Client: Galliford Try
Duration: 12 weeks
Location: St Austell, Cornwall
Galliford Try needed to install two new submersible mixers at Luxulyan Sewage Treatment Works. This is a straightforward process if you can drain the ditch. But with no spare capacity onsite and a live biological process that couldn’t be interrupted, they had to find a way to carry out the installation while the ditch remained fully operational. No isolation. No divers. No second chances.
We were brought in to design and deliver a solution that would create a dry, safe working area in a live process, without compromising the flow, biology, or program. Our track record with bespoke temporary works in complex environments made us a natural fit.
Initial concepts explored wrapping the pier supporting the mixer, but we quickly saw an opportunity for a neater, freestanding solution. We developed a split Limpet Dam — a small cylindrical structure, designed to enclose the mixer location and dewater the area locally. The geometry of the dam meant loads were balanced equally, allowing us to keep the structure lightweight enough for tight crane lifts.
We produced sequencing models to walk the client through the approach, then worked with Hewson Consulting Engineers to finalise the design. The dam was fabricated in four sections by Cutlass, whose precision-made assembly and fit-up in our yard refreshingly simple.
The installation was carried out by our own team, adhering to confined space procedures. Once in place, the Limpet was sealed, dewatered, and the mixer fixed in with Galliford Try’s support. The two units were installed in a matter of days, with minimal disruption to operations and no compromise to the biological process.