In the latest edition of Safety Digest, UK MAIB analyzes the hazards behind grey water exposure and its impact on one’s health, discussing a grey water incident that took part onboard a ro-ro ferry where the crewmembers undertaking the task were taken to the hospital vomiting.
The Incident
The crewmembers on a ro-ro ferry were ordered to replace a part of pipework on the vessel’s aft waste water system. The pipework that needed to be replaced contained grey water, untreated from the outlets of showers and sinks.
Two senior engine room ratings and an assistant motorman were assigned to conduct this work; Following a briefing in the engine control room they went to the aft waste water plant.
Firstly they set valve isolations intended to divert grey water away from the affected pipework. At that moment, one of the senior ratings was called back to the ECR for the entering harbour ‘standby’ requirement.
When the two remaining crew released flange bolts to remove the pipework, grey water started to pour out. Although they tried to reseal the flange by replacing the bolts, this was unsuccessful and both were then soaked in grey water.
Looking for help, one of the soaked crew slipped and injured his back when they were heading back to the ECR. While a first-aid party attended to the casualty, the second engineer proceeded to the aft waste water plant, where he quickly realised what was wrong and isolated the flow of grey water.
Following, the crew who had become soaked felt ill and started vomiting and were sent to hospital, from where they were released the same day.
The investigation that followed revealed that the crossover valve between the forward and aft waste water systems had been left open, allowing grey water from the forward system to enter the section of pipework being removed from the aft system.
Τhe investigation also identified that the ‘tag out’ procedure for isolating live systems had not been used and there was no risk assessment for the task.
Lessons Learned
- Exposure to grey water is potentially very hazardous and could result in serious illness. Therefore, maintenance on waste water or sewage treatment systems must be fully risk assessed to identify and protect against all the hazards. In this case, the exposure led to vomiting, and it was fortunate that the affected crew could be taken to hospital quickly and receive treatment.
- When undertaking work of this nature, the plan for isolating that part of the system requiring maintenance should be subject to a detailed plan and appropriate ‘tag out’ isolations. This will ensure that onboard services are maintained while system isolations are effective. The second engineer realised what had happened when he arrived in the plant room; this indicates that the plan for isolations was either incomplete or had not been undertaken correctly.
- The opportunity for in-service maintenance on ro-ro ferries will often be limited due to busy schedules and short turnarounds. Nevertheless, planned work should take these constraints into account, ensuring that the correct level of manpower and oversight is in place. It was unhelpful in this case that one of the team of engineers was called away.
- PPE is an important layer of defence to protect crew. If there is any risk of exposure to hazardous material, consideration should be given to wearing suitable PPE just in case things go wrong.
Recently, Carnival Corporation was accused of dumping grey water into Alaska’s Glacier Bay National Park, prepared ships in advance of court-ordered audits to avoid unfavourable findings, falsified records and dumped plastic garbage into the ocean.
