Over 2,300 properties in southern England are now at a substantially reduced risk of tidal flooding following successful completion of a complex NEC-procured flood-defence project. The work involved construction of 7.2km of new and improved flood defences along the tidal banks of the River Adur in Shoreham-on-Sea, West Sussex.
Prior to the scheme, over 2,300 residential and 150 commercial properties in Shoreham and nearby east Lancing – including Brighton City Airport − were at significant risk of flooding from overtopping or failure of the existing tidal walls. The new defences will provide better protection against surge tides with a 0.33% probability of occurring in any one year (1 in 300), with crest heights based on predicted sea level rise over the next 50 years.
The Environment Agency, working in partnership with Adur District Council, West Sussex County Council and the Coastal to Capital Local Enterprise Partnership, let the construction contract for the £46 million project to framework contractor Team van Oord (incorporating local contractor Mackleys) under an NEC3 Engineering and Construction Contract Option C (target contract with activity schedule). Work started on site in September 2016 and was completed on time and within the approved budget in February 2019. The designer was Mott MacDonald and Arcadis was the ECC project manager.
The new defences are immediately downstream of the A27 road bridge and run for 1.8km along the east bank and 5.4km along the west bank. Consisting of a mixture of embankments, sheet-pile walls, rock revetments and flood glass, they are designed to last for 100 years with the option for the level to be raised after 50 years.
The project also involved improving adjacent public footpaths and creating 1.4ha of compensatory saltmarsh habitat. It won the Climate Resilience Project of the Year at the 2019 British Construction Industry Awards.
The project was procured through the Environment Agency’s NEC-based £1 billion Water and Environment Management Framework, which ran from 2013 to 2019. The framework specified that projects were to be let under either the NEC3 ECC Option A (priced contract with activity schedule), NEC3 ECC Option C or NEC3 ECC Option E (cost reimbursable contract).
According to Environment Agency project manager Tony Haffenden, the complexity and challenge of the works at Shoreham needed a collaborative approach and ‘thinking outside of the box’ to find solutions to the various challenges that were likely to arise during delivery. ‘We therefore decided upon NEC3 ECC Option C as it shares the commercial risk: it sets a target and provides a pain/gain share mechanism, so if the works can be delivered more efficiently, both parties gain a share of the cost savings. Similarly, if the value of work exceeds the target, both parties share the pain.’
He says Option C incentivised both parties to work together effectively, stimulated collaboration and encouraged a progressive working relationship between the parties. ‘It also incentivised the team to look for efficiencies and opportunities to reduce project costs, providing savings to both ourselves (and tax payers) as well as the contractor.’
Incentivising cost savings
Haffenden says a prime example of NEC incentivsation was at the W5 houseboat reach, where the contractor proposed a significant design change, shifting the flood-defence line to the landward side of a footpath. ‘As well as this change enabling the houseboat access to remain open during construction, it also presented the contractor with more working room so that the risk of obstructions that would delay construction progress was also reduced. Overall this change significantly reduced the defined costs associated with the work, providing a saving to both the contractor and ourselves.’
He says the contractual communication mechanism provided by the NEC3 ECC contract also enabled the project team to work collaboratively to identify, assess and mitigate risks as early as possible. ‘For example, prior to construction commencing at the W5 reach, an NEC early warning was raised outlining the risk of piling refusals causing high construction delay costs. This early warning prompted an NEC risk reduction meeting, where the risk was explored and a solution to mitigate against these delay costs was developed.’
A piling protocol was implemented following the meeting, where the designer specified minimum piling depths for the stability of the flood defence. If pile refusal occurred prior to the design piling depth, the contractor could check that the stability depth was met and move on to the next pile while the designer analysed the seepage risk, without delaying the construction programme.
Haffenden concludes, ‘The NEC contractual communication mechanisms were vital in facilitating these early communications throughout the project and enabling planning towards successful outcomes.’
Benefits of using NEC
- NEC ECC Option C shares commercial risk by setting a target cost and providing a pain/gain share mechanism.
- NEC incentivises both parties to work together effectively, stimulating collaboration and encouraging a progressive working relationship.
- NEC early warning and risk reduction mechanisms facilitate early communications about risk throughout a project, helping to ensure it remains on track for a successful outcome.