The category-winner Swansea Wastewater Treatment Works is the uk's first completely enclosed wastewater-treatment plant, and is the central component of a major scheme to improve the water quality in Swansea Bay.
To meet planning requirements, the structure is buried and landscaped over with an attractive southern elevation. Economics demanded a small footprint, which required a compact, complex arrangement of tanks and plant rooms. Concrete was the preferred option for the construction of the complex structural forms for durability, low maintenance and strength:weight ratio.
The size of the structure, 200m-long by 53m-wide and 15m-deep, gave the contractor, Laing Civil Engineering, the opportunity to use very large pours for many of the larger in-situ sections of the structure. Beneath the lamellar plates of the secondary settlement tanks there is a system of hoppers for the collection of sludge. These make up an 'egg box' and were particularly complex to form, especially in view of the pipework that had to be cast in to link with the galleries below.
The structure combines in-situ and precast concrete components into a cost-effective construction solution that is visually pleasing. The superstructure and roof over the aeration lanes and secondary settlers consist of precast roof units supported by precast beams on in-situ columns. The design is similar in concept to a four-span highway viaduct deck. It gave an optimum solution with minimal long-term maintenance and enabled the tight construction programme to be achieved.
As well as the main works, there are two large sludge digestion tanks constructed in concrete with precast concrete roofs. These are both 21m diameter and 18m deep.
OWNER Hyder Utilities
ARCHITECT Percy Thomas Partnership
CONSULTING ENGINEER Hyder Consulting
DESIGN PROCESS OTVB
MAIN CONTRACTOR Laing Civil Engineering
READY-MIXED CONCRETE Ready Mixed Concrete (Wales)
CEMENT Blue Circle Cement
FORMWORK Donal Hayes and Sons Building and Civil Engineering
PRECAST CONCRETE Birchwood Concrete Products