HS2 at risk of collapse in former mining area

Andrew Gilligan
January 29 2017, 12:01am,
The Sunday Times

A proposed section of the HS2 rail line, to be built over a former
mining area, will be at “high risk” of ground collapse, according
to a report obtained by The Sunday Times.
The £56bn network will cross part of Cheshire undermined by salt
mining and notorious for subsidence. A report on “salt-related
ground stability” by HS2 Ltd, which oversees the project, says the
line will also cross Britain’s biggest active salt mine, at Winsford,
where digging is planned to extend its workings.
The report warns of “the potential for the rapid development of
significant movement” in this area under the weight and vibration
of trains, “with a consequent risk rating as high”.
It identifies five more salt-mining or brine extraction sites near the
town of Lymm where it classes the risk as red, the highest, and 14
more locations where it is amber, the second highest.
Antoinette Sandbach, the Tory MP for Eddisbury in Cheshire, said
the line was being built in “entirely the wrong place”.
Salt mining, which has gone on in Cheshire since the 17th century,
involves hollowing out vast caves, many not far below the surface.
Buildings in the area suffer from major subsidence and have to be
The proposed route has been changed once to avoid running over
massive underground caverns which could cause a “catastrophic
ground loss”, the report says. The new route will require the
closure and rebuilding of the A556, one of Britain’s most
congested roads, as well as miles of new embankments and
viaducts, adding up to £750m to the cost.
However, the new route may be even worse than the previous one,
according to the HS2 report and a study by the consultancy
TerraConsult for the campaign group Mid Cheshire Against HS2.
TerraConsult says the new route carries an “increased risk of
subsidence” because the length of track on “higher-risk” surfaces
has risen by more 3,000ft. It says the increased use of
embankments is a “particular concern”, adding, “A higher
embankment increases the applied loads . . . If the ground below is
not strong enough, there will be a slope failure.”
The consultants attack as “highly disingenuous” a claim by HS2
that the route has been changed to “minimise the risk of
subsidence”. Even the HS2 report, which has not been published,
admits a “high risk” on several sections of the new route.
Critics say the new embankments will tower up to 56ft over the
flat countryside, creating an eyesore.
Sandbach said: “HS2 appear to have ignored the evidence but it is
not good enough to simply carry on regardless.” She said that an
alternative route along the M6 would be cheaper, quicker and
The Cheshire section is part of HS2’s second phase, between the
West Midlands and Manchester. The first section of the line, with
225mph trains linking London and Birmingham, is expected to
win parliamentary consent within weeks.
HS2 said: “Development of HS2 is a thorough and detailed
process, as part of which we commissioned this report . . . We are
now consulting on the route through this part of Cheshire.”