29-Jul-2020

Pollution of the Misbourne

EA report obtained under FOI

This FOI request (eventually) obtained the report of the EA inspectors into the pollution incident; its 'Stratification' - nothing to see here ...

"Not Us, Guv" - EA clear HS2

The Environment Agency has cleared HS2 contractors of any wrongdoing after reports that a lake in the Chilterns had become polluted.Inspectors from the Environment Agency visited the site (late) on Saturday following local complaints that the water had been polluted by HS2 contractors drilling near to a chalk aquifer.
However, a spokesperson for the Environment Agency confirmed that its investigation of the lake “found no sign of pollution”.

An Environment Agency spokesperson added: “Pollution incidents can cause distress to local communities, reduce water quality and put precious wildlife in danger.
“We take all claims of water pollution very seriously and will always investigate any such reports.” in order to clear HS2 ?
(New Civil Engineer)

31-May-2020

Ground Investigation causing Turbidity at Shardeloes Lake

Fusion or Align have been working on the Southern side of the Misbourne, near the Little Missenden Vent Shaft site, for some weeks -

The works beside the Misbourne are conducting Ground Investigations along the line of the tunnel, and 'Pump Tests' - but don't appear on the Little Missenden works notification. Maybe too embarrassing, still carrying out ground investigation while choosing names for the Tunnel Boring machines ? Six boreholes have been drilled, two of which pass diagonally under the lake. The works were carried out without requesting permission from the landowner, and with no offer of compensation.

On 29th May, the River Chess Association received reports of cloudy water in Shardeloes Lake -

although the water flowing into the lake was clear. This was investigated, and reported to the Environment Agency - see Post for more information, and more photos.

The next day (30th May) a drone flight revealed the source of pollution (which had declined a little) -

A white plume of suspended chalk particles, not far from the HS2 borehole. (See this post for more pictures) A complaint has been registered with HS2 regarding pollution of the lake, and it has been reported to the Environment Agency ( that fearless defender of the Natural World).

Consequences

While the immediate consequences of this incident are unlikely to be severe,  it does illustrate how fragile the aquifer is. If a single borehole can produce this effect, what will happen when two 16m diameter tunnels are driven around 10m below the lake bed ? The plan on the right shows the course of the tunnels as they run under the lake, close to the 'White Plume' in the picture above.

While the lake can cope with a limited amount of turbidity, the boreholes used to abstract (too much) water from the aquifer cannot. Ultra-violet radiation is used in the sterilisation process, and since this does not penetrate turbid water, the process fails. Works currently underway in Amersham (at the water works, opposite Tesco car park) are to provide a water clarification plant to treat water pumped up from the borehole at Chalfont St. Giles.

The risks arising from driving a tunnel under the aquifer have been raised with HS2 on numerous occasions - for instance at the Chess Association meeting in 2018 - and Affinity Water have an unlimited indemnity to compensate them for any interruption to their supplies. The chances of this being invoked are now greatly increased.