Gas barrier Possible hotspot Proposed relocation of Ysgol John Bright, Llandudno, Conwy Peer review on behalf of Active ventilation Passive gas North Wales Health Authority ventilation with Passive gas of risk assessment dynamic compaction ventilation Passive gas and remediation proposal reports ventilation Dr Paul Nathanail Passive gas ventilation MA MSc PhD DIC CGeol SILC Land Quality Management Ltd at the University of Nottingham Remediation Plan General Arrangement NB Coloured polygons added for BGE/051224/ Figure 1 clarity during presentation Opening remarks Strucure of presentation • I believe that the exercise of public consultation, • Introduction (CPN & LQM) such as the meeting on 5 February 2003, should • Our brief have been carried out some time ago. • UK Contaminated Land Policy & guidance • The approach taken in investigating and • Former Gas works site remediating the sites represents commonly applied technologies. • Council Depot • The use of barriers to prevent contact with • Landfill contaminants is used in many residential and • Conclusions commercial redevelopments Paul Nathanail Land Quality Management • Specialist in Land Condition • Co author of: • Chartered Geologist – SNIFFER method • Head of Land Quality – Update to SNIFFER • University research group and private consultancy Management Group – Scottish Executive Technical company specialising in contaminated land Guidance • Director and co-owner of Land – CIRIA reports on biological and • Based at University of Nottingham Quality Management Ltd non biological methods of • Research interests: assessment and remediation • 8 technical staff – all with MSc and/or PhD – Site characterisation – Contaminated Land Ready • Clients: Reference Guide – Risk assessment – Env Agency report on wider – Local & central government, regulators, problem – Remediation strategy selection environmental value of – Sustainable brownfield holders, developers & other consultants remediation regeneration – But mainly work for Local Authorities peer reviewing • Father – Public communication & reports through planning and Part IIA involvement – Peter, age 6 – Alexander, age 2 1
Extract from our commission Scope of works The Welsh Assembly, who are providing PFI finance, have • Review risk assessment report to assess whether: requested the County to provide an assurance that "the a. the correct pollutant linkages have been identified and necessary independent technical expertise will be applied to the conceptual model of the site is robust; setting and delivering the appropriate standard for b. the assessment criteria are authoritative, scientifically remediation of the site" in response to local concerns. based and relevant (the tests in Part IIA for guideline values) In order to progress this, the Health Authority Director of Public Health has reached an agreement with the CEO of • Review Remediation Proposal report - to assess whether Conwy County for the Authority to procure an independent the proposed remediation will demonstrably break the review of the proposals. identified pollutant linkages While the Director of Public Health would commission and • Prepare letter report on the above receive the report, the intention is that the report would then • Present findings to local liaison group/ public meeting. be made available to all interested parties including the local community. All fees would be met by Conwy County. A pollutant linkage Conceptual model Contamination that could cause harm a "picture" of the site showing where the sources, pathways and receptors are in relation to one another and what significant gaps How the contaminants can travel to and be taken up by the school children in understanding remain to be plugged by further site investigation In this case the schoolchildren Contaminated land UK Policy on land contamination management in the UK • Risk based • Part IIA, Environmental Protection Act 1990 (inserted by • Suitable for use s57 of Environment Act 1995) http://www. hmso .gov.uk /acts/acts1995/Ukpga_19950025_en_5.htm#mdiv57 • Source-pathway-receptor pollutant linkage • DETR Circular 2/2000 framework http://www.defra.gov.uk/environment/landliability/circ2-2000/index.htm • Aim is to ensure no unacceptable risk given • Planning Policy Guidance Note 23 the current or intended land use • Development on Land Affected by Contamination Consultation Paper on Draft Planning Technical Advice http://www.planning.odpm.gov.uk/consult/contamin/index.htm • Cf DETR Circular 2/2000 2
Key technical guidance ICRCL 59/83 1987 http://www.defra.gov.uk/environment/landliability/pubs.htm#new • Long term basis for many contaminated • CLR 7 – gives general overview of land assessments technical guidance and legislation • Methodology essentially sound • CLR 9 – basis for selecting health criteria • Numerical trigger values were realistic but values not scientifically derived • CLR 10 – algorithms and default data for • Withdrawn on 20 Dec 2002 human health risk assessment • Other ICRCL documents have NOT been withdrawn Contaminants associated with Contaminated land issues at former gas works landfill sites • Heavy metals: Cd, Cr, Cu, Pb, Hg, V, Zn, • Landfill gas generation • Semi metals/ non metals: As, S 0 • Leachate generation • Cyanide: Complex, free/ liberatable • Complex mixture of waste potentially containing wide variety of contaminants • Others: SO 4 2- , S 2- , asbestos, pH • Organics: Phenol, aromatics, PAH, Remediation Proposed school location • Should demonstrably break all source- pathway-receptor pollutant linkages • Options adopted for Ysgol John Bright: – remove source (excavated & off site disposal) – Interrupt pathway (hard standing, passive & active venting & in ground gas barrier) 3
Komex Environmental The Secondsite (LPG) parcel Assessment SI Report to LPH 50067-7 July 2001 • Covers desk study & intrusive investigations • Made ground and gasworks structures over • Contains assessment criteria, qualitative risk alluvial/ estuarine deposits assessment and proposed remediation • Shallow perched groundwater over non • Overall a detailed competent report that identifies the aquifer; general GW flow to the east key issues expected on a site of this type • Will: • General levels of contamination were low with local hotspots (free cyanide & PAH) associated with specific – Contain part of school building, predominantly structures and post decommissioning waste disposal hard surface car park/ footpaths & some • Water levels in & out tanks differs showing they did landscaping not leak / leaked very slowly 50067-7 July 2001 Komex Report Comments Assessment criteria (Table G) • Poorly justified and now out of date • Poor QA – missing & ‘pp’ signatures – ICRCL 18/79 1986 cited in references • Site investigation rationale poorly explained – ICRCL 59/83 withdrawn Dec 2002 but considered out of date for some time • No conceptual model as such but the – No UK guidelines exist even today for many of these information on sources & pathways is there, substances poor focus on future site users, greater – No use of risk assessment models to calculate site specific parameters (cf Council Land report) emphasis given to nearby residents. • On inspection : PAH, easily liberatable cyanide & TEX seem high 50067-7 July 2001 50067-7 July 2001 The Council owned parcel of Remediation proposals land - Council Depot, Cwm Road • Formerly part of gas works and an asphalt works • Excavation and off site disposal is most common remediation technique in UK • Thin Made Ground in a depression over Alluvium • Locally elevated total PAH and TPH associated • Use of caps to break pathway is probably with Garage & Gas Holder A second most common • Will: • Extent of remediation areas poorly justified – Contain part of school building, soft landscaping & car • No proposed removal of gas holder contents parking 50067-7 July 2001 50067-8 July 2001 4
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