CEEQUAL rating of Very Good for pumping station replacement project

Following Defra funding approval for the estimated £38 million cost, work commenced on the construction of the new state-of-the-art pumping station. The goal was to future-proof the station, whilst ensuring as much of the surrounded area was conserved.

Atkins Ltd had been working with the Middle Level Commissioners on the St Germans scheme since 2003. The work was done in three phases. The first, a feasibility study, involved an extensive option study and environmental impact assessment, culminating in the successful Defra application. The second phase consisted of detailed design, pre-qualification, planning and phased tendering (three distinct contracts). This took 18 months, with the third phase of site implementation works, expected to take approximately three years.

The site implementation was broken down into civil enabling works, construction of the new pumping station and the demolition of the existing station. The first part of the civil enabling works, by the contractor Costain Ltd, was the installation of a 1.7-km-long, stone-surfaced access road, running from High Road at Tilney-cum-Islington down to the main works area. This was completed in January 2007 and will ensure that site traffic is routed away from the local community.

The second part required the installation of a twin-walled, steel-sheet-piled cofferdam out into the tidal section of the middle level drain. In addition to the cofferdam, the existing drainage channel was diverted around the works on the eastern bank of the channel to enable the continuing operation of the existing station.

Installation of the cofferdam enabled phase two of the site works – construction of the new station – to be erected in a dry environment. Continuous flight augured piles provided the platform from which to build the superstructure. This structure now houses six concrete volute pumps, capable of pumping 100 cubic metres of water per second.

In the later stages, the pumps, mechanical and electrical equipment were installed by contractors KSB and Birse Water. With connection to a new electricity substation constructed for the station, each pump has variable speed and has a dedicated 11-metre-long motor control centre. They also each have a transformer and 1700-kVA stand-by generator.

The Environmental Impact Assessment (EIA) survey involved a number of rounds of consultation with statutory and other interested parties. The output of the EIA formed a significant element in the derivation of the preferred option. Key features of the EIA were the traffic management plan, assessment and mitigation of any visual amenity disturbance, the introduction of mitigative ecological habitat and the assessment of construction noise on the surrounding environment.