A tight squeeze

Image: The team entering a bridge beam. The height here is only 600mm.

Working in tight spaces can provide a whole array of challenges for infrastructure teams. The team at Mines Rescue are there not only to extract workers from difficult sites but also to provide the knowledge and expertise to prepare for such eventualities.
By Mary Searle Bell

North of Kaikoura, the Clarence River Bridge carries SH1 high across the water. It’s a picturesque spot, with the smooth lines of the box girder structure highlighting the rugged scenery beneath it.

Late last year, as part of its routine bridge maintenance, engineering firm WSP undertook an internal inspection of the box girder, a job that posed challenges due to the lack of space inside. To facilitate the job and help if something went awry, WSP engaged Mines Rescue to create and execute a risk assessment and rescue plan. 

Built in 1969, the bridge itself is just over 300 metres long and comprises six spans – four main spans at 61 metres each and two 30.5 metre end spans. The depth of the superstructure varies from 3.2 metres at the pier supports to 1.1 metres at mid-span.

“There were a few difficulties with this job,” says Mines Rescue Chief Executive Trevor Watts.

“First, the size of the access point was just 530mm square, and the space inside the span was only 510mm wide and 600mm high – we didn’t bring any of our big boys on this job!”

Trevor says that WSP engaged Mines Rescue on a similar job back in 2023, so a working relationship had already been established between the two organisations.

“WSP applied a high level of due diligence to this job. They’re great people to work with in this respect – we’re singing from the same song sheet when it comes to the health and safety of our people.”

He says that the inspection work in the confined space is relatively easily managed, but those tight spaces have to be factored into a rescue plan. Most importantly, how could you get someone who’s incapacitated out?

“We started by doing a risk assessment. WSP gave us the as-built drawings of the structure so we’d have a mental picture before we sat down to do the risk assessment. We soon discovered real challenges were getting in and out of the structure, as well as moving through it – the spaces were very small.

“We then ran two workshops. The first was a planning one. We simulated the bridge pier out of wood that replicated the internal pier wall. We also duplicated the small hatches and the tight diaphragm through the pier we’d have to climb through.

“We then used this to determine the methodology for entry and exit, and once that was sorted, we started working on a rescue plan,” says Trevor.

At the second workshop, the two engineers from WSP who would be doing the bridge inspection joined with the seven Mines Rescue personnel who’d be working alongside them to practice entry and exit through the access hatches and diaphragm. The engineers were already trained in working in confined spaces.

The nine men then practiced a rescue scenario as part of a rehearsal of the rescue plan. In the tight confines of the model, they strapped someone to a stretcher and manoeuvred them through the pier diaphragm and successfully out of the access hatch. Proving, that although difficult, the job could be done.

“One Mines Rescue team member was our safety person. It was his job to monitor the entry and exits into the bridge – counting heads in and out. He was also in charge of comms. 

“Three team members went inside the structure with the engineers – two going ahead to prep the entry through to the next pier diaphragm,” says Trevor. 

“Their job was to put in anchors for the rope system. The third stayed with the engineers – he had a gas monitor (not that we were expecting anything as the bridge was well ventilated) and a major trauma backpack. The team inside were also in charge of providing lighting inside the structure.

“Then we had a further three team members outside. They would be part of the rescue unit if it was needed and had stretchers ready to go. The team inside could summon them by calling the safety person on the radio system.” 

The chances that a rescue would be needed during the bridge inspection work were low, but not zero. The climb up inside the girder through the hatch was 1.8 metres from the floor and posed a fall risk, and Trevor says there’s always the chance of a medical event – a heart attack for example – incapacitating someone while working inside the structure.

Once on site, as the health and safety lead, Mines Rescue started the project with a pre-start meeting and the work got underway. The job took two days to complete.

“We’d take a break every two-and-a-half to three hours, and used that to rotate the Mines Rescue team out,” says Trevor.

“The job went according to plan and clearly showed the benefits of having a robust risk assessment, planning workshops, and a rehearsal.

“I take my hat off to WSP, they did a lot of due diligence and had the support of the Transport Agency. It’s all well and good to have a plan, but to actually practice it is next level.”

Mines Rescue, as the name suggests, specialises in rescue work in mines and tunnels. Because of this, they are ideally suited to any confined space work, as they have the skills and experience to undertake the job from risk assessment to managing the work and supplying personnel, equipment, and resources. 

“Our guys have a broad range of skills, including rope rescue and gas detection. They’re all trained in advanced first aid, they can deal with severe bleeds, provide oxygen therapy, and are competent in CPR, stretcher extrication techniques, patient care – and all done in tight and difficult spaces,” says Trevor.