not competing solutions in every situation. Both methods have useful applications depending on the project.
Horizontal Directional Drilling
HDD may be considered when reducing continuous surface excavation is important or when the proposed route needs to pass beneath an existing surface.
- Trenchless underground route
- Reduced continuous surface opening
- Useful for certain crossings
- Requires suitable project conditions
Open Trenching
Open trenching provides direct access to the underground route and may be appropriate where the surface can be opened and excavation fits the project.
- Direct access to the route
- Open excavation along the work area
- Useful for many installation projects
- Can be combined with trenchless methods
Some Projects Use Both Methods
One portion of a utility route may be completed using horizontal directional drilling while another section uses excavation or trenching. The appropriate combination depends on the actual site and project requirements.
Does Directional Drilling Eliminate Excavation?
No. Horizontal directional drilling can reduce continuous excavation along the underground route, but that does not mean the entire project is excavation-free.
Entry and exit areas, connections, tie-ins, access points and other project components may still require excavation.
The amount and type of excavation depend on the project layout, utility being installed and site conditions.
Learn About Excavation ServicesWhy Is Utility Locating Important Before HDD?
Directional drilling takes place underground, so existing buried infrastructure can directly affect the proposed bore path.
Utility Locating & Mapping
Locating can help identify and document known buried utility routes that may affect the project.
Learn MoreGround Penetrating Radar
GPR can provide additional subsurface information where the project calls for further investigation.
Learn MorePotholing
Targeted excavation can physically expose underground infrastructure where direct verification is needed.
Learn MoreNo Single Investigation Method Finds Everything
Subsurface investigation should be planned around the project. Locating, mapping, GPR, potholing and available project information can each provide different types of information.
When Is Directional Drilling Not the Best Choice?
HDD is useful, but it is not automatically the right method for every underground project.
Proposed Route
The geometry and requirements of the underground route affect whether HDD is suitable.
Available Access
The project needs appropriate areas for equipment and the planned installation.
Existing Utilities
Buried infrastructure can affect route planning and the feasibility of a bore.
Surface Conditions
Surface features can influence whether trenchless or open excavation methods make more sense.
Utility Requirements
The type and installation requirements of the utility matter.
Entry & Exit Areas
Suitable areas may be needed for the start and completion of the underground bore.
Project Scope
Different portions of the job may benefit from different construction methods.
Site Conditions
The final approach should be based on conditions at the actual project site.
Horizontal Directional Drilling From Down To Earth Underground
Down To Earth Underground LLC provides horizontal directional drilling and related underground utility services throughout our core Central Florida service area.
We are based in St. Cloud and serve projects in St. Cloud, Kissimmee, Harmony, Lake Buena Vista and communities throughout Osceola County.
Our related services include utility locating and mapping, precision boring, excavation, hand trenching, Ground Penetrating Radar, potholing and underground utility installation and repair.
Frequently Asked Questions About Horizontal Directional Drilling
What does HDD stand for?
HDD stands for horizontal directional drilling, a trenchless method used to create a controlled underground bore for utility installation.
Is horizontal directional drilling trenchless?
Yes. HDD is considered a trenchless method because it can install underground infrastructure without opening a continuous trench along the entire route.
Does HDD require any excavation?
It can. Entry areas, exit areas, tie-ins and other project components may still require excavation even when the primary underground route is completed using directional drilling.
Can directional drilling go beneath paved surfaces?
Directional drilling can be used on projects where an underground route needs to pass beneath existing surfaces, provided the project conditions are suitable for the method.
Is utility locating important before directional drilling?
Existing buried utilities can affect the proposed bore path, so locating, mapping and additional verification may be important parts of project planning.