Key learnings from a High Potential Incident.
HPI OSH Alert #484
Date of incident: 29 July 2016
Safety Flash issued: 10/08/2016
On 30 July, complaints were
received from members of
the public regarding
wastewater odour issues.
Operations crews were
dispatched and identified
that an access chamber on
the Main Sewer line had
been cored, with a pipeline
inserted to enable a connection to a new odour
The connection point was not adequately sealed,
causing odours to the surrounding area.
While coring into the side of the access chamber,
appropriate controls were not put in place to ensure
adequate protection from potential hazardous gases
(i.e. Hydrogen Sulfide - H2S) from the main sewer.
Why did this happen?
- Project management procedures were not followed to ensure appropriate controls and supervision of
high risk activities.
What will the business area involved in the incident do to stop this from happening
- Re-assess competency of all relevant operational Clearance to Work (CTW) authorised persons.
- Develop and implement a management reporting system for project hold points (i.e. project risk
assessment, construction risk assessment etc.) enabling management oversight.
- Review Principal contractor and subcontractors capability to deliver remaining works in progress
- Review the contractor engagement process to identify opportunities for improvement around
prequalification, bid assessment and Verification of Competency for high risk works.
What will our organisation do to stop this from happening again?
- Develop a network-wide gas monitoring program for main sewers to better understand the risks
associated with hazardous gas levels in a closed sewer system.
- Conduct a risk review to determine how to proceed with existing asset security. Develop a 1–3 year
plan to build in-house capability for odour management.
- Review current process and controls for opening main sewer and pressure main discharge access
- Identify opportunities to improve current CTW process, including additional entry permit to cover
opening main sewer and assignment of specific competency.
What key learnings can you discuss with your team to stop this from happening
High Risk Work construction activities must have adequate levels of risk mitigation
measures in place
- How do we ensure adequate levels of supervision and competency for any High Risk Work activities?
- What is the current process for our teams to ensure safe job planning documents are reviewed and
feedback is given?
- Have we developed and implemented a formal process to ensure safe job pre-planning and a
coordinated approach to the planned work occurs?
When multiple parties are involved in planned work, it is crucial to have a clear
understanding of all roles, responsibilities and activities across the entire job.
- When would a Clearance to Work be required?
- What is the role of the Contract Manager and Authorised Person in the Clearance to Work process?
- If a job changes, what do we need to do or who do we need to contact, to make sure we continue
- How does our team discuss our planned work and the potential risks of the activity?
Main sewers and pressure main discharge access chambers may have elevated levels of
hazardous gases (and operate under pressure) that can pose hazards to the surrounding
- Be aware that we can have very high concentrations of H2S in our wells and pipes. Water
Corporation have measured concentrations higher than 1200ppm within our sewer systems.
- The health effects of hydrogen sulphide (H2S) depend on how much H2S a worker breathes and for
how long. However, many effects are seen even at low concentrations. Effects range from mild,
headaches or eye irritation, to very serious, unconsciousness and death.
- What are some of the controls required to be in place before accessing a main sewer access chamber?
If you would like further information about anything included in this HPI OSH Alert, please contact Charis
Neumann, Senior OSH Analyst Incidents, (08) 6330 6629.