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Who Are We?

New Methodology for Migrating Gas Protection from Landfill and Brownfield Sites to Improve Cost and Time Parameters Mark Crawford. Who Are We?. SEL Environmental Ltd have operated within the environmental sector for the last 15 years

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Who Are We?

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  1. New Methodology for Migrating Gas Protection from Landfill and Brownfield Sites to Improve Cost and Time Parameters Mark Crawford

  2. Who Are We? • SEL Environmental Ltd have operated within the environmental sector for the last 15 years • Primary expertise in Landfill gas extraction & control, landfill liners and caps • Originally a division of Site Electrical Ltd who were formed in 1981 • SEL Environmental Ltd began trading independently in 2006 • Specialists in brownfield development systems and sustainable drainage systems

  3. Who Are We? • Andy Shuttleworth, Managing Director of SEL Environmental Ltd • Qualified as a Civil Engineer in 1988 • Co-Author on the following published technical paper; Design and performance of a passive dilution gas migration barrier 2002 • Registered inventor for; GB2366504, WO0220186, US2004028475, GB2366504, GB2395103 fluid movement apparatus, trade marked as Virtual Curtain.

  4. Agenda • Legislation • Risk Management Concept • Design Considerations • Traditional Barrier Methods • Virtual Curtain System – How Does It Work • Design Methodology • Validation Trials • Case Study • Summary of Benefits • Q & A

  5. Legislation • Part II of the Environmental Protection Act (1990) • Planning Policy Statement 23: Planning and Pollution Control • Building Regulations Approved Doc Part C: Site Preparation and Resistance to Contaminants and Moisture • CIRIA C665 – Ground Gas Handbook: Assessing Risks Posed by Hazardous Ground Gases to Buildings

  6. Risk Management Concept • Source • Pathway • Receptor

  7. Typical Construction Scenario

  8. Gas regime Depth of pathway(s) Extent of pathway(s) Extent of pathway interception measures Proximity of existing and planned development Hydrogeology Existing and planned services Access Programme Design Considerations

  9. Reduce risk by removing/intercepting pathway Achieve safe construction methods (CDM) Observe good environmental practices Minimise disruption and loss of amenity Avoid damage to existing infrastructure Avoid adverse effects on site hydrogeology Eliminate/avoid odour nuisance Introduce validation/monitoring protocols Minimise maintenance requirements Cost-effective Design Aims

  10. Traditional Interception/Barrier Methods • Geomembrane • Gravel Boreholes • Gravel Trench • Geocomposites • Bentonite Slurry Wall • Active Air Barrier • Others

  11. Typical Situation

  12. The Effect of Development on Landfill Ground Gases

  13. Typical SituationUsing Traditional Methods

  14. Typical SituationDesired Method

  15. Gas Gas Gas Virtual Curtain Forced Dilution Principle • Vibro inserted vent nodes to provide preferential pathway and create low pressure curtain • Above ground inlet and outlet create differential air flow • Induces negative pressure within duct and vent nodes that attract migrating gases • Collects and dilutes gases within upper duct • Treated gases vented to atmosphere via surface components Vent bollard with 18000mm² venting area Diluted gas Diluted gas Fresh air Fresh air Forced Dilution 650mm Lightweight vented bollard base Upper duct Vent nodes Up to 10m deep

  16. Typical GeneralArrangement

  17. How Does The Virtual Curtain Work • Provides an effective “curtain” to intercept existing migration pathways. • Creates air flow through top duct using differential inlet and outlet pressures. • Disperses and dilutes gases through geocellular duct. • Controlled dilution of gases to safe levels before releasing to atmosphere through bespoke venting components. • Creates an alternative engineered preferential pathway.

  18. Installation Process Outer steel casing inserted using high frequency vibration unit

  19. Installation Process Outer casing acts as temporary shield Insert Geosynthetic Vent Node.

  20. Installation Process Remove Outer Casing

  21. Installation Process Pull node flaps through rolled out geotextile Trim Node to level and prepare geotextile

  22. Installation Process Lay geocellular duct Secure using ties

  23. Installation Process Secure combination vent terminations Place prefabricated vent bases

  24. ValidationTrial

  25. Validation Trial

  26. Validation Trial Results

  27. Case Study Scheme: Design, supply and install system to prevent carbon dioxide migration across the site boundary from adjacent landfill site. Client: Holden Homes Site: Fishwick, Preston EHO: Derek Williams Preston B.C. Date: September 2000

  28. Case Study Scheme: To effectively isolate the leisure development from the potential migration of gas from the proposed car park area all of which was constructed on landfill. Client: Kier Southern Site: Port Solent. EHO: Portsmouth City Council Date: 2000

  29. Case Study Scheme: Intercept migration pathways to prevent gas migration into the housing development. Approx 350m long curtain combination bollards at 5m centres. Client: Taylor Wimpey Site: Welwyn Garden City EHO: Hatfield B.C. Date: 2005

  30. Case Study Scheme: To eliminate the off site migration of gases due to capping a closed landfill site. “Pressure cooker effect”. This scheme uses interlocking insertion tools to effectively produce a continuous gas curtain. Client: SITA Site: Tullos Hill, Aberdeen EHO: Aberdeen City Council Date: July 2009

  31. Case Study Scheme: To provide an engineered preferential pathway for the controlled dilution to safe levels of ground gases beneath a new park and ride facility. Client: Highways Agency Skanska Site: Scarborough Integrated Transport Scheme, A64 Park and Ride. EHO: North Yorkshire County Council. Date: June 2008

  32. Case Study Scheme: Virtual curtain required to prevent potential gas migration during the capping of an old landfill. A good example to show horizontal alignment versatility. Client: North Lanarkshire Council. George Lesley Contractors. Site: Brownsburn Regeneration Park, South Airdrie. EHO: North Lanarkshire Council. Date: June – September 2008

  33. Case Study Scheme: Virtual Curtain installation to protect existing houses beyond the perimeter of a new school from potential migrating gases emanating during the filling operations during earthworks phase. Commonly known as “squeezing”. Client: Tameside, Carillion Site: Tameside BSF. Ashton Campus. EHO: Tameside Metropolitan Borough Council. Date: June 2009

  34. BenefitsEngineering & Environmental • No-dig solution, minimal generation of excavated material. • Contaminated ground remains in place. • Reduces demand for aggregate. • Reduces burden of site traffic on existing roads. • No dewatering requirements • No impact on site hydrogeology. • No impact on existing foundations

  35. Benefits – Health & Safety / CDM • Minimise exposure to contamination. • Gas dispersal is controlled and diluted. • Reduced risk from vehicle movements. • Shallow excavations.

  36. Benefits – Commercial • Low mobilisation / start-up costs • Typical installation (up to) 50m day. • Eliminate disposal of contaminated material • Eliminate importation of materials • Low maintenance requirements

  37. Benefits – Commercial Extract from recent options analysis for project in NW England 530m long x 10m deep cut-off trench: Table 5 Budget costs

  38. Traditional System vs Virtual Curtain System Which method would he choose? But it’s not up to him; it is up to you!

  39. How to stay in touch • Telephone (To be Advised) • Email: office@virtual-curtain.com • Web: www.virtual-curtain.com

  40. Thank you Any Questions?

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