Presentation on theme: "Phil Crowcroft Partner, ERM"— Presentation transcript:
1 Phil Crowcroft Partner, ERM Learning from experience – from Loscoe to Leftwich VOCs and Ground Gases Brownfield Briefing Conference November 2009Phil Crowcroft Partner, ERM
2 Abbeystead 1984Natural methane released into water supply tunnel from deep limestone geologyPushed into valve house by start of water pumpingIgnition source not known, but visiting group from local community present16 killed by explosionVent stale air to atmosphere, not building
3 Loscoe 1986 Inert waste landfill surrounded by housing Later amendments to licence allowed domestic waste to be tippedEvidence of vegetation dieback in surrounding lawnsLFG migration through bedrock driven by rapid fall in atmospheric pressure (29mb in 7 hours)Gas entered bungalow, ignited by boiler switchTwo injuredHouses 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 propertiesCost of gas protection measures highBritish Coal proposed to move villageNew community built nearby, old housing demolishedShallow part-worked seams then opencasted to provide revenue to cover cost of building new communityThink big!
5 HMIP lettersChief 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 developmentFollow-up letter in 1989Boom in soil probing and borehole investigationsNumerous sites identified where housing built on or close to landfill75% of Dudley within 250m of landfill
7 Westleigh, Lancashire 1988Housing development under construction next to deep domestic waste landfillBoulder Clay overlying Coal MeasuresMine shaft in housing areaGas seen bubbling up through puddles in garden areas of part built housesBuilding stopped, litigation followedFinal solution involved sealing sides of landfill, deep vent trenches, sealing of mineshaftFinished 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 hourEnhance gas abstraction at landfillRemove floor and install venting zone and membrane in housePositive pressurisationGas detectionRemote dial-out and control - don’t under-estimate speed of gas movementSubstantial 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 heaveClayboard used, comprising corrugated cardboard, which collapses when wetAlso produced methane, and this ignited when hole drilled through slab, flash over singed hairCricket ground stand – same construction, feared same problemSlab drilled, and methane found at high concentrationsClayboard tunnelled outBeware or unexpected consequences of building products!
10 Weston VillageICI disposal of hexachlorobutadiene (HCBD) in landfill in sandstone quarries in 1950/60sTesting found low concentrations in boreholes and properties near quarriesProperties zoned by risk, green, blue and unzonedWhole 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 villageOffer created unexpected side effectsCompensation 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 townLocal services deteriorated as people left, despite ICI stated intent to keep village togetherBut 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 benefitCommunity-based chemical contamination is always a social issueHealth effects as much from worry, uncertainty and upheaval, as from actual contaminationBiggest mistake? Allowing whole village to become associated with, and stigmatised by incident
13 School site 2007Part 2A investigation showed primary school partly over old gassing landfillInternal air monitoring showed naphthalene above backgroundVarious other VOCs present attributable to paint, cleaning fluids etcConcerns includedhistory of various cancers amongst staffpresence of mobile phone mast next to schoolpotential for blight of school if problem publicised
14 Brewery site, London 2008 - naphthalene Odours detected in occupied refurbished apartments in former Brewery buildingNaphthalene measured at significant concentrations, Part 2A DeterminationSource found to be impregnated timbers encased in concrete basement floorTimbers removed, remedial targets were to show no residual riskChallenge was to prove that gas reduced to below backgroundMeasurement 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 homeHealth and safety issues for existing subfloor void entryFluctuating groundwater entering void at times of heavy rainVOC 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 slabPositive pressure air system installedFloating membrane laid in base of voidInsulation of floor slab above voidEquitable 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 groundInvestigation revealed relatively high concentration, low flow rate methane locallyTemporary gas detectors installed in houses whilst works progressedTracer 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 voidsreplacement 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 wallsremoval of all waste to depth of 4 metres in gardens of six worst affected propertiesreplacement with inert fill and reinstate gardenslarge 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 onework with the community directly affected (24 houses)allow them to be part of the decision-making bodyprovide a consultant that reports to themensure 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 riskHealth risks from VOCs are only slowly becoming understoodSociety is moving towards a low tolerance of residual riskSocial impacts will often over-ride all other concerns unless there is death or injury
22 More information? Phil Crowcroft, ERM, Leeds firstname.lastname@example.org
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