PC: Institution of Civil Engineers (ICE)
Dearne Reach, a 4.3-hectare integrated constructed wetland in Clayton West, Huddersfield, treats wastewater and storm overflows with plants rather than pipes. A traditional solution would have needed 7,000 m³ of stormwater storage and a 4.5km pipeline, according to the Institution of Civil Engineers (ICE). Instead, over 350,000 plants from 52 species, set in 13 cells, take nutrients from the water to help improve quality along 4km of the River Dearne. Mott MacDonald Bentley delivered the £14 million project for Yorkshire Water in nine months. ICE reports a 60% reduction in embodied carbon and a 40% reduction in operational carbon across its lifecycle.
ICE states that a traditional “grey” infrastructure solution would have required 7,000 m³ of stormwater storage and a 4.5km pipeline to divert treated wastewater downstream. The wetland instead uses natural processes to reduce pollution, particularly of un-ionised ammonia, which the page describes as highly toxic to aquatic life, and to improve storm flow treatment, according to ICE.
The source says that at 4.3ha this is currently the largest integrated constructed wetland for storm treatment in the UK. The project won the Centenary Award at the 2026 ICE Yorkshire and Humber Awards, according to ICE. The 52 plant species sit in 13 cells, and over 350,000 plants adsorb nutrients from storm overflow discharges and from wastewater flowing out of the Clayton West wastewater treatment works, according to ICE. ICE reports that the project achieved a 60% reduction in embodied carbon and a 40% reduction in operational carbon across its lifecycle. The site presented high groundwater levels and difficult ground conditions in the form of sandy-gravelly clay, alongside a need to reuse more than 13,000 m³ of excavated material, according to the source.
ICE adds that “adsorb” means the nutrients attach to the plants rather than being absorbed. The source says traditional ICWs are only effective when there is a constant flow of water, whereas this design can handle the unpredictability of stormwater discharges. Solar-powered monitoring equipment controls water levels and measures flow rates, and it collects data on water quantity and quality that will support future development of similar nature-based solutions, according to ICE. ICE says groundwater management techniques allowed cell heights to be increased, which improved the balance between excavation and fill material and reduced the need to import material. Roadcem soil stabilisation technology replaced traditional concrete access roads, reducing the need for imported aggregates and cutting carbon emissions, according to ICE.
ICE reports that Mott MacDonald Bentley was principal designer and contractor, Yorkshire Water was the client and Stantec produced the outline design. The wetland is divided into multiple cells, each designed to hold water for longer and remove pollutants more effectively. ICE states that the wetland was specifically designed to treat intermittent storm overflows. ICE lists several further measures taken during construction. The amount of bypass pipework was reduced through maintenance planning, lowering the carbon footprint. A geosynthetic clay liner was used instead of more carbon-intensive plastic alternatives to provide impermeability and protect groundwater.