The innovation of modular steelwork is making the construction of a major wastewater treatment plant in Liverpool safer, faster and more cost effective.

GCA (Galliford Try, Costain & Atkins) JV is building the UK's first multi-storey CASS (Cyclic Activated Sludge System) sequencing batch reactor (SBR) plant in partnership with United Utilities.

"To innovate the steelwork installation, we had to challenge the traditional methods – how could we make it safer and faster but at the same time improve quality?" said Alistair Smithyman, Design Coordinator on the project.

The team decided on modular construction, where an area or section of the works arrives to site in a pre-assembled state, ready for lifting into position.


This has the benefit of greatly reducing site installation time and increases site safety by reducing exposure to working at height. The quality of the product is superior as it is assembled in factory conditions; any modifications can be undertaken before it comes to site, with no site welding required.

Costs are competitive; although generally modularisation requires additional steel to make the scheme work, this is offset by reduced transportation costs, labour and crane requirements for the erection.

This innovation was kick-started by the design and installation (with Supply Chain Partner Peers Ltd) of the high-level decanter cover steelwork platform. The platform was an expanse of 2800m2, sitting at the top of the SBR (18m above ground floor level), with 7m open drops to the basins below.

The issue of working at height and restrictive access conditions meant that alternative and innovative installation methods needed to be used. The platform was split into eight areas, (approximately 350m2 each). Each area was then split into 14 separate modules. Each module was delivered to site and installed in a completed state, inclusive of all handrailing and edge protection to ensure working at height needs were minimised. Each area took a total of two days to install and complete.

(CD)