Wendover HS2 Mitigation Action Group

HS2 plans are going to create increased flooding !

Hampden Pond – when full

Hydrogeology Update

WHS2 have been highlighting for some time the devastating effect of the excavation for the ‘Green Tunnel’ and ‘Cutting’ to the north of Wendover.

The excavation will cut through the Coombe Hill aquifer, resulting in irreversible damage to our surrounding environment. The aquifer is charged up in winter and releases water during the summer through our local springs - hydrogeology is the science behind this.

HS2’s plan will effectively create a new ditch, with the trains being up to 10m below the groundwater level. At some point later this year, HS2 will start excavating and if the design is not correct, the damage will start.

The expert reports we commissioned in 2013 showed that the springs that feed the Wendover Arm Canal and the Weston Turville Reservoir Site of Special Scientific Interest (SSSI) are likely to be starved of water and will be irreparably damaged as a result. The diverted water will flow down Stoke Brook towards Stoke Mandeville and is likely to result in flooding in Aylesbury. The quantities are large, up to 30 million litres a day on average – that’s the equivalent of 12 Olympic-sized swimming pools every day!

For several years, we have been engaged with the Environment Agency (EA), HS2 and their contractors EKFB on this matter. Despite our water level measurements, reports, and the various ground investigations, very little has changed. Whilst HS2 now state that a problem exists, EKFB have told us that their current design does not incorporate the basic mitigations we would expect - such as lining the cutting to prevent water flooding the track!

EKFB are now carrying out some pump tests to measure the aquifer properties and we await the results. Our hydrogeology expert is not convinced that the tests are sufficient, so we have requested more detailed technical information so that a proper impact assessment can be made. So far HS2 have avoided responding but we have strong support from our MP Rob Butler who (like us) will not give up.

WHS2 Mitigation – Flooding Solution

In the absence of a tunnel underneath the aquifer, (which most acknowledge is the best solution) we need a technical solution which allows the water to continue to cross the railway line, without flooding the track. The solution is in the form of an inverted swimming pool (or tanking) to seal the Green Tunnel and the Cutting.

WHS2 are promoting a “Retained Cutting” configuration (see picture below). This has the added advantage of substantially reducing the noise impact to Wendover by putting an equivalent 10m high-noise barrier by the track. As it would be below ground level it also reduces the visual impact. We estimate it will save HS2 in the order of £25m. This solution has the support of the Wendover Parish Council, our local Bucks

Councillors and our MP. The Chilterns Conservation Board also share our concerns and support our calls for the retained cutting solution to be fully considered by HS2.

Help us to do what’s right for Wendover

Buckinghamshire Council have the critical role of reviewing the “Schedule 17” design submissions which are due shortly. Based on the lessons learned from Hillingdon Council’s challenge to HS2, our aim is to raise awareness and support the Council with the technical facts and questions needed to challenge the HS2 design.

We are supporting our BC Councillors in taking this up as a priority issue with the BC planning team who will undertake the review, by ensuring they are aware of our local issues. We are very concerned that if Buckinghamshire Council and the EA do not demand adequate mitigation in the EKFB design submission (schedule 17) we will lose the opportunity to protect the reservoir and the canal forever. Worse, they will leave households in Stoke Mandeville & Aylesbury to face more flooding.

You can support us by writing to our Councillors www.buckinghamshirecouncil. gov.uk or posting your thoughts on our website www.whs2.org or social channels.

Doing what’s right for Wendover