Directional Boring (Horizontal Directional Drilling)
Directional Boring (Horizontal Directional Drilling)
Competence, Strong Safety Practices, and the latest in Horizontal Boring Technology deliver trenchless utility installation services for a modern world.
Trenchless boring technologies enable the installation of conduit, pipeline, telecom, and fiber without the need for excavation. All South Underground utilizes the latest in horizontal boring technology to install pipeline and conduit up to 6″ in diameter supporting water, gas, sewer, electrical, and telecommunications functions.
In many cases Directional Boring is the only way to install utilities from one point to another without disturbing surface features or risking damage to existing critical infrastructure. All South Underground performs Horizontal Directional Boring to install utilities under existing roads, sidewalks, waterways, buildings, and other obstacles.
- Locate Existing Utilities – It’s important to know where existing utilities may lie prior to beginning any boring or excavating operations. All South utilizes the state’s 811 locating service as well as private locating to ensure that boring operations will not disturb buried services. Technologies such as Ground Penetrating Radar (GPR), Electromagnetic Induction (EMI), and hydro-excavation are used to designate (“mark”) and uncover (“daylight”) existing subsurface utilities. Proper marking and valid locate tickets are an important aspect of reducing the risk of directional boring activities.
- Site Survey – Prior to creating the work-plan, a boring foreman or project manager conducts a site-survey to ensure that all potentially knowable information regarding the jobsite and existing utilities has been considered. The presence of water hydrants, utility boxes, or other topside features is reconciled with previously performed locates to ensure that nothing has been overlooked. Some buried utilities may be vacuum excavated to visually verify their depth, position and orientation.
- Pre-Work Planning & Safety Meeting – The Bore-Team foreman creates a work plan detailing each step of the work to be performed. Consideration is made for both topside and buried hazards (electrical, soil stability, traffic, etc.). An on-site pre-work meeting is held to ensure that each team member understands the work plan, is equipped with necessary Personal Protective Equipment (PPE), and is made aware of all potential safety hazards present on the work site. Safety barriers, maintenance of traffic (MOT), and visual aids are setup at this time.
- Drill Setup & Mud Mixing – Staging of the directional drill, conduit/pipe, and ancillary equipment is performed while drilling mud is mixed to prepare for drilling operations. Entry and exit pits may be excavated at this time.
- Drilling Begins – An experienced drill operator and drill head locator lead the drilling operation. As the drill head penetrates the earth, additional drill rods are added as needed to extend the length of the drill path.
- Drill Steering (drill-head locating) – The drill operator steers the drill head under and around existing obstacles and buried utilities using guidance data provided by an electronic beacon located inside the drill head.
- Drill Head Exit – As the drill path reaches its terminus, the drill head exits at a predetermined location.
- Reaming & Pull-Back – The bore head is replaced with a reamer and attached to the pipe/conduit to be installed via a swivel. Bore mud is pumped through the drill rods to hold the bore open and provide lubrication while the pipe/conduit is pulled back through the original bore path. Installation of larger pipe/conduit may require additional reaming pull-backs prior to pulling the pipe/conduit.
- Site Cleanup and Restoration – Extraneous bore mud and spoils are removed with a vacuum excavator. Surface features such as sod, asphalt, and curbing are restored to their original condition.
- Bore Log & Report Submission – A written report detailing the utilities installed along with a bore log indicating depth and path information is provided to the customer.
Basic Directional Drilling Parameters:
Directional Drilling can be performed in virtually all soil types and conditions.
Typical Single Bore Path Length: 200-400′
Typical Pipeline/Conduit Diameter: Up to 6″
Combinations of Smaller Conduits Can Be Installed Simultaneously
Composition of Drilling Mud: Primarily Refined Bentonite Clay & Water (non-toxic)
Directional Drill Bits (various soil conditions)
Missile Boring Service – For installation of shorter runs of pipe/conduit under 3″ in diameter, All South Underground also offers missile boring services.
Missile Boring, sometimes referred to as “mole boring”, is a process that involves the use of an air-powered percussion tool (“missile”) that punches its way through soil, opening up a bore path in its wake. A “missile” bore is not steerable, and works best in reasonably dry soils. Missile boring is typically utilized for single bores under 50′ or for longer bores where progress pits may be excavated every 40-60′ to extend the bore path.
Missile Boring – Steps:
- Entry Pit: An entry pit is excavated such that the “missile” may be positioned to begin the bore.
- Aim & Shoot Bore “Missile”: The “missile” is carefully aimed, taking into account soil conditions and desired path. A large air compressor supplies air to the missile, powering its repetitive percussive action.
- Progress Pit – Re-Aim: If a change of direction or a path of longer than 50′ is desired, progress pit is used to receive and re-aim the missile towards the next pit; a new “shot” is begun.
- Exit Pit: A final Exit Pit is excavated to collect the missile at the terminus of the bore path.
- Utility Installation: Depending upon the conditions, pipe/conduit is pushed or pulled through the bore path from pit to pit, resulting in a continuous length of installed utility.
- Cleanup and Restoration: After missile boring operations are complete, the site is cleaned up and restored to its original condition.