SWMS template · Confined Spaces
Storage Tank Cleaning — Safe Work Method Statement
Safe Work Method Statement for the internal cleaning of above-ground and below-ground storage tanks containing residual hydrocarbons, chemicals, or potable water, including degassing, sludge removal, and surface preparation.
Last reviewed
- Category
- Confined Spaces
- HRCW
- 2 categories
- Job steps
- 5
- Hazards rated
- 7
- PPE items
- 8
Storage tank cleaning — whether for above-ground petroleum storage tanks, underground fuel tanks, chemical storage vessels, or potable water reservoirs — is classified as confined space work under the model WHS Regulations and requires a confined space entry permit, atmospheric testing, full energy and process isolation, and a documented rescue plan before any worker enters. This is among the highest-risk categories of confined space work due to the toxic and flammable residues typically present.
Hydrocarbon storage tanks present a dual hazard: the atmosphere within may be oxygen-deficient and may contain petroleum vapours above the lower explosive limit (LEL), creating both an asphyxiation risk and an explosion risk. Degassing — the forced ventilation of the tank to below 1% LEL before entry — is mandatory and must be verified by continuous gas monitoring before the entry permit is issued. The degassing process itself must use intrinsically safe fans and ventilation equipment, as any ignition source in a vapour-laden atmosphere can cause a catastrophic explosion. API Standard 2015 (Requirements for Safe Entry and Cleaning of Petroleum Storage Tanks) provides internationally recognised guidance that complements the Australian WHS Regulations for petroleum tank cleaning.
Sludge removal from the base of hydrocarbon tanks is particularly hazardous because agitation of the sludge releases additional vapours into the atmosphere. Workers must use supplied air or SCBA where the atmosphere cannot be maintained below 5% LEL, and hot work of any kind — including spark-producing tools — is absolutely prohibited until the tank has been gas-freed and tested to confirm a safe atmosphere. Chemical tanks require a full review of the previous contents' SDS to identify specific toxic, corrosive, or reactive hazards.
Customise this template with the tank identifier and prior contents, the degassing method and ventilation rate, the gas testing instrument and calibration record, the isolation blinds or blanks fitted, the sludge disposal method and environmental approvals, and the name and qualifications of the confined space entry supervisor who issues the permit.
This SWMS is applicable in all Australian states and territories. Environmental approvals for sludge and washwater disposal must be obtained from the relevant state EPA before work commences.
Important: This SWMS template is a starting point only. Review and customise it for your workplace and task. The PCBU remains responsible for ensuring the SWMS is suitable for the work. Not legal advice.
High Risk Construction Work Types
- Work in or near a confined space
- Work in an area that may have a contaminated or flammable atmosphere
Personal Protective Equipment
- Supplied-air respirator (SAR) with escape set
- Full-body chemical-resistant coveralls (Type 3 or 4)
- Chemical-resistant gloves (double-glove for hydrocarbon tanks)
- Safety harness and retrieval lanyard
- Chemical-resistant safety boots
- Safety helmet
- Chemical splash goggles
- Intrinsically safe torch and lighting
Risk Assessment
RatingsCatastrophicHighModerateLow
Step 1Tank Degassing and Preparation
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Explosion from ignition of hydrocarbon vapours during degassing | Catastrophic | All non-essential personnel and ignition sources must be excluded from a minimum 15-metre exclusion zone during degassing. Use only intrinsically safe fans and equipment for forced ventilation. Continuously monitor LEL at the vent exhaust — stop work if LEL at vent exceeds 20%. Do not open manways on tank until LEL is confirmed at 0% at all sampling points. Earth and bond all metallic equipment to the tank shell to prevent static discharge. Post 'No Smoking / No Naked Flame' signs throughout the exclusion zone. | Moderate | Site Supervisor / Safety Officer |
| Exposure to residual chemical vapours causing acute poisoning | Catastrophic | Obtain SDS for all previous tank contents. Calculate worst-case vapour concentration at the work area and compare with WES (Workplace Exposure Standards). All entrants to wear SAR until 3 consecutive atmospheric readings confirm vapour levels are below 10% of WES and LEL is 0%. Standby person wears SCBA at entry point. Implement a buddy system — minimum two entrants when cleaning is in progress. | Moderate | Entry Supervisor / Entrant |
Step 2Sludge and Residue Removal
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Dermal or inhalation exposure to hydrocarbon sludge | High | Workers wear double chemical-resistant gloves, coveralls, and SAR during all sludge removal activities. Transfer sludge using vacuum pump or airlift equipment rather than manual scooping where possible. If manual removal is required, use long-handled scoops and minimise body contact with sludge. Dispose of all sludge as hazardous waste per EPA requirements. Decontamination station (water, soap, clean towels) must be set up at the tank entry prior to commencement. | Low | Entrant / Site Supervisor |
| Worker slipping on sludge-coated floor of tank | High | Deploy temporary non-slip matting or grating across the tank floor before entry. Workers wear slip-resistant chemical-resistant boots tested for the residue type. Ensure lighting inside tank provides minimum 200 lux at floor level. Limit number of workers inside tank simultaneously to prevent overcrowding. Work area must be cleaned in sections — proceed from clean areas into dirty areas, maintaining a clear escape path to exit at all times. | Low | Entrant / Entry Supervisor |
Step 3High-Pressure Water Jetting and Chemical Washing
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Injection injury from high-pressure water jet | High | Only workers holding a current High Pressure Water Jetting competency certificate may operate jetting equipment. Before commencing, verify all hose connections are rated above the operating pressure and fittings are secured with whip checks. Never direct the jet at another person. Entrants not operating the jet must maintain a minimum 2-metre distance from the active jetting area. Stop the pump before repositioning hose or adjusting nozzle. | Low | Operator / Site Supervisor |
Step 4Surface Preparation and Inspection
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Noise-induced hearing loss from grinding and abrasive blasting | High | Conduct a noise assessment before abrasive blasting or grinding commences inside the tank. If noise exposure is projected to exceed 85 dB(A) LAeq 8h, all workers in the area must wear hearing protection with sufficient NRR. Implement administrative controls: rotate workers to limit individual exposure time, sequence tasks to reduce simultaneous noisy operations inside the tank. Record noise assessments and provide results to workers. | Moderate | Safety Officer / All Workers |
Step 5Final Inspection and Tank Closeout
| Hazard / Risk | Initial Risk | Control Measures | Residual Risk | Responsibility |
|---|---|---|---|---|
| Worker inadvertently locked inside tank during closing | Catastrophic | Implement a formal entrant sign-in/sign-out register managed by standby person. Before closing any manway, standby person must call out by name and confirm visual sighting of each worker on the register outside the tank. Entry supervisor conducts a final sweep of the internal tank with a torch before instructing manway closure. Fit a 'DO NOT CLOSE — PERSON INSIDE' tag to every manway while any worker is present. Remove tags only after all workers are confirmed outside and accounted for. | Low | Standby Person / Entry Supervisor |
Relevant Codes of Practice
Worker Acknowledgement
By signing below, I confirm that I have read, understood and agree to comply with this Safe Work Method Statement.
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