Post on 26-Mar-2015
Delivering sustainable solutions in a more competitive world
Learning from experience – from Loscoe to Leftwich
VOCs and Ground GasesBrownfield Briefing Conference
November 2009
Phil Crowcroft Partner, ERM
Delivering sustainable solutions in a more competitive world
Abbeystead 1984
• Natural methane released into water supply tunnel from deep limestone geology
• Pushed into valve house by start of water pumping
• Ignition source not known, but visiting group from local community present
• 16 killed by explosion
Vent stale air to atmosphere, not building
Delivering sustainable solutions in a more competitive world
Loscoe 1986
• Inert waste landfill surrounded by housing
• Later amendments to licence allowed domestic waste to be tipped
• Evidence of vegetation dieback in surrounding lawns
• LFG migration through bedrock driven by rapid fall in atmospheric pressure (29mb in 7 hours)
• Gas entered bungalow, ignited by boiler switch
• Two injured
Houses and landfills don’t mix easily
Delivering sustainable solutions in a more competitive world
Arkwright Colliery (1988)• Village of Arkwright located in area of
mined shallow Coal Measures with significant mine gas emissions into properties
• Cost of gas protection measures high
• British Coal proposed to move village
• New community built nearby, old housing demolished
• Shallow part-worked seams then opencasted to provide revenue to cover cost of building new community
Think big!
Delivering sustainable solutions in a more competitive world
HMIP letters 1987 - 1989
• Chief Inspector of Her Majestys Inspectorate of Pollution (HMIP) wrote to all Local Authorities in 1987 asking them to identify the location of landfills in their area, and whether they posed a risk to built development
• Follow-up letter in 1989
• Boom in soil probing and borehole investigations
• Numerous sites identified where housing built on or close to landfill
• 75% of Dudley within 250m of landfill
Delivering sustainable solutions in a more competitive world
Gregson Survey 2000
0
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80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
Line 1
Delivering sustainable solutions in a more competitive world
Westleigh, Lancashire 1988
• Housing development under construction next to deep domestic waste landfill
• Boulder Clay overlying Coal Measures
• Mine shaft in housing area
• Gas seen bubbling up through puddles in garden areas of part built houses
• Building stopped, litigation followed
• Final solution involved sealing sides of landfill, deep vent trenches, sealing of mineshaft
Finished but unsold houses sold at auction for 15% below market value
Delivering sustainable solutions in a more competitive world
Country house 400m from landfill (1991)
• Methane entering basement at 11%
• Gas travel time from landfill less than one hour
• Enhance gas abstraction at landfill
• Remove floor and install venting zone and membrane in house
• Positive pressurisation
• Gas detection
• Remote dial-out and control - don’t under-estimate speed of gas movement
Substantial management commitment over long-term
Delivering sustainable solutions in a more competitive world
Clayboard 1990s
• Bishopsgate - major new development with deep basement
• Basement floor piled and void created below slab to allow for London Clay heave
• Clayboard used, comprising corrugated cardboard, which collapses when wet
• Also produced methane, and this ignited when hole drilled through slab, flash over singed hair
• Cricket ground stand – same construction, feared same problem
• Slab drilled, and methane found at high concentrations
• Clayboard tunnelled out
Beware or unexpected consequences of building products!
Delivering sustainable solutions in a more competitive world
Weston Village 2000-2002
• ICI disposal of hexachlorobutadiene (HCBD) in landfill in sandstone quarries in 1950/60s
• Testing found low concentrations in boreholes and properties near quarries
• Properties zoned by risk, green, blue and unzoned
• Whole village included in “communication zone”
• Abnormality of kidney function thought to be associated with HCBD exposure
Delivering sustainable solutions in a more competitive world
Weston Village (continued)
• ICI offered to compensate depending on risk levels and purchase most houses in village
• Offer created unexpected side effects
• Compensation for green zone (£5k) created envy from Blue (£2.5k) or unzoned (£0k)
• Those that didn’t take purchase offer found themselves living in ghost town
• Local services deteriorated as people left, despite ICI stated intent to keep village together
• But some saw the departure of local rowdies as a positive effect
Delivering sustainable solutions in a more competitive world
Weston Village - lessons
Paper on Social Impact of Land Contamination, by Barnes, Litva and Tuson (2005)
Community Liaison and Counselling Service of great benefit
Community-based chemical contamination is always a social issue
Health effects as much from worry, uncertainty and upheaval, as from actual contamination
Biggest mistake? Allowing whole village to become associated with, and stigmatised by incident
Delivering sustainable solutions in a more competitive world
School site 2007
• Part 2A investigation showed primary school partly over old gassing landfill
• Internal air monitoring showed naphthalene above background
• Various other VOCs present attributable to paint, cleaning fluids etc
Concerns included
• history of various cancers amongst staff
• presence of mobile phone mast next to school
• potential for blight of school if problem publicised
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Brewery site, London 2008 - naphthalene
• Odours detected in occupied refurbished apartments in former Brewery building
• Naphthalene measured at significant concentrations, Part 2A Determination
• Source found to be impregnated timbers encased in concrete basement floor
• Timbers removed, remedial targets were to show no residual risk
Challenge was to prove that gas reduced to below background
Measurement at the very edge of technology
[Another site recently aspired to “non-detect”]
Delivering sustainable solutions in a more competitive world
VOC plume below house 2008 (1)
• Practical issues around working in someones home
• Health and safety issues for existing subfloor void entry
• Fluctuating groundwater entering void at times of heavy rain
• VOC in unsaturated zone, and volatilises from groundwater when this rises above base of void
Delivering sustainable solutions in a more competitive world
VOC plume below house (2)
• Tracer gas system used to identify flaws in ground floor slab
• Positive pressure air system installed
• Floating membrane laid in base of void
• Insulation of floor slab above void
• Equitable payment for power requirements of blower
Delivering sustainable solutions in a more competitive world
Leftwich - Housing estate on gassinglandfill (2007 -2009) (1)
• Acute myeloid leukemia deaths linked to possible exposure to gases from ground
• Investigation revealed relatively high concentration, low flow rate methane locally
• Temporary gas detectors installed in houses whilst works progressed
• Tracer gas testing to assess effectiveness of installed gas membranes (leaked like a sieve)
Delivering sustainable solutions in a more competitive world
Leftwich (2)
• Solution included:
• removal of floors to allow inspection and clearance of existing subfloor voids
• replacement of old membrane with new, quality assured laying and further tracer gas testing
Delivering sustainable solutions in a more competitive world
Leftwich (3)
• Insertion of additional airbricks and cross venting between party walls
• removal of all waste to depth of 4 metres in gardens of six worst affected properties
• replacement with inert fill and reinstate gardens
• large scale flux box test
Delivering sustainable solutions in a more competitive world
Leftwich - lessons (4)
Lessons learned:
need for high confidence solution (simple passive)
a social problem as much as a technical one
work with the community directly affected (24 houses)
allow them to be part of the decision-making body
provide a consultant that reports to them
ensure that HPA are central to statements around health
Delivering sustainable solutions in a more competitive world
Conclusions
As knowledge improves, we revisit old issues
Can’t afford to be complacent about explosion and asphyxiation risk
Health risks from VOCs are only slowly becoming understood
Society is moving towards a low tolerance of residual risk
Social impacts will often over-ride all other concerns unless there is death or injury
Delivering sustainable solutions in a more competitive world
More information?
• Phil Crowcroft, ERM, Leeds
• phil.crowcroft@erm.com
• 0113 366 3240
• www.erm.com