Underground Water, Sewer, Gas and Fire Line Installation by HDD

Horizontal directional drilling installs a pipe or duct beneath a finished surface from two small pits, which is why it suits occupied buildings, paved courtyards and roads that cannot be closed. What decides whether a given run is borable is not its length but its ground, its available pit positions and what is already buried along the path — and the third of those is the one clients most often have no record of.

What decides whether a run can be bored

Pit positions come first: a bore needs level standing space at both ends, and inside a built site that is frequently the binding constraint rather than the drilling itself. Ground comes second, since boulder or rubble fill common on older sites can stop a pilot bore. Existing services come third, and on a brownfield site they are established by GPR scan rather than assumed, because a strike inside an occupied property is a considerably worse event than one on an open road.

What you receive at handover

A coordinate-tied as-built drawing showing the line laid, its depth and its route, which most properties have never had. Pressure or flow test records appropriate to the line type, documented rather than merely performed — on fire lines these form part of the compliance record the authority will ask for. Reinstatement photographed before and after where any surface was opened. Municipal permission and restoration closure documents where a public road was crossed, with the deposit pursued to release rather than left standing against the applicant.

Beyond the basics

Is HDD more expensive than trenching? Per metre, usually. Once reinstatement of a paved surface, disruption to residents and the risk of a poor restoration are counted, it is frequently cheaper on a finished site.

How much space do the pits need? Less than most clients expect, but they need level ground at both ends. On constrained sites pit position is the binding constraint rather than the bore itself.

Can you bore under an existing building? Under driveways, courtyards, roads and landscaping, routinely. Under a structure itself is a different question that depends on foundations and is assessed case by case.

What if you hit something unexpected? We stop and reassess rather than forcing progress. On an occupied site forcing a bore through unknown ground risks a strike that costs far more than the pause.

Do you scan before boring? On brownfield sites, yes, and we recommend it strongly. It costs a fraction of the strike it prevents and is the single step that most reliably keeps a job moving.

Terms used on this page

HDD — horizontal directional drilling, installing a line beneath a surface from two small pits. Entry and exit pit — the small excavations at each end of a bore, the only surface disturbance required. Cover — the depth of material over a laid line, specified by the authority rather than by convenience. Fire NOC — the fire authority's no-objection certificate, frequently the last item before occupancy. As-built — a record of what was actually installed and where, which most properties do not have.