Principal contractor Morgan Sindall choose Kijlstra’s precast option for Welsh Water project
Construction and infrastructure company Morgan Sindall has installed the first Kijlstra combined sewer overflow (CSO) chamber for Welsh Water on a site in Maesteg, south Wales.
The 3.5m long, 2m wide and 2.1m deep precast concrete chamber was installed as part of Morgan Sindall’s AMP6 framework contract with Welsh Water.
The works involved installation of the new precast CSO chamber plus mechanical screen and associate pipelines and manholes. The 17-tonne CSO chamber was manufactured off-site and installed using a 60-tonne capacity mobile crane.
This was followed by the two-tonne internal weir wall, grouted in place once the chamber had been positioned within its excavation. The CSO riser unit, weighing another seven tonnes, was then lifted into place on top of the base unit.
Preparation works in advance of the chamber’s delivery included construction of a 5m x 4m x 3m cofferdam and a concrete blinding slab.
Morgan Sindall’s site agent Mark Thomas said the precast option was chosen after careful consideration of all the alternatives.
“We basically had three options – in-situ concrete, a plastic chamber or precast. Precast was the way forward for a number of reasons,” he says.
Morgan Sindall chose the precast option to eliminate and minimise risks associated with a traditional in-situ pour – including working at height, steel fixing, manual handling and concrete works.
As well as the health and safety benefits, the precast option also saved time on the overall programme, effectively reducing the 12 days required for in-situ concrete to just one day to install Kijlstra’s factory-finished product.
Mark has used Kijlstra precast units, including MCC bases and drawpits, on other Welsh Water projects but this is the first time he’s installed one of the company’s CSO chambers.
“We usually choose precast but it all depends on space. More often than not a crane is needed to lift the unit and that’s not always possible. That’s when we’d go the in-situ route.”
Installation of precast units drastically reduces on-site activity says Mark but he cautions that preparation is key.
“You’ve got to prepare everything meticulously and be ready as soon as the unit arrives on site,” he says.