The challenge of delivering up to 725 new homes at Conningbrook in Ashford, Kent, while ensuring no overall increase in nutrient levels in the Stodmarsh Special Area of Conservation, is one Redrow and its development partner Quinn Estates have met with a pioneering solution.
new homes
wetland created at a cost of £3.5m
of open space including play areas, a village green and a park
including a primary school, community building, bowls club & local centre
By cleverly engineering a new £3.5 million wetland on a neighbouring site, to naturally filter out excess nitrates and phosphates from the Great Stour River, they have been able to ensure nutrient neutrality, while providing new habitats for wildlife.
Quinn Estates secured the allocation of the land, and a subsequent hybrid planning permission for the wider Conningbrook site and the first phase in January 2022. The off-site wetlands were given the
green light by Ashford Borough Council in July 2022, with subsequent approval from the Environment Agency in November 2022.
Redrow will be building the first phase at Conningbrook, which features 288 much-needed new homes, and a local centre to be delivered by Quinn Estates, while leading on the creation the wetlands, new primary school, parkland and a village green, alongside a new community building and home for Ashford Town Bowls Club.
A further 437 homes at the location will be subject to reserved matters planning.
The wetlands method works by extracting a small portion of the flow from the river, sending it through specially planted reed beds, which help to filter the nitrates and phosphates from the water, before the water rejoins the main river.
Located to the east of the Conningbrook development, the new wetlands have been created on former agricultural land, which had acted as a functional floodplain.
While the wetlands site has been created to appear as natural as possible, with the planting of 140,000 reeds its natural core, it’s underpinned by engineered infrastructure.
Its main components are two precast concrete river headwalls, submerged throughout the year on the bank of the Great Stour River. The first of these headwalls extracts water from the river, and a ‘wet well’ station, connected to the headwall via a buried pipe, brings water into the reed beds. Water is pumped from the wet well to the wetlands by an electric pumping station.
The inflow rate is controlled across the year, varying from 400m3 per day during summer months and up to a maximum of 2,000m3 per day between mid-December and mid-April.
The reed beds, planted in open water, have been arranged in a series of cells, each surrounded by raised earth ‘berms’. Water is brought in via two equal flow paths, which each travel through three reed cells.
A portion of excess nutrients are removed from the water through a combination of sedimentation, plant growth and denitrification processes. The water then leaves the wetlands and returns to the river via the second riverbank headwall. Native species-rich grassland, shrubs and trees have been planted to provide habitats for wildlife and screening around the pumping station and other engineered features.
The wetlands became operational in January 2024, just prior to the first home completions, as was a requirement of the planning permission. As the wetlands are located next to Conningbrook, alongside the Great Stour River, Redrow and Quinn Estates have reached an agreement with the landowner to lease the wetlands site for 100 years.
During the nine-months of construction, the wetlands site has been carefully managed and monitored by their designers Water Design Engineers, including mitigating any impact on local wildlife and the river itself. Following an ecological appraisal by Aspect Ecology, measures were taken to protect and enhance the riverbank and hedgerows nearby during the works, including the removal of invasive species such as Himalayan Balsam.
Future care of the wetlands will be undertaken on behalf of Redrow, Quinn Estates, and the local community, by Trustgreen, an open-space management company which specialises in promoting natural habitats and biodiversity.
As well as cleaning water from the Great Stour, the wetland will deliver an additional area of habitat for native wildlife; it is likely to be attractive to a range of insects, birds and amphibians. The wetland area will be partly accessible via an existing public right of way, a concrete path and bridleway, which has been enhanced as part of the works, with the area cleared of overgrown vegetation for access. The wider development site will also eventually link to Conningbrook Lakes Country Park to the south via a proposed new footbridge over the railway, ensuring people living at the development and in the surrounding community can spend time in these natural areas.
With the first residents moving into their new homes in early 2024, and a new school and community centre planned, Conningbrook is taking shape as a vibrant new neighbourhood.
The first phase, Crown Hill View, is on sale now, offering people the perfect life balance, within commuting distance of the capital and south coast but with green space on the doorstep and views of an area of outstanding natural beauty.
A collection of three, four and five-bedroom homes is priced from £400,000.
