Horizontal Directional Boring (HDD) SWMS

Horizontal Directional Drilling (HDD) is a trenchless construction method used to install conduits, water mains, gas pipes and electrical cables beneath roads, waterways and existing infrastructure without open-cut excavation. The work involves launching a steerable drill head from an entry pit, tracking it via walkover locator to an exit pit, then back-reaming and pulling product through the bore. HDD is classified as High Risk Construction Work under WHS Regulation 2025 section 291 because operations routinely occur in proximity to energised electrical services, pressurised gas mains and live water reticulation, with pressurised drilling fluid (bentonite slurry) typically circulated at 700–2000 kPa. A documented Safe Work Method Statement is mandatory before any HDD activity commences, must be developed in consultation with the drill crew, locator operator and pit hands, and must remain available on site for the duration of the works. This SWMS addresses pit excavation, rig setup, strike prevention, fluid management and emergency response.

Hazards identified

7 hazards covered, sorted by priority.

Control measures

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

1. 1Elimination — Where alignment permits, relocate the bore path to avoid corridors containing high-voltage cable, high-pressure gas or asbestos cement water mains identified during DBYD planning.
2. 2Elimination — Prohibit any person from standing within the 8-metre electrical exclusion zone around the rig, drill string and locator during pilot bore through known services corridor.
3. 3Substitution — Replace dry-mix bentonite powder with pre-hydrated liquid polymer slurry to eliminate respirable dust generation during fluid system charging and recirculation.
4. 4Engineering — Use a calibrated walkover locator with depth and datalogging, verify pilot head position every 3 metres, and potholing by hydro-excavation at every service crossing prior to bore.
5. 5Engineering — Fit the rig with strike alert system, insulating mats under operator station, equipotential bonding of drill frame to earth grid, and emergency rotation kill switch within operator reach.
6. 6Engineering — Install trench shields or benching to AS 5047 in entry and exit pits exceeding 1.5 metres depth, with rigid access ladder extending 1 metre above pit lip.
7. 7Administrative — Hold a documented pre-start briefing using this SWMS, confirm DBYD plans less than 28 days old, verify asset owner stand-over for HV and gas crossings per AS/NZS 7000.
8. 8Administrative — Establish frac-out response procedure with spill kits, silt fence, vac truck on standby, downstream stormwater isolation and EPA notification trigger at 20-litre release threshold.
9. 9PPE — Class 00 electrical insulating gloves rated 500V AC with leather overgloves for any rod handling, dielectric safety boots to AS/NZS 2210.3 and arc-rated long-sleeve coveralls.
10. 10PPE — P2 respiratory protection during dry bentonite handling, chemical splash goggles, hi-vis Class D/N garments to AS/NZS 4602.1 and hearing protection to SLC80 Class 4 within 7 metres of rig.

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

On a suburban telecommunications conduit installation requiring a 95-metre bore beneath a four-lane arterial road, the site supervisor opens the pre-start meeting by walking the four-person crew through this SWMS at the entry pit. The locator operator confirms DBYD plans are 11 days old and identifies a 110 kV cable and a medium-pressure gas main intersecting the planned alignment. Referring to the hazard register, the crew agrees to hydro-excavate three potholes to physically verify both services before the pilot head approaches the 8-metre exclusion zone. The rig operator signs on, acknowledging the strike alert system test, insulating mat condition and emergency kill switch function recorded in the SWMS verification block. Mid-bore, the locator reports unexpected slurry pressure rise from 1100 to 1850 kPa. The supervisor consults the frac-out response control on page three, halts rotation, deploys the silt fence around a nearby stormwater pit, and dispatches the pit hand to inspect the road surface. A minor surface return is contained with the spill kit, vac truck removes 60 litres of slurry, and the EPA notification threshold is logged. Work resumes after fluid viscosity is adjusted and the bore path reverified, with the supervisor amending the SWMS daily diary to capture the corrective action and re-briefing the crew before continuing back-ream.

Related legislation

• WHS Act 2011 (model)
• WHS Regulation 2025
• Code of Practice — Hazardous Manual Tasks

Frequently asked questions