Bore Path Planning

What a Bore Plan Contains

A usable bore plan is more than a line on a route map. It carries the alignment in plan view, a depth profile along the shot, staked entry and exit locations, cover requirements by segment, every known conflict with its measured depth and offset, and the pit layouts at each end.

It also carries the constraints that will actually stop the work: permit conditions, required work windows, facility owner standby requirements, and any restriction on where equipment can be staged. A plan that ignores those is a drawing, not a plan.

The point of putting it on paper is to have the argument before the crew is on site. Every disagreement about depth, clearance, or exit location is cheap to resolve in the office and expensive to resolve with a rig running and a lane closed.

Building the Profile Around Known Conflicts

The profile is built from the ground up, starting with what has been located and exposed. Each conflict gets an actual depth, and the bore is routed under or over it with clearance that exceeds the owner minimum, so ordinary variation during drilling does not eat the margin.

Grade is the second input. Cover requirements are measured from the lowest surface above the bore, so ditch inverts, swales, culverts, and drainage structures set the controlling depth rather than the road crown. A profile drawn against pavement elevation alone will come up shallow somewhere.

Soil is the third. Where sand, muck, or shell layers are expected, the profile is set to reach material that will hold an open hole and to avoid daylighting through a soft zone. On water and wetland approaches, that usually means carrying more depth than the permit strictly requires.

Bend Radius and Product Limits

Every profile change has a radius, and two separate limits apply. The drill rod has a bend radius it can tolerate without fatigue, and the product being installed has its own, usually tighter, minimum. Conduit and cable have to survive being pulled through whatever shape the pilot created.

Planning against the product limit is what prevents damage that is invisible until the fiber is tested. A profile that corrects sharply to clear a conflict can pass a mandrel and still put unacceptable stress on cable during pullback, or leave a duct with a permanent ovality at the bend.

So corrections get spread. Where the bore needs to move, the deviation begins earlier and is resolved over a longer run, which increases shot length slightly and removes a category of failure entirely.

Choosing Entry and Exit Points

Entry and exit selection controls whether the required cover is achievable. A pit set too close to the crossing forces a steep launch angle that either misses cover under the pavement or exceeds bend radius trying to level out. Setting back further costs footage and solves both problems.

Site constraints then narrow the options: right of way width, clear zone limits, drainage structures, driveways, mature trees, overhead conductors above the rig, and where equipment can legally sit during the shift. Exit points on private property need permission arranged in advance, not negotiated with the drill running.

Where a route has handholes, vaults, or splice points planned, pits are placed to serve double duty at those locations so the same excavation supports the structure placement instead of opening the ground twice.

Feeding the Permit Package

Permit reviewers want to see a specific set of things: where the crossing is, how deep it will be, what it passes and by how much, where the pits sit relative to the right of way, and how traffic will be handled. A bore plan built with those questions in mind moves through review faster than one that has to be supplemented twice.

It also protects the schedule after approval. When a permit comes back with a modified condition, having a real profile means the change can be evaluated immediately, and you can be told whether it costs an hour or a week.

The same plan becomes the baseline for the as-built. Deviations made in the field are recorded against it with the reason, so the closeout package shows what was intended, what was actually built, and why they differ.

Keeping one document across permitting, construction, and closeout also removes the version problem. Reviewers, crews, and your engineering team work from the same alignment and the same conflict list, so a change made in one place does not quietly leave the other two working from something older.

What Data Do You Need Before Planning a Bore?

Good plans start with good inputs. The minimum set is the route design, Sunshine 811 locate results, available as-builts from utility owners, and the permit conditions, or the agency's published standards if the permit is not yet issued. Grade information matters too, whether it comes from a survey, design plans, or field measurements at ditch inverts and drainage structures.

Field data fills the gaps. A site walk shows what no drawing does: new driveways, fences, trees, signs, valve boxes, meter cans, and signs of private lines. Potholes add measured depth at each conflict. A plan is only as good as the field work behind it, which is why the walk and the exposure work are part of planning, not a separate task.

When inputs are missing, the plan says so. A segment with no records and no exposure is marked as unknown, with a plan to investigate before drilling, instead of being drawn as clear.

• Route design and conduit configuration
• Sunshine 811 locate results and owner records
• Prior as-builts for the corridor
• Permit conditions or published agency standards
• Grade at ditch inverts, culverts, and structures
• Site walk notes and pothole measurements

When Should a Bore Plan Change After It Is Issued?

A bore plan is a working document. It should change when the field differs from what it assumed: a conflict deeper or shallower than expected, a new obstruction at a pit location, a permit condition that moves a crossing, or ground that behaves differently during the pilot.

Changes follow a simple rule. The crew does not improvise a new profile around a surprise. The issue is reported, the profile is revised against the same limits for cover, clearance, and bend radius, and the change is recorded with its reason. Small adjustments can be made the same day. Larger ones may need the permit authority or facility owner to agree first.

This is what keeps the as-built honest. The final record shows the plan, the change, and why it was made, so anyone reading it later understands the bore that is actually in the ground.