The group constructing the HS2 line from London to Birmingham has invested £100 million in water filters and pumping equipment in response to concerns that the project may contaminate water supplies.
The rail route passes under the Chiltern Hills, home to biodiverse chalk streams, which water companies have committed to protect and enhance by cutting abstraction.
There were fears that chalk dust from the hills could leak into aquifers as the tunnels were dug and would clog and damage pumping equipment.
The Environment Agency and Affinity Water raised these concerns but both have now signed off the tunnelling works after HS2 agreed to fund £100 million worth of added capacity to local water treatment plants to maintain the quality of local supplies.
Senior project manager for HS2, Mark Clapp, said “a lot of science” went into ensuring the water supplies would not be at risk.
New filters and pumps will be added to three nearby water stations to prevent them from being clogged by chalk dust generated by the 2,000-tonne tunnel boring machines (TBMs) as they dig through the Chilterns. Capacity will be increased to allow a fourth pumping station to be offline at the peak of the digging.
Clapp said the machines can pump quick-drying mud into any voids encountered during tunnelling to act as a seal, preventing leakages of chalk dust.
Conservation group the Chilterns Conservation Board said HS2 would cause irrevocable damage to the natural beauty and tranquillity of the Chilterns Area of Outstanding Natural Beauty (AONB). Not only, the board claims, will HS2 destroy wildlife, habitats and ancient woodlands, it will place unprecedented demand on the fragile chalk aquifer, with potentially devastating impacts on Chilterns’ chalk streams – a globally rare habitat that is home to some of our most threatened animals and plants and the source of drinking water for almost one million people.
Additionally, the group said the rich archaeological legacy of this protected landscape, including fragile prehistoric earthworks, will be lost to future generations.
Water companies in the southeast, where 80 per cent of the world’s chalk streams are found, committed to cut abstraction, reduce pollution and restore these ecologically critical waterways.
Affinity unveiled a five-year plan to improve flow and biodiversity of streams in its own catchment and is working with local environmental groups and NGOs to improve the health of waterways.
In September it stopped abstracting from the River Chess and began work to cease abstraction from other streams by 2024.