Directional Drilling (HDD) SWMS

Horizontal Directional Drilling (HDD) is a trenchless method used to install utilities — gas, water, electrical, telecommunications and sewer — beneath roads, waterways and existing infrastructure. The work involves launching a steerable pilot bore from an entry pit, tracking the drill head with walkover or wireline locators, pre-reaming the bore to required diameter, and pulling product pipe back through the void using bentonite drilling fluid as a lubricant and cuttings carrier. Under the Model WHS Regulations Chapter 4 Part 4.5, HDD plant is registrable powered mobile plant requiring documented risk control, and the work routinely intersects multiple High Risk Construction Work categories under section 291 — including work near energised underground services, excavation deeper than 1.5 m at entry/exit pits, and operation of powered mobile plant adjacent to workers on foot. A Safe Work Method Statement is mandatory before HDD commences and must be reviewed at every shift change, service-strike near-miss, or change to bore-path geometry.

Hazards identified

7 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1Elimination — Where feasible, relocate bore path to avoid known service corridors entirely by redesigning alignment during the DBYD planning phase before mobilisation.
2. 2Elimination — Hand-expose (potholing) all services within 500 mm of the planned bore path using vacuum excavation to eliminate strike uncertainty before drilling commences.
3. 3Substitution — Substitute conductive steel drill rods with non-conductive fibreglass-rod systems when boring within 3 m of known live HV cables per ENA NENS 04 guidance.
4. 4Engineering — Install voltage-detection strike alert systems on the drill rig frame and remote locator wand with audible alarm thresholds set per manufacturer specification.
5. 5Engineering — Use guarded breakout wrench stations with interlocked rotation cut-off compliant with AS/NZS 4024.1601 to prevent rod-joint entanglement during make/break.
6. 6Engineering — Bund and contain mud-recycler and entry pit with sandbags, silt socks and frac-out monitoring points along the bore alignment at 10 m intervals.
7. 7Administrative — Conduct daily pre-start brief using this SWMS, verify current DBYD plans (less than 28 days old) and complete a documented service-proving checklist before each bore.
8. 8Administrative — Establish exclusion zones with physical barriers around drill rig swing radius and pullback alignment; only designated locator and pit attendant permitted inside.
9. 9Administrative — Implement a stop-work trigger any time tracker signal is lost, drill fluid pressure spikes unexpectedly, or visible frac-out occurs — escalate to supervisor before resuming.
10. 10PPE — Mandatory Class 5 hi-vis, AS/NZS 1801 hard hat, AS/NZS 1337 impact eyewear, dielectric Class 00 gloves at rig controls, and 4-gas personal monitors for pit entrants.

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

On a suburban arterial road upgrade involving a 180 m gas-main installation under a four-lane carriageway, the HDD crew assembles at the entry pit for the morning pre-start brief. The site supervisor opens this SWMS on a ruggedised tablet and walks the four-person crew — driller, locator, pit attendant and trafficker — through each hazard line. The crew confirms the DBYD plans were re-pulled 11 days ago and that a 132 kV HV electrical feeder runs 1.8 m offset and 1.2 m above the planned bore at chainage 65 m. The supervisor selects the dielectric drill-rod substitution control and the strike-alert engineering control from this SWMS, and the driller confirms the fibreglass rods are loaded. Each worker signs on against the document, recording their name, role and competency. Mid-shift, the locator loses tracker signal at chainage 60 m. Referring back to the SWMS stop-work trigger, the driller halts rotation immediately, the crew reconvenes, and they re-verify the tracker battery and offset before resuming. The frac-out monitoring control prompts a visual sweep of the gutter line, where a small bentonite seepage is found at chainage 72 m — the supervisor escalates per the SWMS, deploys silt socks, and amends the document with the new control before drilling continues.

Related legislation

• WHS Act 2011 (model)
• WHS Regulation 2025
• AS 2550 — Cranes, hoists and winches; AS 1418 series

Frequently asked questions