Whitley Pumping Station housing site de-risking, Coventry, UK

By Simon Fullalove

Homes England, the UK government body responsible for increasing the number of new homes built in England, has used NEC to de-risk a former waterworks site in the West Midlands.

Homes England engaged contractor VHE construction in February 2020 under an NEC3 Engineering and Construction Contract (ECC) Option A (priced contract with activity schedule) to decommission a 42 m deep well and 270 m long adit at the former Whitley pumping station site in Coventry. The 9 ha former green-belt site had been acquired from Severn Trent for building 200 new homes, including restoration of the nineteenth century pumping station and lodge building.
              
The £700,000 decommissioning project started with an intrusive ground investigation to locate the 18 m deep brick-lined adit running either side of the well. A 33 m deep 0.5 m diameter borehole at the bottom of the well was then filled with bentonite grout, after which the 4.2 m diameter well was backfilled with gravel and the adit filled with grout slurry.

Despite last-minute ecological constraints and the need to resurvey existing water mains, the work was successfully completed in September 2020.

Additional works

According to Michael Chester of NEC project manager CampbellReith, ‘The local authority imposed a number of pre-commencement planning conditions shortly after the contractor had been engaged. Many of these were ecological constraints, such as the potential for disturbing bats, barn owls, badgers, breeding birds, hedgehogs, grass snakes, otters and water voles, and the presence of two designated local wildlife sites.'

In response to the planning conditions, the NEC works information was changed to include a biodiversity management plan supported by the client’s appointment of an ecological clerk of works. ‘The contractor then started early vegetation clearance in accordance the biodiversity plan and overseen by the ecological clerk of works,’ says Chester. ‘This change was managed as a compensation event under ECC clause 60.1(1) and quickly agreed by all parties, who acted throughout the project in line with the NEC requirement to work in a, “spirit of mutual trust and co-operation”. This helped to keep the main site works moving forward.’

He says that during the main site works, it became clear that a number of Severn Trent’s underground water mains were not where they were shown on the company’s assets records. ‘In response to this, the works information was further changed to include a suite of survey works to physically locate all existing water mains. This change was again managed as a compensation event.’

Despite the additional works, Chester says the contract was successfully completed in September 2020 and resulted in the timely delivery of a de-risked housing development site with clearly defined underground assets.

Benefits of using NEC

• NEC obligation to act in a, ‘spirit of mutual trust and co-operation’ meant that changes to the contract were dealt with collaboratively and quickly.
• NEC flexibility meant that changes to the works information due to last-minute biodiversity constraints and inaccurate underground asset records were readily made.
• NEC compensation event process meant the cost of additional works was quickly and fairly agreed, enabling the project to remain on programme.