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 phil.crowcroft@erm.com