Understanding Gas Protection Measure Selection within ...

1 Understanding Gas Protection Measure Selection within Waterproofing SystemsJohn Naylor Technical DirectorThe Main Hazardous Gases CH4CO2H2 SRnN2 COVOCsH2 Sources of UK ground-gas Natural Bedrock and sediments containing Uranium Calcareous rock (limestone) Coal bearing strata Organic sediments (peat, alluvium) Anthropogenic Landfill Made ground Mining Past contaminative activityPBritish CoalfieldsRisks from: Methane Carbon Dioxide Carbon Monoxide Hydrogen Sulphide Oxygen deficiencyAbbeystead Valve House Disaster, 1984 16 people killed28 people injured June 2014 Carbon dioxide discovered in Gorebridgehomes2017 Update64 homes demolished23,000 former landfills in England & WalesLoscoeExplosion, 19863 people injured Radon GasSource: HPA-RPD-033 Indicative Atlas of Radon in England and Wales 2007 INDICATIVE Radon is the second highest cause of lung cancer in the UK, after smoking Average Annual Radiation DosePublished June 2015 Increased scope (site investigation and risk assessment) Updated to latest good practice Includes changes to building types Expanded and modified scoring tables VerificationBS 8485:2015 Ground-Gas Risk Assessments Tier 1 -Is there a pollutant linkage?

2 -Initial Conceptual Site ModelTier 2 -Generic risk assessment -What is the empirical level of risk? -Need sufficient monitoring data to determine a GSV and a Characteristic SituationTier 3 -Site specific risk assessment-What is the quantitative risk?-Use numerical models to calculate gas accumulation beneath & within buildings-Detailed qualitative risk assessmentTier 4 -Receptor monitoring-Monitoring directly at or near to the receptorWhich ever tier use multiple-lines of evidence Conceptual Site Model DevelopmentUsing site investigation data and monitoring data to identify plausible pollution linkages that require further management 010203040506008 Jul10 Jul12 Jul14 Jul16 Jul18 Jul20 Jul22 Jul24 Jul26 Jul28 Jul30 JulWeekly monitoring on these dates shows almost no methaneWeekly monitoring on these dates shows falling methaneWeekly monitoring on these dates shows rising methaneMethaneGround Gas VariabilityConcentration (%v/v)BS8485.

3 2015 Characteristic SituationsCS1 Very LowRiskNo Specialprecautions requiredCS2 LowRiskPassive Gas Protection (<30m span)CS3 ModerateRiskHighest level of passive Protection and limit for private unmanaged residential dwellingsCS4 Moderate to High RiskLoweractive systems for commercial and industrial. Managed residential possible with RiskLarge industrialsheds with large open areas. Really think about RiskYes even here you can develop, but should yoube building on it?BS8485:2015 -Building Types & SensitivitySource: Table 3 from BS8485:2015 Requires Professional Judgement Can have different types in the same buildingBS8485:2015 -Scoring Determine your minimum score requirements using a combination of twoormore of the following elements: Ventilation measures Structural barrier or basement Gas-resistant membraneYou can t use the same element twice!

4 There are several additional notes to this table You may consider different parts of the building requiring different scoresBS8485:2015 -Gas Protection Score, Table 4BS8485:2015 -Table 5 Structural Barrier Not all concrete is the same! Any breaches in slabs need sealing Annex A provides further detailBS8102:2009 Type or Grade?Gradeis the end use1 Car parking2 Plant rooms and workshops3 Ventilated residential and commercial areasTypeis the Protection systemA -BarrierB Structurally integralC Drained BS8485:2015 -Ventilation Much more detail in this version Need to design it Proveyour ventilation works No active for Type A BuildingElementScorePressure sub floor ventilationVery Good dispersal to to car park(to approved Doc F)4 Gas resistant membranes meeting ALLof the above requirements HERO or ZEROBS8485:2015 -Table 7 Detail in Design, Detailing in InstallationCIRIA C735 -Verification All installations should have some form of verification Verification should be proportionate to.

5 A) the risks from the site, B) the experience of the installation operatives Verification should be conducted by suitably qualified and Independentpractitioners. The process of demonstrating that the risk has been reduced to meet remediation criteria and objectives based on a quantitative assessment of remediation performance C735 Decision StructureCIRIA C735 Figure Verification Plan Verification Plan s should include: Site summary Design / specification compliance Acceptable installation methods Installer / verifier competencies Inspection / testing regime Non-conformance resolution Define Contents of Final Verification ReportIntegrity Testing a) In line with methodologies in Annex 2, 3 and 4 of CIRIA 735 (Leak Detection) Smoke Testing Tracer Gas Testing Dielectric Testingb) In line with methodologies in ASTM D4437 (Seam Testing)

6 Pick/Probe Test Air Lancing Pressure TestingThere are also othersVerification MonitoringPre and Post Remediation Monitoring EvidenceSummary1 Site Investigation desk study trail pits monitoring laboratory analysisWeeks to Months2 Risk Assessment Conceptual Site Model Consideration of gases and vapours Generic GSV Detailed assessment Assigning Characteristic Situation3 Design & Specification Proportionate to the risks posed BS8485 points Scoring System Ventilation Structure MembraneBS8102 Considerations4 Installation NVQ Level 2 Qualification Protection from Follow on Trades5 Verification C735 Verification Plan Independent Integrity testingThank you 244 224 or 0161 232 general enquiries.