Every directional boring project starts and ends at the same two points: an entry pit and an exit pit. These bore pits are where the drill rig sets up, where the drill string enters and exits the ground, and where a surprising amount of a project's success or failure gets decided before drilling even begins.
At PL-Enerserv, proper bore pit planning is part of how we deliver directional boring projects safely and on schedule across the Northeast, Midwest, and Southeast United States. This post covers what bore pits are, how they're planned and sized, and why getting them right matters as much as the bore itself.
What Is a Bore Pit?
A bore pit is an excavated opening at the entry or exit point of a directional boring operation. The entry pit is where the drill rig positions itself and where the drill string first enters the ground at a shallow angle. The exit pit is where the pilot bore emerges on the other side of the crossing, and where the product pipe is typically staged before pullback.
Bore pits serve several practical purposes during a bore:
- Giving the drill head a controlled starting point at the correct entry angle
- Allowing crews to monitor and adjust drilling fluid at the surface
- Providing access for the reaming and pullback stages
- Creating a workspace to connect the product pipe to the drill string
Despite being far smaller than an open trench, bore pits are still excavations, and they come with their own planning, sizing, and safety requirements.
Entry Pits vs. Exit Pits
Entry and exit pits serve related but distinct roles on a bore, and each is typically sized and positioned differently.
| Factor | Entry Pit | Exit Pit |
|---|---|---|
| Primary function | Rig setup and drill string entry | Pilot bore breakout and pullback staging |
| Typical location | Near the drill rig | Opposite end of the crossing |
| Key consideration | Entry angle, rig footprint | Pipe staging space, breakout clearance |
| Fluid management | Fluid pumping and circulation | Fluid return and containment |
On longer crossings, both pits also serve as monitoring points where crews confirm the drill head is tracking correctly and that drilling fluid is circulating as expected.
How Bore Pits Are Planned and Sized
Bore pit dimensions aren't guesswork. A few factors typically drive the plan for each pit:
Entry angle and rig requirements. The entry pit has to accommodate the drill rig's angle of approach, which is usually somewhere between 8 and 20 degrees. Too shallow a pit, and the rig can't achieve the correct entry angle; too large, and crews are excavating more than the project needs.
Pipe or conduit dimensions. The exit pit needs enough length and depth to stage the product pipe and allow it to be connected to the drill string without excessive bending or stress on the pipe.
Soil conditions. Loose or saturated soils often require larger pits, sloped sides, or shoring to remain stable, while firmer soils may allow a tighter footprint.
Utility clearance. Both pits are positioned only after existing utilities in the area have been located and, where necessary, physically exposed through potholing, so the pit itself doesn't create a new conflict.
Fluid containment needs. Pits are often designed with enough capacity to manage returning drilling fluid, particularly on the entry side, to reduce the risk of it spreading beyond the work area.
For a look at the equipment that operates from these pits during a bore, see our guide to directional boring equipment.
Safety Considerations for Bore Pits
Because bore pits are excavations, they carry the same fundamental risks as any other dug opening, and they're subject to excavation safety standards even though they're often smaller and shorter-lived than a trench. Key safety practices include:
- Protective systems for deeper pits. Sloping, benching, or shoring may be required depending on depth and soil type, consistent with OSHA excavation safety standards.
- Barricading and signage. Open pits near roadways, sidewalks, or public areas need clear physical protection to prevent accidental entry.
- Utility verification before digging. Locating and potholing happen before pit excavation begins, not after, so crews know exactly what's beneath the surface.
- Fluid and spoil management. Drilling fluid and excavated soil are contained and handled according to site and environmental requirements, particularly on pits located near waterways or sensitive areas.
Experienced crews treat bore pit excavation with the same discipline as any other dig, because a poorly planned pit can compromise the safety and success of the entire bore that follows.
Why Bore Pit Planning Affects the Whole Project
A well-planned bore pit does more than give the rig somewhere to sit. Correct sizing and positioning reduce the risk of entry angle problems, fluid containment issues, and pipe handling complications during pullback, all of which can slow down or compromise a crossing. On projects involving horizontal drilling or larger HDD pipeline crossings, pit planning is worked out during route and bore path engineering, well before equipment mobilizes to the site.
Frequently Asked Questions
How deep are bore pits? Depth depends on the entry angle, pipe diameter, and soil conditions, but most bore pits range from a few feet to around 6 to 8 feet deep. Larger pipeline crossings may require deeper or larger pits to accommodate rig setup and pipe handling.
Do bore pits require shoring? Shoring or sloping may be required depending on pit depth and soil stability, in line with OSHA excavation requirements. Shallow, stable-soil pits often don't require shoring, while deeper pits typically do.
How long does it take to prepare a bore pit? Preparation time varies with pit size and soil conditions, but most entry and exit pits can be excavated and prepared in a matter of hours once utility locating and site prep are complete.
Are entry and exit pits the same size? Not usually. Entry pits are sized around the drill rig's setup and entry angle, while exit pits are often sized to accommodate staging and connecting the product pipe, which can require more length depending on pipe diameter.
Work With a Crew That Plans Every Stage of the Bore
Bore pits might look like a small part of a directional boring project, but proper planning here sets up everything that follows. PL-Enerserv's crews plan and prepare entry and exit pits as part of every directional boring and HDD project we deliver across the Northeast, Midwest, and Southeast.
If you have a project that calls for directional boring, contact us to talk through your route, soil conditions, and site requirements, or explore our full range of pipeline services.