In June 2022 HS2 contractors Align Ltd, building the Colne Valley Viaduct, submitted plans to dewater cofferdams along the line of the Viaduct as they have found polluted water in the jetty piers for the haul road.
Several of the polluted cofferdams are only 30 metres away from the Blackford water source.
A cofferdam is an enclosure built within a body of water to allow the enclosed area to be pumped out.
While the haul road piles were sunk into the aquifer to around 30 metres, the piles for the Viaduct will be much deeper up to 70 metres. The fear is that dewatering can induce drawdown which can cause underground water pollution (from the landfill site) to migrate to towards the viaduct. If this happens there will be permanent damage to the Blackford water public water source.
The cofferdams would normally have been dewatered into the local environment but now they are polluted, it is more problematic. There is a new waste water pipeline planned.
To avoid permanent damage to the Blackford source, HS2 works should be paused and the cause of the water pollution identified and made public. It is illegal in the UK to deteriorate a public water source.
In 2019 Sarah Green and Niki Samuels spoke with Nick Hurd MP and Jane Palmer Conservative Councillor, about our concerns that the water pollution from Newyears Green landfill site would be spread across the valley to the Blackford source on Moorhall Road. Before HS2, the Blackford source was drawing 20 million litres a day of good quality public tap water which did not need treatment or additional purification.
As a result of these legitimate concerns, Nick Hurd received a letter from Allen Cook (Chair of HS2 Ltd), see attached.
The letter stated: “There will not be any dewatering of the chalk aquifer during piling so there is no potential to induce drawdown that would cause exiting pollution to migrate towards the viaduct”.
Jenny is a Green Party politician asking questions in the House of Lords on behalf of the people of Hillingdon, working to protect our drinking water.
It’s now time to halt the works and check whether the Colne Valley water sources can be saved.