Water treatment works upgrade, Lancashire, UK

NEC has been used to upgrade a major water treatment works in northwest England. Client United Utilities let the £18 million design and build project to contractor Mott MacDonald Bentley in January 2020 under an NEC3 Engineering and Construction Contract (ECC) Option A (priced contract with activity schedule).

The work involved replacing 147 life-expired pressure filters with eight rapid gravity filters, providing a new dirty backwash storage and treatment system, increasing the capacity of the adjacent raw water reservoir and raising the works treatment capacity to 105 Ml/day.

The new rapid gravity filter structure was built on 83 precast concrete piles and 49 circular steel tube piles bearing on shallow bedrock. Backwash water from the filters is now collected in two new 500 m³ tanks and then treated in a set of four new lamella (inclined plate settler) clarifiers. The reservoir capacity was increased 3% to 12.4 million m³ by raising the overflow weir and concrete core by 300 mm and 535 mm respectively.

Despite numerous challenges, including Covid-19, extreme weather, scope changes and the unknown condition of 90+ year old assets, the work was successfully completed to the agreed revised budget and programme in January 2023. The project was shortlisted for the Upgrade and Renewal Project of the Year in the 2024 British Construction Industry Awards.

Collaboration key to success

Mike Tillery, delivery manager at United Utilities, says the NEC requirement to act in a ‘spirit of mutual trust and co-operation’ was embedded into everything the project team did. ‘NEC-inspired collaboration was absolutely key to the success of this project. It was required throughout the delivery of the works from a planning and programming perspective.’ 

He says the fact that construction took place on a live water supply and treatment scheme was a particular challenge. ‘It meant that the priorities of our operational teams had to be embedded into the contractor’s plans and programme. We also had to minimise disruption to the people who used the reservoir for wallking, fishing and boating.’ 

Mr Tillery says ECC Option A was chosen as the upgrade was considered to be relatively straightforward project with an experienced contractor prepared to manage the financial risk. ‘However there were some risks identified at tender stage concerning operational functionality of the works. We agreed to take these on as employer’s risks, and some of these did occur.’

Managing risks

He says the NEC requirement to regularly submit and agree revised programmes throughout the contract also contributed to the project’s success. ‘Programming was a collaborative effort that involved both our capital delivery and operational teams along with the contractor. Monthly meetings were held to ensure there were no clashes between construction activities and critical operational activities.’

Where construction activities were delayed or postponed due to operational priorities, Mr Tillery says the NEC early warning system helped to mitigate the impact by enabling the contractor to deploy resources elshwere. ‘Compensation events were notified where delays were unavoidable, the time and cost of which were promptly agreed by both parties in a collaborative manner.’

Mr Tillery says the contract was managed using the Thinkproject (formerly Cemar) contract management system. ‘This proved to be a very useful platform. Early warnings were raised and logged on the system, which gave the whole project team visibility of the risk and subsequent actions to manage it accordingly and minimise the impact and cost.’

Benefits of using NEC

• NEC-requirement to act in a ‘sprit of mutual trust and co-operation’ ensured the necessary collaboration with the operators and users of the existing water supply scheme.
• NEC flexibility enabled use of a priced contract option with additional employer’s risks set out in the contract data.
• NEC requirement to regularly submit and agree revised programmes throughout the contract helped avoid clashes with construction and operational activities.
• NEC early warning mechanism helped to identify and mitigate risks, and NEC compensation events were promptly agreed by both parties in a collaborative manner.