4 minute read
Crumpmeadow
Cinderford, England, United Kingdom
Constructing wetlands to improve local biodiversity. Five interconnected ponds between 2.6 and 5 meters deep promote biodiversity and reduce surface water runoff into Cinderford Brook at Crumpmeadow wetland near Gloucester in southwest England. The ponds’ variously angled slopes and internal shelves promote a more natural, diverse habitat for insects, amphibians, and reptiles that are of conservation concern. Initiated in 2019, the project began when regional water company Severn Trent Water contracted Mott MacDonald to develop feasibility and concept designs, and pond construction began in 2021. Challenges faced included the presence of protected great crested newts (Triturus cristatus), eels in Cinderford Brook, the lingering environmental impacts from the operation of old coal mines in the area, and the potential for high groundwater levels. Ground investigations, including trial pitting, boreholes, soil sampling, and a geophysical survey, were completed to understand the risks from historical mining. Newt fencing was installed, and resident amphibians and reptiles were relocated to a nearby woods. Afterward, the area was seeded with native wildflowers and planted with trees. Mott MacDonald Bentley and Severn Trent Water were awarded the Institute of Civil Engineers West Midlands’ 2022 Team Achievement Award for their collaboration with project stakeholders comprising the Gloucestershire Wildlife Trust, local landowners, Forestry England, and the Forest of Dean District Council.
Article Cover: One of the five new wetland ponds and connecting channel. (Photo by Helen Leyshon, Mott MacDonald Bentley)
Producing Efficiencies
Silt fencing along the site perimeter and silt socks used where groundwater was pumped from excavations protected water quality in Cinderford Brook. Solar pods, not diesel generators, powered the worksite, saving about 1,400 liters of fuel and avoiding noise pollution and nine tonnes of CO2 emissions. Hybrid excavators were used, and excavated soil was kept on site as much as possible to create bunds with southfacing slopes, designed to provide suitable habitat for reptiles, invertebrates, birds, and small mammals and areas for planting of local species. The project used only recycled stone, and at the end of construction, to reduce single-use plastics, fencing to protect the great crested newt was removed for use on another project.
Using Natural Processes
Vegetation strips along the edge of the worksite protected the surrounding area from on-site activities. Plant species well established in the area—including march violet (Viola palustris), cowslip primrose (Primula veris), and water mint (Mentha aquatica)— were sown to encourage habitation by various invertebrates and birds. The ponds were lined with clay excavated on site, not geotextile, and excavated wood and stone were used to make hibernacula (refuge spaces for hibernation). The wetlands attenuate runoff into Cinderford Brook and function without pumps, so their operation is low carbon. By avoiding existing high-priority grassland , the project raised the biodiversity value of the rest of Crumpmeadow.
Broadening Benefits
This project spawned numerous community and educational events, including information sessions, community drop-ins, and a poster competition, to promote local ownership and support for this and other environmental efforts. Brownies and Girl Guides planted trees and other vegetation and built “bug hotels” at an educational planting and engagement event commemorated by a special Brownie badge and a plaque. Cinderford’s mayor planted an oak tree to celebrate the queen’s platinum jubilee. The water cycle, the importance of biodiversity, and environmental careers were discussed at the local school. Further, posters displayed at a drop-in event explained the project’s purpose and progress.
Promoting Collaboration
Extensive collaboration by the Mott MacDonald designers, the Mott MacDonald Bentley technical experts, the client (Severn Trent Water), and key stakeholders from the Environment Agency (EA) and Gloucester Wildlife Trust meant no project decision was made in isolation. The feasibility team originated the ground investigation plan, which was refined by the contractor, site manager, and ecologists, to gather the required data without ecological or environmental harm. The EA and its consultant helped to address risks to eels. Regular design packs kept the EA abreast of project progress and gave opportunities for regulator input into the design.
