TESTING AND VERIFICATION OF GAS PROTECTION SYSTEMS [CIRIA C735]

Transcription

1 TESTING AND VERIFICATION OF GAS PROTECTION SYSTEMS [CIRIA C735] July 2015

2 . OUTLINE OF PRESENTATION Guidance on membranes as VOC barriers [CIRIA C748] Testing and verification of gas protection systems [CIRIA C735] 1. The Project 2. Project Issues 3. Verification Procedure 4. Integrity testing 5. Reporting 6. Recommendations Case study Conclusions

3 GUIDANCE ON MEMBRANES AS VOC BARRIERS [CIRIA C748] Authors S Wilson (EPG) S Abbot (TCNF/ University of Leeds) S Mallett (Buro Happold) Background 1. Gas membrane break VOC migration pathways 2. VOCs migrate through polymeric materials 3. Guidance presents information on permeation 4. Risk based approach

4 GUIDANCE ON MEMBRANES AS VOC BARRIERS [CIRIA C748] Membrane function Hydrocarbon resistant HDPE not impermeable to VOCs Vapour transport mechanisms Permeation tests Membrane performance factors

5 GUIDANCE ON MEMBRANES AS VOC BARRIERS [CIRIA C748] Membrane durability 1. Potential chemical degradation 2. Chemical resistance tests

6 GUIDANCE ON MEMBRANES AS VOC BARRIERS [CIRIA C748] Membrane Selection Design Life Degradation Risk associated with VOC migration Potential for exposure Loading Installation Installation and verification

7 TESTING AND VERIFICATION OF GAS PROTECTION SYSTEMS [CIRIA C735] October 2014

8 C735 PRESENTATION STRUCTURE 1. The Project 2. Project Issues 3. Verification Procedure 4. Integrity testing 5. Reporting 6. Recommendations

9 C THE PROJECT Need Installed gas protection systems often inadequate Verification - fundamental to remediation Little current guidance for verification of gas protection systems Verification absent in design/ construction of buildings with gas protection systems Membrane resilience and integrity and well designed venting systems fundamental to performance of gas protection systems

10 1. THE PROJECT Need

11 1. THE PROJECT Need

12 1. THE PROJECT Need

13 1. THE PROJECT Team CIRIA PSG Chair Research Contractor PSG - J Kwan - G Card (GB Card) - L Cox neetaffel -Andureau (Buro Happold/Arup) - M Corban (MEC Environmental) - H Mallett (Buro Happold) - S Wilson (EPG) - 27 members from: NHBC LA & EA regulators contractors consultant suppliers

14 1. THE PROJECT Objectives 1. Determine and promote good practice 2. Define need and scope of verification 3. Describe integrity test methods and their selection 4. Identify practical constraints 5. Set out details of Verification Report [ CLR11 and SC030114]

15 1. THE PROJECT Regulatory framework Part 2A [Statutory guidance] Any remedial treatment action should include appropriate verification measures. In arranging for such measures, the enforcing authority should ensure that the person responsible for verification is a suitably qualified experienced practitioner. (Defra, 2012) NPPF Responsibility rests with developer Competent person CLG 2008 [Standard Conditions] Following completion of measures identified in the approved remediation scheme, a verification report (referred to in PPS23 as a validation report) that demonstrates the effectiveness of the remediation carried out must be produced, and is subject to the approval in writing of the Local Planning Authority.

16 1. THE PROJECT Regulatory framework NHBC [Chapter 4.1] Robust design and verification required [Cl D6 and D7] Specialist membrane installers [CSC National Occupational Standards VR612,613; NVQ level 2 Diploma Installation of gas membranes] Suitable person to prepare Verification Reports [Appendix 4.1D] Verification required on higher risk sites (Amber 2 and above) CIRIA [C735] The role and responsibilities of the local authority as primary regulator of land contamination, including land affected by ground gas emissions, is important for their assessment and approval of both the developers initial planning proposals (including remedial strategy) and the post development verification report

17 2. PROJECT ISSUES 1. Verification 2. Ventilation 3. Membrane integrity 4. Robustness and levels of redundancy 5. Conceptual Site Model

18 2. PROJECT ISSUES 1. Verification currently insufficient attention in design of gas protection systems A Verification Plan should be prepared as an integral part of the gas protection system at the design stage and submitted to the local authority regulator as an integral part of the remediation strategy. The verification plan should address i. Gas regime and gas protection system ii. Inspection regime iii. Integrity test programme (if any)

19 2. PROJECT ISSUES 2. High permeability layer and venting. 1990s reports - efficacy of venting Wilson & Card - proven screening method CIRIA C735 - high level of redundancy Ventilation is a very effective first line of defence in gas protection systems.

20 2. PROJECT ISSUES 3. Integrity of membranes BRE Minimum 1200g polyethylene Intact survival during construction. CIRIA C735 Critical property ability to survive construction intact. Key parameters material type; tensile strength, puncture resistance; permeability; need for protection; thickness (if welded).

21 2. PROJECT ISSUES 4. Robustness and levels of redundancy Increase with Characteristics Situation [Basis of approach in Wilson&Card 99, CIRIA C665, British Standard 8485, NHBC 2007]. 5. Conceptual site model An appropriate understanding of the conceptual site model is a critical element in the verification process

22 3. VERIFICATION PROCEDURES Need for appropriately qualified workforce Verification by competent experienced trained personnel. Third party verification Risk based approach to verification activities. Verifying that a gas protection system works is as important as design and installation. A Verification Plan should be prepared as an integral part of the gas protection system at the design stage and submitted to the local authority regulator as an integral part of the remediation strategy.

23 3. VERIFICATION PROCEDURES Risk based approach to verification and independence Requirement for 3rd party verification increases with risk. Environment Agency recommends avoidance of conflicts of interest in verification [independent verifier]

24 3. VERIFICATION PROCEDURES Inspection Verifier (independent or not) to be; Competent Experienced Suitably trained Pro Forma

25 3. VERIFICATION PROCEDURES Competence of installer Appropriately experienced & qualified workforce install gas protection system If not more intensive verification required Relevant qualification CSC level 2 NVQ Diploma in sub structure work occupations (Construction) installation of gas membranes. Qualification helps ensure work complies with National Occupational Standards V612, V613. A qualified workforce helps ensure adequate gas membrane installation and can make provision for less onerous verification plans.

26 4. INTEGRITY TESTING Combine with visual inspection Risk based Not Substitute for well designed/ installed gas protection systems Not to be used to obtain BS 8485 points

27 4. INTEGRITY TESTING a) Seams - Air channel - Mechanical - Air lance b) Areal - Tracer gas - Smoke - Dielectric porosity All have advantage and limitations. Risk based decision on need Planned Practical application/ limitation.

28 4. INTEGRITY TESTING - METHODS Standard specifications for 1. Tracer gas test 2. Smoke test 3. Dielectric porosity test

29 4. INTEGRITY TESTING - METHODS Integrity testing Issues to consider 1. Definition of test method 2. Issues specific to test type

30 4. INTEGRITY TESTING Selection of verification & integrity testing Annex 1 Risk based structure for verification and integrity testing Considers; Development type Gas regime Slab type Installer experience Provides Level of verification Type of integrity testing Read the explanatory Notes

31 5. REPORTING Accord with CLR11, SC030114/RI and NHBC Chapter 4.1, Tech Extra 07 Clear concise description of verification activities Phasing Verification report - Contents list Lines of evidence - Description of inspection regime - Description of elements of gas protection system - Presentation of material specifications etc. Meet regulatory requirements (inc planning conditions)

32 6. RECOMMENDATIONS 1. Recognition of CLO role and responsibility 2. Use of Conditions to require verification 3. Reject unsuitable reports 4. Upskill workforce [CSC - competent person] 5. Installers have / working towards NVQ 6. Verification plan integral element of strategy

33 6. RECOMMENDATIONS 7. Recognition of independent verification as important element 8. Risk based decision on verification (independence, gas regime, gas protection system, quality of product, installer competence) 9. Verifier independent, competent, experienced 10. Proprietary gas membrane should be specified [material type, tensile strength, puncture resistance, permeability, thickness (welded) & protected] 11. Research into integrity test methods 12. Use of standard inspection pro formas

34 CASE STUDY Question for you What is this a picture of?

35 CASE STUDY New building with passive gas protection measures Void former Membrane Venting via perimeter granular filled trench Verification

36 CASE STUDY Drawings prepared by Engineer Contractor installed gas protection system

37 CASE STUDY Drawings prepared by Engineer

38 CASE STUDY Contractor installed gas protection system

39 CASE STUDY 1. Membrane sealed over vent pipes 2. Concrete pavement laid 3. Debacle! But solved by good verification 1. Inspection 2. Identify issue 3. Devise solution [in conjunction with specialist & contractor] 4. Implement and 5. Verify and record

40 CONCLUSIONS 1. Installed gas protection systems often inadequate Solution: Adopt C Verification plan integral to Remedial Strategy 3. Ventilation VIP of system 4. Maintenance of membrane integrity 5. Integrity tests planned implemented by competent persons [as required] 6. Upskilling of workforce and verifier 7. Risk based approach to verification [activities, type, frequency, competence]

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