MARK OLDROYD/ARENA
Methane has the
power to blow up
a house, yet not all
homes are built to
withstand the gas.
Paul Humphries
reports
It could blow up a home at the flick of a
switch. Highly explosive methane can seep
from disused coal mines and former landfill
sites into homes built back when the
housing sector knew little of the dangers it
could pose.
And there is evidence that, even when
planners and builders knew of the dangers,
some housing developments did not put
the proper safeguards in place. So should
today’s landlords be worried? The short
answer is no one knows quite the level
of danger methane poses. It is almost
impossible to predict where and when the
gas will escape from old mine workings,
and scientists admit they are still learning
how methane travels through the ground
from former landfill sites.
What is certain is that many homes built
before 2000 could be at risk because it
was only then that building regulations
addressed the methane problem.
Good practice in the 1990s was to
ventilate the ground around buildings and
place a membrane under homes to stop the
gas seeping into the footings – but this did
not always happen. And safety work on old
housing stock has only been undertaken
when there has been a direct threat.
Alarm bells started ringing back in
1988 when the old Derbyshire pit village
of Arkwright had to be demolished and
rebuilt on safe ground after it was found
that methane from a former coal mine had
seeped into almost all of the village’s 200
terraced houses. That was a warning to
planners and builders that the closure of the
nation’s pits would put at risk homes built
anywhere near a seam of coal.
If they didn’t take heed of Arkwright,
they had other chances to learn the lesson.
A year later, a few miles from the village,
a detached house in its own grounds was
demolished by a gas blast when methane
entered the home and was ignited by
the simple act of a central heating timer
switching on.
In Barnsley, on a council estate built in
the 1940s, homes had to be evacuated
when flames were seen shooting up the
side of a house. Investigations revealed
methane from a disused mine had
infiltrated houses across the estate. During
the 1990s there were reports of escaping
methane from most of the UK’s coalfields.
In Rotherham, the gas was found on
a 1950s council estate. It was believed to
have come from a mine that had been
closed for almost 30 years.
Rotherham Council says monitoring
is continuing after the discovery in the
Kimberworth Park area of the town in the
early 1990s.
‘The problems were caused in that case
by mine workings and much remedial work
was carried out jointly by the council and
the coal authority,’ says a spokesperson.
‘The coal authority undertook a number
of measures to address the problem and
is undertaking ongoing monitoring.’
But it isn’t just methane from coal
mines that has created a threat. Landfill
sites produce vast quantities of the gas
and although these tips are ventilated to
release the methane safely, there is no
foolproof system to prevent it ‘migrating’
away from the site.
In the village of Loscoe, again in
Derbyshire, methane travelled laterally
through the ground from a landfill site,
seeped into the basement of a bungalow
and exploded.
There may also be relatively new
developments, both public and private,
where membranes have never been
fitted. For example, on a private estate
in Barnsley, built near the affected
council housing, some of the homes had
membranes fitted and others didn’t.
This only came to light when the new
residents heard of the problems with the
council houses and hired an independent
consultant.
Families on an estate in the Cheshire
town of Leftwich (see box overleaf) have
➔ Continued on page 24
Close
encounters
22 Inside Housing 16 February 2007
A detached house in
its own grounds was
demolished by a gas
blast when methane
entered the home and
was ignited by the simple
act of a central heating
timer switching on
16 February 2007 Inside Housing 23
How double death riddle revealed a gas risk
It took two coincidental tragedies for
residents of a Cheshire housing estate
to discover that their homes were under
threat from methane.
First, the death of 19-month-old
Rebecca Watts in 2004 and then the
death of Sharon Pymer, who was 18
months old, a year later. The girls lived
back-to-back in houses owned by Muir
Group on the Muirfield Close estate in
Leftwich. Both died from a rare form of
leukaemia.
There followed a lengthy investigation
by council officials, the Health Protection
Agency and doctors, to see if the deaths
were linked.
Soil contamination experts were
also brought in. It was this team that
discovered – unconnected to the girls’
deaths – that the estate was at risk of a
methane explosion.
Investigators found that the houses
were built on a former landfill site in the
early 1990s – before strict guidelines and
planning consents governing ground
contaminants, such as methane, were
in force.
Rupert Adams, principal
environmental health officer at Vale
Royal Council, says: ‘The site wasn’t
vented [properly] because it was prelicensing and therefore not controlled
in respect of venting. Developers
were aware of gas issues and acted
accordingly with a range of gas control
measures in their buildings, including
venting.’
Those measures included fitting
membranes under the homes to divert
any unwanted contaminants coming
from the soil, including methane. But
these membranes had not been fitted
properly.
Methane could have been
entering the homes for
more than 10 years
without anyone
knowing. The
MARK OLDROYD/ARENA
We can’t say that we have eradicated the dangers, but those dangers that exist
have been recognised. We fully understand that contaminated land is an issue
only recently discovered that the membranes under some
housing association homes, built in 1994, had not been
fitted properly and their homes were at risk from methane
from a former landfill site on which the homes stood. This
was only detected when soil tests were done following the
death of two toddlers from neighbouring families who
both died within a year of each other from a rare form of
leukaemia.
Sam Scott, director of housing services at Muir Group,
which owns the homes, says: ‘As part of the ongoing tests
on the land, environmental consultants carried out checks
and found that membranes in three of the properties were
not working correctly. We have employed environmental
experts to decide on, and implement, the best option for
remediation.’
Phil Crowcroft from Environment Resources
Management, which Muir Group called in, says:
‘Thousands of homes across the country are built on
brownfield sites with similar ground conditions and
the installation of gas membranes and vented voids is
standard practice. The proposed remediation works will
bring the Leftwich homes up to an appropriate standard.’
For the past 10 years, Derwent Living has operated
a 24-hour methane monitor on one of its housing
developments in Leicester so that any emissions from a
former landfill site can be detected immediately. This is
on top of other safety measures, such as membranes and
ventilating bricks in the properties.
Chief executive John Martin says: ‘The methane
monitor will continue to operate for the full life of the
housing development. Methane can be a big problem and
we have come across sites so badly polluted with the gas
that we have had to turn them down.’
Experts agree that building regulations and safety
procedures have advanced dramatically since the events
of the 1980s and 1990s, but they also admit we still do not
know the full extent of the dangers from methane.
The problem of radon, the radioactive gas that forms
naturally in the ground, has been well documented
and areas of the country that are at risk have been well
researched and mapped out. But there have been only a
handful of scientists, planners and engineers that have
attempted this with methane.
Five years ago, the British Geological Survey
campaigned for methane to be mapped out like radon
and wanted local authorities to take advantage of the
expertise offered by the BGS and others in predicting
where methane could cause problems.
There was little take-up despite the last Conservative
government commissioning a report into the threat posed
24 Inside Housing 16 February 2007
by mine gas emissions. The report was published in 1996
reminding local authorities and developers of their legal
duties and of what needed to be done before planning
consents were granted.
But since the mid-90s much progress has been made
in understanding and addressing the problems posed by
methane. There are now strict technical guidelines on
emissions from the Environment Agency and, following
the new building regulations in 2000, the government
included methane when it updated guidelines on planning
and pollution control in 2004.
‘Yes, there have been some important developments
in the last 10 years, much of which can be seen in the
2004 Housing Act which did away with the old fitness
standard where something was either judged black or
white,’ says Andrew Griffiths from the Chartered Institute
of Environmental Health. ‘Now we have a proper ratings
system and it means these new procedures give us more
powers to address the problems such as methane.’
What the BGS would like to see is more
understanding of how the problems with
methane arise. Principal scientist Dr
Gerry Weatherall admits there is still
much work to do on understanding the
problems landfill sites throw up.
‘We are interpreting the complexity
of the geology alongside landfill sites,’
he says. ‘And we’re still looking to
understand how gas migrates.’
He quotes the Loscoe explosion as an
example. ‘This house wasn’t alongside
the landfill site, but well away. The site
was bounded by a natural barrier of clay
which should have protected the properties
adjoining the landfill, but the gas migrated laterally,
found a gap in the clay that had naturally eroded,
seeped into the basement and was then ignited. How was
anyone to know that was going to happen?’
Mr Griffiths is also cautious. ‘We can’t say that we have
eradicated the dangers, but those dangers that exist
have been recognised,’ he says. ‘We fully understand
that with existing housing contaminated land
is an issue, whether with methane or other
contaminants.’
Despite local authorities’ and social
housing providers’ best efforts to
deal with the problem, there are
no guarantees that their remedial
measures will prove to be
sufficient. Only time will tell.
homes are now being fitted with new
membranes and methane alarms.
Both the investigating team and local
residents have accepted that neither the
council nor Muir Housing can be blamed
for the membranes not being fitted
properly. To date, no link between the
girls’ deaths has been
established.