Chilterns Conservation Board’s statement on the Little Missenden sink hole above the HS2 tunnelling operations

The CCB and others have warned for many years that the unstable nature of the fractured chalk meant that HS2 tunnelling operations might lead to long term permanent damage to the chalk aquifer, River Misbourne chalk stream, the wider landscape and wildlife living above the route.

For example, geologists, including Dr Haydon Bailey, highlighted their concerns over 13 years ago in a report published by the Chiltern Society in August 2010 – just six months after the government announced its preferred route for HS2. At the time, Dr Bailey’s report summarised potential impacts including:

1. long term damage to the chalk aquifer;
2. pollution of the main water supply system for the north western Home Counties area and potentially further into north London (a point emphasised by Dr Bailey when he appeared before the High Speed Rail Select Committee in July 2015);
3. running the risk of serious ground collapse in areas with deep sections of weathered chalk;
4. depressing the water table in the Misbourne valley, resulting in
   • the total loss of surface flow in the Misbourne River system, and
   • the destruction of the adjacent habitats
5. the aesthetic loss of the Misbourne River and its replacement by a dry valley.

Clearly point 3, the serious ground collapse, has now occurred.

Despite confident assurances by HS2 Ltd throughout the Select Committee process proceeding approval of the HS2 Bill, and repeated assurances by their contractors since, the Chiltern Society, the Chilterns Chalk Stream Project, the Chilterns Conservation Board, and many local groups and individuals have continued to express their concern that tunnelling operations will be extremely damaging. Unfortunately, our fears appear to be justified and we will now be urgently seeking answers and for appropriate action to be put in place to safeguard the landscape, wildlife and residents of the AONB.