Public swimming pools are highly valued assets for rural people who live a long and dusty drive from the beach.
So when the residents of Monto, 200km west of Bundaberg, learnt that their 25-metre pool had a structural problem, they were duly dismayed.
North Burnett Regional Council, who own and manage the asset, found the pool had sunk into the ground by about 200mm towards the deep end. Consequently, water in the reticulation gutters would no longer drain to the shallow end, meaning the reticulation system wouldn’t work and therefore the water couldn’t be filtered properly.
The council had three options:
- Re-do the plumbing and replace the filter system (at a cost of about $50,000), but even if they did that, the pool’s level would still be out of kilter, and at risk of further sagging.
- Build a new aquatic centre (at prohibitive cost) for the little town of Monto (population 1500).
- Find a less costly method of re-levelling the pool in a structurally sound manner.
So they explored the third option and ultimately gave the job to Uretek, which is in the business of injecting expanding resins through a series of small holes in order to raise and re-level anything from pavements to warehouse floors or airport runways.
The task called for careful planning though, because the pool had been built using a number of pre-cast concrete sections. The walls were pre-cast with flat bases, and infill concrete pre-cast sections formed the floor. In addition, the floor joints were set down with mastic filler and the vertical joints were mastic filled.
These pre-cast sections posed a problem, because if Uretek over-lifted any one section it might result in breaking the joint. Or else, due to its large pre-cast base, the wall could easily rotate inwards or outwards.
Moreover, as the floor slab was sitting on a step joint, the internal slab could not be lifted because it might lift at the joint and not lend itself to being lowered once that joint had been filled.
All these factors demanded a slow process of lifting each pre-cast wall section a little bit at a time, and slowly bringing the pool back to an acceptable level. Once this was done, the correction of levels was proved by pouring water into the gutter to ensure it flowed to the shallow end again.
Only then did Uretek very carefully fill the voids under the internal pool slab.
“They had the pool back in business after just ten days, and we were delighted,” said North Burnett Regional Council Project Manager, Trevor Harvey.
According to Uretek Supervisor Ryan Eddington, the key to the project’s success was being able to pick precise injection locations and depths to ensure none of the joints were damaged.