Delivering sustainable solutions in a more competitive world Learning from experience – from Loscoe to Leftwich VOCs and Ground Gases Brownfield Briefing

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


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


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


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!


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


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


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


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


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!


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


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


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


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


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”]


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


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


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)


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


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


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


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


More information?

• Phil Crowcroft, ERM, Leeds

• [email protected]

• 0113 366 3240

• www.erm.com

Documents

Delivering sustainable solutions in a more competitive world Learning from experience – from Loscoe to Leftwich VOCs and Ground Gases Brownfield Briefing