Tunnelling Occupational Hygiene

Tunnel boring machines, road headers, drill-and-blast operations, and shotcrete application in quartz-bearing rock generate sustained RCS exposure for face workers. The WES of 0.05 mg/m³ is frequently approached or exceeded without effective ventilation and dust suppression. Geology determines silica content — sandstone tunnels produce near-pure quartz dust.

Underground loaders, haul trucks, agitator trucks, shotcrete rigs, and generators produce diesel exhaust in a confined underground atmosphere. The new WEL of 0.01 mg/m³ elemental carbon (effective December 2026) will require most tunnel projects to transition to electric or hybrid vehicles and improve ventilation capacity. Current monitoring uses elemental carbon (EC) and total carbon (TC) analysis.

Tunnel boring machine operation, ventilation fan noise, shotcrete spraying, and vehicle movement in a reverberant underground space create complex noise fields that frequently exceed 100 dB(A). Shift workers in 12-hour underground rotations may accumulate noise doses well above the WES of 85 dB(A) LAeq,8h.

Underground ventilation system performance determines air quality for all contaminants. Ventilation assessments measure airflow velocity, volume, and distribution throughout the tunnel to confirm that fresh air supply meets legislative requirements. Real-time monitoring for oxygen, carbon monoxide, nitrogen dioxide, and hydrogen sulphide provides continuous atmospheric safety verification.

Typical Worker Groups

Common similar exposure groups (SEGs) assessed for this sub-category.

Regulatory Context

Tunnel construction in NSW is regulated under the WHS Act and Regulation with additional guidance from SafeWork NSW. The Tunnelling Code of Practice (Safe Work Australia) addresses ventilation requirements, atmospheric monitoring, emergency procedures, and health monitoring. Mandatory health monitoring includes respiratory function testing for RCS exposure and audiometric testing for noise exposure. The WEL for DPM (0.01 mg/m³ EC from December 2026) will require tunnel projects to demonstrate compliance through systematic personal and area monitoring programmes.