Europe’s largest urban wetland nature reserve, in Walthamstow, London.

In 2017 Walthamstow Wetlands was officially opened to the public, offering an abundance of wildlife just 15 minutes from central London. With improved visitor facilities and free entry to the wider public, it is also bringing much greater visibility to the 150-year-old site, in an area of London that has historically been deprived and underdeveloped.

As well as a nature reserve with footpaths and cycle tracks twisting between the fully operational reservoirs, the site encompasses the redesigned Engine House with a visitor centre, café and re-built tower for nesting swifts and roosting bats. The Grade II listed Coppermill Tower meanwhile offers panoramic views of the city.

Plans to transform the site began in 2012 to create a wildlife-rich reserve and rural escape for residents and visitors. A significant challenge was Thames Water’s requirement to dredge two of the three reservoirs that were the focus of the reed bed creation, used by Thames Water as settlement lagoons for the copper mill water treatment works. To remain operational, the reservoirs have to be dredged every five to seven years and, prior to Ramboll’s involvement, over 10 years had passed meaning the water depths had been reduced, with an associated impact on settlement capacity and water flow.

Employed by the London Borough of Waltham Forest, we provided environmental, hydrological, engineering and geotechnical services for the scheme, which delivered 1.8 hectares of new reedbed habitat, which now require less frequent dredging and improves purification capacity of the wetlands. We prepared a hydrological and geotechnical design together with a dredging specification to make way for the new wetland area whilst allowing for the continuous supply of London’s potable water. Our team also reviewed specialist ecological survey data, prepared a draft design of reed bed planting plots (including reed stock, species mix and plant specifications) and prepared biosecurity notes to evaluate the presence of invasive species on or around the site during the reed bed creation works.

We also supported the client with the completion of the final design for tender, prepared ecological specifications for the contractor’s tendering for the project and provided a client’s representative for the construction process.

To create the reedbeds, a total of 619 metres of retention structures were built. A timber post and geotextile system was used, enabling us to use the 9000m3 of excess sediment from the dredging process, instead of stone filled gabions. This reduced the costs to more than half, avoided large amounts of material to be imported to site, saved 600 truck movements, and an estimated £1.5million in landfill disposal costs and tax.

The multi-million-pound development was funded by the Heritage Lottery Fund, Thames Water, the London Borough of Waltham Forest and the London Wildlife Trust.