Mill Fleam flood pumping station, Derby, UK

Mill Fleam flood pumping station, Derby, UK

Derby City Council has used NEC to deliver an award-winning scheme to protect around 250 city-centre commercial properties from the increasing risk of flooding. The Mill Fleam pumping station on a tributary of the river Derwent won the Environment Project of the Year in the 2023 British Construction Industry Awards.

The council let the £7.5 million design and build project to JBA Bentley in November 2021 under an NEC4 Engineering and Construction Contract (ECC) Option A (priced contract with activity schedule). The scheme became operational in December 2022 and the contract was completed on time and budget in August 2023. Arcadis was the NEC project manager.

Located in Bass’ Recreation Ground near the city centre, the works involved providing dual gates to stop Derwent flood water entering a culverted part of Markeaton Brook, and a new bypass pumping station to maintain flow in the brook when the gates are closed. The scheme is part of the council’s Munio (meaning ‘to fortify’ in Latin) series of flood management projects that were part-funded by the European Regional Development Fund. 

The multiple fish-friendly submersible cannister pumps have a total capacity of 4500 l/s and feature variable frequency drives and intelligent operation for maximum efficiency. The contract included building reinforced-concrete flood control and pumping structures, steel-sheet-pile flood defence walls, a standby generator, plant building, landscaping  and environmental works – such as 75 new trees and a downstream fish refuge.    

Ideal contract

millfleam3.jpgThe council’s principal project engineer Murray Parker says NEC4 ECC was chosen as it is a proven form of contract. ‘NEC is ideal for procuring civil engineering schemes such as Mill Fleam pumping station. In particular, the requirement in the contract to act in a “spirit of mutual trust and co-operation” provided a great incentive for collaboration between all parties involved in delivery.’ 

He says project funding was fixed, giving the council limited provision to accommodate change. ‘The concept design by Arcadis was therefore developed through early contractor involvement prior to contract award and NEC4 ECC Option A was selected as the preferred contractual mechanism. This lump sum contract gave us much greater certainty on the final cost outcome by transferring risk to the contractor.’

Murray says that NEC-inspired collaboration during the early contractor involvement stage led to 70 t of embodied carbon dioxide being cut from the outline design. ‘This was primarily achieved by incorporating wet-well temporary works into the permanent structure, rephasing channel works to use the new pumping station for dewatering, and redesigning the concrete mixes.’ 

Additional emissions savings resulted from three-dimensional printing of concrete pile caps, cladding panels and access stairs offsite, by using vegetable oil instead of diesel in site plant, and by installing high-efficiency pumps with variable-speed drives.

Adding value

NEC project manager Philip Jordan of Arcadis says NEC added significant value to project delivery. ‘Through regular NEC early warnings between the parties, risks were identified early with mitigation measures discussed and implemented before they became issues.’

He says where changes occurred, in each instance an early warning had been raised and discussed beforehand. ‘This resulted in building a “no surprise” culture. The project was delivered during a time of spiraling inflation and reduced supplier availability, so the NEC early warning facility was vital  to achieving the project cost and programme targets.’

Jordan adds that a valuable lesson learned from the project was to open early warning meetings with a tour of the site. ‘This allowed attendees to visualise and contextualise the issues for discussion. Through watching progress unfold on site, the parties could discuss successes as opposed to focusing on the negatives of a given situation.’
 

Benefits of using NEC

  • NEC requirement to act in a ‘spirit of mutual trust and co-operation’ encouraged collaboration between all parties, leading to significant environmental benefits.
  • ECC Option A provided the client with greater certainty on final cost by transferring risk to the contractor.
  • NEC early warnings and meetings ensured all risks were identified early, with mitigation measures discussed positively and implemented before they became issues.
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