A WYE Valley firm has been called in to help a £2.5 billion underground development in Sweden.

Water treatment specialist Siltbuster, based in Monmouth, has been contracted to help deal with the huge volumes of potentially polluting water produced by tunnelling and concreting beneath the city of Gothenburg as part of its 8km metro rail line extension.

The West Link scheme, which is due for completion by 2026, includes a 6km railway tunnel and the creation of three new underground stations, and will increase accessibility to Gothenburg, boost capacity and improve travel times.

Siltbuster’s role is vital as the link is being developed next to the biggest amusement park in Scandinavia, The Swedish Exhibition Centre, the World Culture Museum, Gothenburg World Trade Centre and ice hockey and football stadiums, said a company spokesperson.

The contractors, Nordic Construction Company (NCC), are excavating through granite, limestone and clay for the tunnel and stations, and the site’s surface water runoff and ground water can come into direct contact with the exposed soil, creating waters with a high concentration of suspended matter, including fine, slow-settling, clay particles.

The spokesperson said: “If a significant amount of this material enters nearby drains and watercourses, it can block the gills of fish and smother aquatic plants and invertebrates, starving them of light and oxygen.

“The extensive concreting works during the construction phases will also create highly alkaline, cementitious construction waters with an elevated pH of 12-13 – akin to oven cleaner; again highly polluting to the environment if left untreated.

“For the Gothenburg Metro, Siltbuster’s experts recommended the use of three integrated iHB40Rs treatment units which remove the solids to less than 25mg/litre of suspended solids, and then neutralise the pH so that the water is pH 7 neutral.”

Kristian Downs, Siltbuster export sales manager, said: “With the construction work taking place in a high profile, densely populated, built-up area, and with a main highway linking Malmo to Oslo running nearby, space is at an absolute premium.

“There’s limited room on site for additional plant and equipment. That’s why our iHB40R ticks all the boxes. It’s a highly effective, easy-to-use treatment solution, that’s agile and space efficient.

“To be involved in yet another prestigious international project is a great endorsement for the expertise of our team, the robustness of our systems, the size of our fleet, our technical back-up and our growing reputation within the world’s construction sector.”

Founded in Monmouth in 2003, Siltbuster is recognised as a world-leading authority on water treatment.

Its systems are used in more than 30 countries and have been deployed on a range of international rail and tunnelling projects, including the Grand Paris Express (GPE), the Doha Metro in Qatar, the Northern Line extension, Crossrail, Thames Tideway Tunnel and Stuttgart S21.

Last year, the company moved a few hundred yards from its former base into a purpose-built £4.3m HQ on Wonastow Road.