Wetlands are valuable features in our landscape, providing a number of functions for people and wildlife. They help to secure and enhance the water quality, provide food and essential habitats for numerous wildlife species and maintain surface water during dry periods.
In early autumn 2018, Ramboll was appointed by Woolston Eyes Conservation Group (WECG) on behalf of the Royal Society for the Protection of Birds (RSPB) to develop a concept design for two new wetlands covering a total area of 38 hectares in Woolston Eyes Nature Reserve, which lies to the west of Manchester. Our concept design, associated supporting assessments and documentation are being used to apply for funding from Natural England to carry out a detailed design and subsequent construction of the new wetlands.
A protected site and rare breeding ground
The Woolston Eyes Nature Reserve comprises four silt lagoons (beds) adjacent to one another in an east-west alignment sitting south of the River Mersey and north of the Manchester Ship Canal (MSC). The MSC has been regularly dredged since the start of the 20th century, depositing dredged material across the four beds in a rotational manner. All four silt lagoons are designated by Natural England as Sites of Special Scientific Interest (SSSI) for wintering waterfowl and breeding waterfowl assemblage. In addition, the reserve comprises one of the two principal breeding sites in Great Britain for black-necked grebe.
A site rich in wildlife
The site supports nationally important wintering numbers of teal and shoveler, while the willow scrub found in all four silt lagoons supports one of the highest densities of willow tit in the United Kingdom. Bed 3 and the north-western part of bed 4 have already been developed into wetlands for the benefit of biodiversity (of birds in particular). It is proposed that the two new wetlands (cell 1 & 2) are developed within bed 4.
- Considering the unique nature of the site and its importance for various wildlife species, our role focused on:
- Determining the annual ‘water budget’ for the proposed wetland cells by considering all relevant hydrological processes and effect of the annual change in water storage, which essentially identified whether the concept was feasible from a hydrological point of view.
- Assessing the different drainage solutions to identify the most suitable for the rotational dynamic management of water levels within the proposed wetland cells, including drainage to the River Mersey.
- Undertaking a ground condition assessment in spite of very limited information available in the area.
- Developing a 3D digital terrain model to assess earthworks options to incorporate ‘mass balance’ in order to retain all material on site.Developing a concept design for the creation of the two wetlands and determining key features including bund height, typical water depths, general desired pattern of islands and submerged islands and components of the proposed drainage and water management systems.
- Quantifying the scheme’s outline cost plan.
- Health and safety risk assessments for CDM regulations including a pre-construction information pack.
Through a range of services, Ramboll has produced an appraisal and design that enables the client to apply for funding for the implementation of works to create an enhanced habitat encompassing an area of 38 hectares. This significant area will aid in creating increased biodiversity for both aquatic and terrestrial ecology with the overall goal of enhancing habitat for wintering birds.
Experience in wetlands remediation
Our work on this project follows on from our appointment last year to work on the award-wining Wathamstow Wetlands scheme, where we provided environmental, hydrological, engineering and geotechnical services for the development of new reed beds at Europe’s largest urban wetland nature reserve.