A dynamic partnership approach and a delivery strategy that places sustainability best practice at its heart, is helping to bring considerable social and environmental value to a flagship mixed use development in Hampshire.
A 208.4ha greenfield site is gradually turning into what its developer, Grainger, envisions will be a “village conservation area of the future”. The site at Berewood, near Waterlooville, will eventually contain 2,550 new homes, retail areas, a primary school and various community facilities. This has been designed to have as little impact on the natural environment as possible, and features a comprehensive development-wide sustainable drainage system (SuDS).
Principal contractor, PJ Careys, played an active role in establishing an effective partnership with client Grainger and design engineers Mayer Brown, with each having a collective commitment to sustainability. Key to this for PJ Careys was enabling its teams to drive the pursuit of sustainable construction on-site.
Development plots are being released in phases, with key roads, drainage and SuDS infrastructure installed prior to the housebuilders arriving. Since 2013, PJ Careys has been working on-site to deliver the enabling and infrastructure works on behalf of Grainger. To date, PJ Careys has delivered works over a number of phases. These include the construction of a spine road through the site, a river diversion and hard and soft landscaping. PJ Careys also installed a vast number of SuDS infrastructure and associated drainage, and carried out Section 278 works to the local highway.
The showpiece element of the development is the SuDS provision. Flooding is a particular risk on the site, as the soil is predominantly a sandy clay material with poor capacity for infiltration. The SuDS is intended to minimise flood risk, as well as improve water quality throughout the site and encourage biodiversity.
The SuDS, designed by Mayer Brown, consists of interlinked drainage and landscaping with a mix of vegetated channels, retention basins, wetlands and swales combined with underground storage tanks and complex control devices. PJ Careys has experience of installing SuDS infrastructure, but the scale of the system at Berewood, and its role in the visual appeal of the development is new.
“At Berewood we had the right team in place, who were proactive and happy to think differently to find aspects of our work that could be enhanced and value engineered,” says PJ Careys’ contracts manager Mick Futcher.
“From this, our delivery programme evolved to meet the client’s objectives. We had a good working relationship with the project partners and subsequently a number of great contributions resulted from our site team. This included community benefits and project-wide carbon savings.
“The SuDS here is extensive and will ultimately prove the success of the development in years to come through flood management, as it is joined up with lots of other aspects of the development.
“There is a large amount of work just on the aesthetic side of it: the swales were all planted with wildflower seeds, and the headwalls are built in flint.”
At the south west of the site, the SuDS discharges to an existing ditch system, and at the north it discharges into the River Wallington, which crosses the site, separating the main residential areas from the retail zone.
A new 16m span FlexiArch bridge – currently the world’s longest “flat pack” arch bridge, built by supplier Macrete – has been constructed over the river to link the northern and southern parts of the site, and provide access to a new primary school (see box).
PJ Careys’ proactive approach to working with its project partners instigated some significant value engineering benefits, including the decision to reuse as-dug material as backfill in some of the drainage trenches, rather than foamed concrete – a decision that saved 3,200m3 of foamed concrete and avoided 400 related vehicle movements of concrete trucks.
Elsewhere on the site, where the ground was sandy clay, PJ Careys opted for a fill material containing recycled incinerator bottom ash.
The same product is being used as the sub base for footpaths throughout the development. Another value engineering success has been replacing the concrete fill above the FlexiArch bridge with lime-stabilised as-dug material.
“The advantage of this option was that it eliminated the requirement to import virgin material, and subsequently we only used site-won material, this had a consequent environmental benefit,” says Futcher.
The same method was used to stabilise existing material for the capping layer under the new roads.
Community engagement has been an important feature of the project. Houses have been constructed with owners moving in alongside the civils work, and there is a new primary school in the middle of the site.
The community engagement extends to the fact that 75% of labour on site is local and 47% of the work by value has been placed with local suppliers and subcontractors.
PJ Careys group sustainability and environment manager Clare Masters says that the project has helped to shape the company’s sustainability strategy.
“This project started before PJ Careys’ sustainability journey really began, and it has definitely helped us to better focus strategies and actions that balance the trade-off between social, environmental and economic considerations.
“We know that we can take a lot of these measures forward – the local labour, the community engagement, the environmental aspects, value engineering and lean construction – and apply them to other construction projects. In the process this is helping to develop best practice and create long-term value for our clients.
“The sustainable actions may seem like small things individually, but when you add them up, they really do contribute.”
The new 16m span bridge has been designed as an architectural feature and gateway to the Berewood site.
It was formed using Macrete’s FlexiArch modular, precast, concrete arch bridge system that uses the same principles as traditional stone masonry-built arch bridges.
berewood innovative flexi arch bridge
Individual concrete tapered blocks – precast with the correct taper for the span – are connected by a polymeric flexible membrane, which allows the arch to be delivered flat and then formed into its perfect arch shape as it is craned into position.
At Berewood, PJ Careys prepared the site by installing piles and forming concrete footings joined by tie beams below ground.
When the arch sections arrived on site, they were lifted into position, fitting directly into the concrete footing beam.
Spandrel sections were lifted in at each end of the arch and grouted into place before the whole structure was backfilled.
The bridge brings added benefits over traditional stone masonry built bridges due to the time and associated cost savings of between 15% and 20%.
The site team also created the architectural statement that Grainger was looking for, PJ Careys faced the entire structure in a combination of red brick and local Hampshire flint.
In association with PJ Carey (Contractors)