Lustrum Beck flood alleviation scheme phase 1 (Newtown and Bishopton Road), UK

Lustrum Beck flows through the centre of Stockton on Tees in north east England. A major £12 million flood alleviation scheme was proposed in 2003 although affordability issues led to the scheme being paused. In 2012 flooding affected 150 homes, infrastructure and businesses in 2012. A innovative alternative costing just £3.5 million has since been developed and was completed in April 2017, with key parts being procured using NEC.
 
The scheme’s seven main elements were individually delivered by Stockton Borough Council and the Environment Agency. Two of the Environment Agency’s projects involved replacing ageing flood walls and an embankment in the Newtown area with set-back defences. Both projects were designed and built under the NEC3 Engineering and Construction Short Contract (ECSC).
 
The new £550,000 Newtown flood bank on the south side of the river was delivered Breheny Civil Engineering between May and September 2016, with additional channel naturalisation carried out between February and April 2017. The existing 1.5 km clay embankment was rebuilt on a new alignment away from the river to allow more room for flood water. The new alignment is also 800m shorter, reducing the risk of erosion, and higher to improve flood protection.
 
On the opposite bank a new £200,000 sheet-piled flood wall next to Bishopton Road was delivered by Esh Construction between September 2014 and January 2015. It was accelerated in the programme and completed as urgent works due to two vehicle collisions with the old flood wall. Combined with other elements of the scheme – including the council’s replacement of Londonderry Bridge on Durham Road under an NEC3 Engineering and Construction Contract (ECC) with Balfour Beatty – the new defences provide a greater than 1-in-75 year level of flood protection.

Focus on collaboration

According to Ted Thomas, project team manager with the Environment Agency’s National Capital Programme Management Service, ‘We use NEC3 contracts as standard for our main construction frameworks and call-off contracts due to their simplicity, plain language and focus on collaboration.
 
‘In this instance, we chose the ECSC due to its simpler administration than the ECC and because of the relatively modest scale and complexity of the works. The reduction in named roles compared to the ECC also allowed us to work more effectively and efficiently given the low level of project risks. In the event the ECSC proved very successful on both contracts, providing us with effective management of costs and change.’
 
On the Bishopton Road flood wall, Thomas says the urgency of the works meant there were inevitably a number of changes on site. ‘One example was the discovery of services closer than expected to the existing wall. This led to a change from a cantilever gravity wall to a sheet-piled wall. The NEC process of agreeing and negotiating compensation events made it simple for both parties to agree to share this risk given the speed with which the site was mobilised.’

Contract flexibility

On the subsequent Newtown flood bank contract, additional funding for naturalisation of the river channel was made available after the embankment works had been completed.
 
‘It proved more efficient to use the existing contractor and its suppliers to undertake the design and construction of the naturalisation work,’ says Thomas. ‘The flexibility in ECSC allowed the additional environmental work to be carried out as part of the existing contract, even though it was started five months later.’
 
Work on the second phase of the flood alleviation scheme, due to start in 2017, involves creating extra flood storage in the catchment upstream of Stockton and forming a new wetland habitat.

Benefits of using NEC

• NEC’s use of plain language ensures a clear apportionment of risks and with a focus on collaboration.
• ECSC provides an administratively simple NEC works contract, which is ideally suited for smaller, low-risk projects.
• NEC processes of early warnings and compensation events make it simple for both parties to negotiate or share risks as they arise.
• NEC flexibility allows additional work to be added to the scope after completion.