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Phil Crowcroft Partner, ERM

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1 Phil Crowcroft Partner, ERM
Learning from experience – from Loscoe to Leftwich VOCs and Ground Gases Brownfield Briefing Conference November 2009 Phil Crowcroft Partner, ERM

2 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

3 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

4 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!

5 HMIP letters 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

6 Gregson Survey 2000

7 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

8 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

9 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!

10 Weston Village 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

11 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

12 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

13 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

14 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”]

15 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

16 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

17 Leftwich - Housing estate on gassing landfill (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)

18 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

19 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

20 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

21 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

22 More information? Phil Crowcroft, ERM, Leeds

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