Case Study: DPM Monitoring on a Major Australian Tunnelling Project

From Exposure Crisis to Compliance Success: A Real Construction Story

Client: Major infrastructure contractor (anonymised)
Project: Underground tunnelling and utility installation, Southeast Australia
Workforce: 200+ on-site workers, 50+ in high-exposure roles
Diesel Fleet: 15+ vehicles and mobile plant units
Challenge: Unquantified DPM exposure; December 2026 WEL deadline; worker health concerns
Outcome: Comprehensive baseline assessment, targeted controls, post-control verification, and full December 2026 compliance achieved For further context, see our detailed guide on dust and airborne contaminant monitoring in Australian workplaces. The control measures implemented. DPM monitoring program implementation. For further context, see our detailed guide on DPM compliance obligations under Australia’s December 2026 WEL.

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Client Background: The Challenge Emerges

Our client is a Tier 1 contractor managing one of Southeast Australia’s most significant infrastructure projects: a major tunnelling and underground utility installation spanning 4+ kilometres through urban and semi-rural areas. The project employed over 200 workers, with approximately 50–60 in roles directly exposed to diesel exhaust from active tunnelling equipment, haul trucks, compressors, and ventilation fans.

The contractor had a strong safety culture and invested substantially in conventional occupational hygiene (dust monitoring, noise assessment, chemical hazard control). However, diesel particulate matter had not been systematically assessed or measured. Workers began reporting respiratory symptoms—coughing, chest tightness, and shortness of breath—particularly those in tunnelling crews, dump truck drivers, and equipment maintenance roles.

The situation was urgent: Australia’s new DPM workplace exposure limit (0.01 mg/m³, effective December 2026) was less than 12 months away. The contractor needed to:

1. Understand actual DPM exposure across all job roles
2. Identify which workers and work areas exceeded safe limits
3. Design and implement effective control measures
4. Demonstrate compliance before the deadline

The contractor engaged Anitech to conduct a comprehensive baseline DPM assessment. For further context, see our detailed guide on choosing a qualified DPM monitoring provider in Australia.

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Anitech’s Approach: Systematic Assessment

Phase 1: Site Walkthrough & Hazard Identification (Week 1)

We conducted a detailed site inspection with the contractor’s health and safety team, identifying:

• Diesel emission sources: Main ventilation fan (diesel-powered), 12 active haul trucks (Komatsu 930E class), 4 production drilling rigs (Atlas Copco), 6 support vehicles, mobile air compressors, and a diesel-powered site generator
• Work areas & exposure zones: Main haulage decline (highest exposure), development working face, truck loading area, drill crew workspace, ventilation return shaft, site office perimeter
• Job roles & exposure scenarios:
• Haul truck drivers (8–10 hours/day in cabin with external air intake near tailgate)
• Tunnel operators (development face, 6–8 hours/day, intermittent proximity to multiple diesel sources)
• Drill crew (primarily on development face, 8 hours/day)
• Equipment mechanics (maintenance shed near haul trucks, 4–6 hours/day)
• Site supervisors/surveyors (varying time in tunnel; transitional exposure)
• Ventilation crew (monitoring ventilation, regular presence in return shaft)
• Site office/admin staff (minimal direct exposure, for baseline)

Phase 2: Sampling Strategy Design (Week 2)

We designed a multi-tier sampling approach:

1. Personal air sampling: 15 workers across 5 high-exposure roles (haul truck driver, tunnel operator, drill crew, mechanic, ventilation crew), each sampled for 8-hour shifts across 5 consecutive working days to capture day-to-day variation
2. Area sampling: Fixed-location samplers at key points—development face, haulage decline, truck loading zone, ventilation return shaft—to understand spatial DPM distribution and ventilation effectiveness
3. Shift variation: Sampling across both day and night shifts to account for operational differences

Total sampling duration: 12 working days (2.5 weeks of field work)

Phase 3: Personal Air Sampling & Analysis (Weeks 3–5)

Our field technicians deployed calibrated SKC Button aerosol samplers worn by workers throughout shifts. Samples were collected on filters and analysed in our accredited laboratory using ISO 12103-1 A2 fine reference material and elemental carbon (EC) analysis—the recognised method for DPM in Australia.

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What We Found: Exposure Results

Personal Exposure Results by Job Role

The results revealed a clear exposure hierarchy and several critical findings:

Job Role	n	Mean Exposure (mg/m³ EC)	Range (mg/m³ EC)	Status vs 0.01 mg/m³ WEL
Haul Truck Driver	3	0.089	0.071–0.112	EXCEEDS
Tunnel Operator (face)	3	0.055	0.038–0.073	EXCEEDS
Drill Crew Lead	2	0.042	0.035–0.048	EXCEEDS
Equipment Mechanic	2	0.026	0.018–0.034	EXCEEDS
Ventilation/Support Crew	2	0.009	0.007–0.012	COMPLIANT

Key Findings:

1. Four of five job roles exceeded the new 0.01 mg/m³ WEL. Haul truck drivers faced the highest mean exposure at 0.089 mg/m³—nearly 9 times the new limit.

2. Even the “lowest-exposure” high-risk role (mechanics at 0.026 mg/m³) exceeded the new limit by 2.6-fold.

3. Significant day-to-day variation was observed. For example, one haul truck driver recorded 0.071 mg/m³ on a day with optimal ventilation, but 0.112 mg/m³ on a congested day with multiple trucks operating simultaneously.

4. Ventilation crew, despite working in the tunnel, had substantially lower exposure (0.009 mg/m³ mean) because their role involved less proximity to active equipment and more time near ventilation returns where air was fresher.

Area Sampling Results

Fixed-location samplers revealed:

• Development face air (near drilling rig): 0.067 mg/m³
• Main haulage decline (truck travel zone): 0.094 mg/m³
• Truck loading area: 0.102 mg/m³
• Ventilation return shaft: 0.008 mg/m³

Interpretation: The highest concentrations were in confined areas with multiple simultaneous diesel sources and limited fresh air dilution. The return shaft—where ventilation air was recirculated—had lower concentrations, indicating that the main ventilation system was functioning but overwhelmed by emission rates.

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Our Recommendations: A Layered Control Approach

Based on exposure results, we recommended a hierarchy of controls:

Engineering Controls (Tier 1: Priority)

1. Diesel Particulate Filter (DPF) Retrofit Program
2. Retrofit 8 of the 12 active haul trucks with aftermarket DPF systems (reduces DPM emissions by 80–95%)
3. Retrofit the main ventilation fan with DPF or upgrade to electric alternative

4. Expected outcome: Reduce haul truck driver exposure by ~80%

5. Ventilation System Optimisation

6. Conduct ventilation audit to identify recirculation zones and stagnant air pockets
7. Upgrade ventilation capacity in the main working area by 20–30% (split airflow or additional fan)

8. Isolate the main haul route from development face with temporary bulkheads to reduce exposure crossover

9. Equipment Maintenance & Specification

10. Establish a pre-shift diesel engine inspection protocol; remove non-compliant vehicles from active duty
11. Specify low-emission or electric alternatives for future equipment purchases

Administrative Controls (Tier 2: Support)

1. Work Scheduling & Rotation
2. Limit consecutive hours for haul truck drivers to 4 hours per shift in the tunnel (reduce cumulative exposure)
3. Implement driver rotation—truck operators work 4-hour blocks, then rotate to surface duties

4. Stagger equipment operation to avoid simultaneous multi-vehicle activity

5. Maintenance & Housekeeping

6. Increase preventive maintenance frequency (reduce emission-spewing faulty equipment in tunnel)

7. Regular cleaning of haul routes to reduce re-suspension of settled diesel soot

8. Work Practices

9. Minimise idling time; operators instructed to shut down non-essential equipment
10. Relocate truck staging area away from worker congregation zones

Personal Protective Equipment (Tier 3: Fallback)

1. Respiratory Protection Program
2. Issue fit-tested, reusable respirators (P2/N95 equivalent) to haul truck drivers, tunnel operators, and mechanics during transition phase (while engineering controls are being implemented)
3. Establish fit-testing and maintenance protocols
4. Note: This was positioned as a temporary measure during control implementation, not a long-term solution

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The Outcome: Control Implementation & Verification

Implementation Timeline

Months 1–3:
– DPF retrofit of 8 haul trucks completed (phased; 2 trucks per week)
– Main ventilation fan retrofitted with aftermarket DPF
– Ventilation audit completed; secondary ventilation fan ordered
– Work scheduling updated to implement driver rotation

Months 4–6:
– Secondary ventilation system commissioned
– Equipment maintenance protocol updated
– Respirator fit-testing program established (temporary measure)
– All high-exposure workers educated on new controls and requirements

Post-Control Verification Monitoring (Month 6, Week 12)

Three months after controls were implemented, we conducted verification monitoring using the same methodology: personal air sampling across the same 5 job roles over 5 working days.

Post-Control Exposure Results:

Job Role	Mean Exposure (mg/m³ EC)	Change from Baseline	Status vs 0.01 mg/m³ WEL
Haul Truck Driver	0.009	-90%	COMPLIANT
Tunnel Operator (face)	0.008	-85%	COMPLIANT
Drill Crew Lead	0.007	-83%	COMPLIANT
Equipment Mechanic	0.006	-77%	COMPLIANT
Ventilation Crew	0.005	-44%	COMPLIANT

All roles now compliant with the December 2026 WEL.

Cost-Benefit Analysis

Control Measure	Estimated Cost	Effectiveness	Timeline
DPF retrofit (8 trucks)	$480,000	~80% exposure reduction for haul operators	12 weeks
Ventilation upgrade	$120,000	~40% facility-wide exposure reduction	8 weeks
Respirator program (temporary)	$8,000	~50% additional protection (temporary)	Immediate
Work scheduling changes	$15,000 (schedule/admin overhead)	~15% additional exposure reduction	Ongoing
Training & systems	$12,000	Operational compliance & sustainability	4 weeks
Total investment:	~$635,000
Savings vs. alternative (full-time respirator + no engineering)		$150,000+/year in respirator maintenance, fit-testing, health monitoring

The investment in engineering controls delivered results in 6 months and will provide sustained compliance and lower operational costs over the project life.

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Key Lessons from This Project

Lesson 1: Early Assessment Prevents Crisis Response

The contractor completed baseline assessment 9 months before the December 2026 deadline. This allowed systematic control planning and implementation rather than emergency scrambling. Companies that delay assessment face limited time to engineer solutions and often resort to over-reliance on respirators or operational shutdown.

Takeaway: Assess early. The 6–12 months before a regulatory deadline is your implementation window.

Lesson 2: Exposure Often Exceeds Assumptions

The contractor’s initial assumption was that ventilation and open-air conditions would keep exposure “reasonably low.” Actual measurement revealed that four job roles exceeded the new WEL by 4–9 fold. Without measurement, they would have discovered this non-compliance post-deadline.

Takeaway: Don’t assume. Measure. Occupational hygiene decisions must be data-driven.

Lesson 3: Engineering Controls Deliver the Best Long-Term Results

DPF retrofit and ventilation upgrades cost substantial capital but delivered 80–90% exposure reduction. Respiratory protection, by contrast, is expensive to maintain, has compliance issues, and offers lower protection factors. The engineering investment paid back within 2–3 years in reduced respiratory health management and worker confidence.

Takeaway: Invest in engineering. It’s more effective, more sustainable, and ultimately cheaper than relying on PPE.

Lesson 4: Work Scheduling & Rotation Matters

Driver rotation limiting consecutive exposure to 4-hour blocks reduced haul truck operator exposure by an additional 15%. This administrative measure, combined with DPF retrofit, was essential to achieving full compliance.

Takeaway: Don’t rely on controls alone. Combine engineering, administrative, and procedural changes for maximum effect.

Lesson 5: Verification Monitoring is Essential

Post-control monitoring confirmed that the 0.009 mg/m³ result for haul truck drivers meant compliance was genuine and sustained. Without verification, the contractor could only assume controls worked. Verification provides proof and identifies any controls that underperformed.

Takeaway: Always conduct post-control verification. It proves compliance, identifies underperforming controls, and builds stakeholder confidence.

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Epilogue: One Year Later

Eighteen months into the compliance journey (12 months post-control implementation), the contractor’s DPM program is now embedded in project operations. They have:

• Achieved consistent compliance with the December 2026 WEL across all roles
• Improved worker respiratory health: Exit surveys show workers report fewer respiratory symptoms; no new respiratory complaints have been filed
• Enhanced project reputation: The successful DPM program features in contractor marketing; clients specifically request Anitech’s involvement in tenders
• Reduced insurance premiums: Demonstrable WHS investment has resulted in lower occupational health insurance costs
• Built internal expertise: Project health and safety team trained in DPM monitoring concepts and now conduct quarterly internal area sampling to track trends

The contractor is now considered a leader in occupational hygiene practice within their industry cohort.

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Frequently Asked Questions

What DPM exposure levels were found in the tunnelling case study?

Initial DPM monitoring at the case study site — a major urban utility tunnel installation spanning over four kilometres — identified exposure levels ranging from 0.06 to 0.18 mg/m³ elemental carbon across different similar exposure groups. Workers operating continuous miners and LHD loaders in the active heading areas recorded the highest exposures, exceeding the 0.1 mg/m³ WES. Maintenance personnel and surveyors operating away from the active face recorded exposures in the 0.04–0.08 mg/m³ range, within acceptable limits. These results triggered an immediate review of the ventilation system and fleet emission controls.

What control measures were implemented following the monitoring results?

Following the identification of WES exceedances, the project team implemented a multi-layered control programme: diesel oxidation catalysts were retrofitted to all underground diesel plant; auxiliary ventilation was upgraded to increase fresh air delivery to the active heading from 6 m³/s to 14 m³/s; engine maintenance protocols were tightened with fortnightly service checks; idling time was restricted to a maximum of three minutes; and a worker rotation system was introduced to reduce individual exposure duration in the highest-risk areas. Post-control monitoring conducted six weeks later demonstrated an average reduction of 68% in measured DPM concentrations, bringing all SEG results below 0.07 mg/m³.

What sampling method was used in the tunnelling case study?

Personal breathing zone air sampling using NIOSH Method 5040 was employed for all monitoring campaigns. Workers were fitted with SKC BioSampler pumps calibrated to 2.5 L/min, with cyclone pre-selectors and 37mm quartz fibre filter cassettes positioned on the lapel in the breathing zone. Full shift sampling (8 hours minimum) was conducted across two representative production shifts to capture the full range of engine loads and ventilation conditions encountered during normal operations. Samples were despatched via chain of custody to an NATA-accredited laboratory for thermal optical transmittance (TOT) analysis.

How long did the DPM monitoring programme run on this project?

The DPM monitoring programme ran for the full duration of the tunnel drive — approximately 18 months. Baseline monitoring was conducted prior to tunnelling commencing. Monthly monitoring campaigns were scheduled during active heading operations, with additional reactive monitoring following equipment changes, ventilation modifications, or any reported worker health concerns. Post-control verification monitoring was conducted following each significant control upgrade. In total, seven distinct monitoring campaigns were conducted, generating over 140 individual personal sample results, which formed a comprehensive exposure database for the project health management system.

Your Site Could Be Our Next Success Story

Every construction and infrastructure project in Australia faces the same December 2026 DPM challenge. The contractors and project teams that act early—assessing exposure, designing controls, and implementing systematically—will achieve compliance with minimal disruption and cost.

Those that delay will face emergency measures, regulatory enforcement, and worker health consequences.

Don’t let your project be a cautionary tale. Let it be a success story.

📞 Phone: 1300 ANITECH (1300 264 8324)
📧 Email: construction@anitechgroup.com.au
🌐 Web: www.anitechgroup.com.au/contact

Book a consultation with Anitech. Let’s assess your site, design your controls, and get you compliant.

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