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Worsbrough Reservoir wall rebuilt with biodiversity-enhancing rock bags

Worsbrough Reservoir wall rebuilt with biodiversity-enhancing rock bags

A new bankside wall using material ideal for aquatic insects has been installed along the north and south shores of Worsbrough Reservoir in Barnsley to replace the former, failing wall.

The metre-high bankside wall around the reservoir is a favourite place for local anglers. The wall had become unstable as wave action undermined the foundations, so contractor Balfour Beatty removed and rebuilt it with the help of RSK Group company Salix River & Wetland Services, using pre-filled rock bags.

Salix Project Manager Chris Smith said: “We’ve built the new wall using pre-filled Rock Roll Mattresses, rather than the traditional gabions or concrete piling. The Rock Rolls use stones measuring around 40–80 mm in diameter, where traditionally 100–150 mm stones would be used. The smaller stone encourages aquatic invertebrates – a major source of food for many freshwater fish – to settle in the spaces between rocks. In the end, this means a more natural bankside for local wildlife and a boost for local anglers.”

Salix and Balfour Beatty spent 12 weeks on-site. The reservoir was closed for public access from 27 May 2023. The location made equipment access a challenge, and the team had to build an access track in, which was then removed in sections as they worked their way back out.

Chris said: “Scour or soil erosion is a major concern in the water sector. Because it’s a natural process, working against it with traditional hard-engineering solutions like rock armour or sheet piling will only get you so far. By working with nature, using more sensitive solutions that are less impactful and allow nature to thrive, you can protect against erosion and also help nature.”

Built in 1793, the 60-acre reservoir holds 266,000 m3 of water, about the same amount as used by over 2,200 homes in a year. It is located inside the 240-acre Worsbrough Mill Country Park, home to a wide range of wildlife and habitats and criss-crossed with pathways for walkers, while the reservoir itself is also home to a continuous stock of carp and other angling species, making it a popular fishing spot. An event to mark the reopening for angling and walking is set to take place on the 22nd of January.

Balfour Beatty spokesperson Chris South said: “The Rock Mattresses arrived on site pre-made which, coupled with the fact you could tie them together, meant that wagon loads to site were reduced. They were quicker to install than traditional faced gabion baskets and they produce a natural look, which was in keeping with the surroundings of the SSSI site.”