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IRP - IGM

The Presented Case Studies. The site names are fictionalSite plans and aerial photos are not the real investigation sites, and are representative onlyThe conceptual models are representative of real sites used during the researchThe site factual data, including logs have been simplified and all references to real sites removedThe hi-frequency data has been collected from the research field studies.

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IRP - IGM

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    2. The Presented Case Studies The site names are fictional Site plans and aerial photos are not the real investigation sites, and are representative only The conceptual models are representative of real sites used during the research The site factual data, including logs have been simplified and all references to real sites removed The hi-frequency data has been collected from the research field studies

    4. Case Study 1 – The Docks Former docks. Over time the base filled with organic sludge and other waste and had not been used for several years A clay bund was created across the middle of the dock, with the organic sludge being removed and backfilled predominantly with sand to reclaim land for dock storage use This storage use was expanded with a steel sheet pile wall being put across the dock opening and filled with inert waste

    5. Case Study 1 – Aerial Photo

    6. Redevelopment Proposals Regenerate the area for a mixed commercial (shops and offices) with residential apartment use 3 Blocks spanning across the infilled dock with associated parking and landscaping Requires outline planning to secure funding Site investigations have revealed a ground gas risk

    7. Conceptual Model

    8. Spot Monitoring Spot monitoring revealed high concentrations of methane (@50%v/v), carbon dioxide (@20%v/v) and depleted oxygen and low flow on the ship canal side of the bund Occasional low concentrations of methane and slightly reduced oxygen with variable flow of the land side of the bund However, further detail required to understand the gassing regime for protection design and provide confidence that no gas was passing across the bund

    9. Spot Monitoring

    10. Spot Monitoring

    11. Hi Frequency Monitoring GasClam instruments were installed within the organic sludge and made ground and within the sand fill on the other side of the bund Elevated methane and carbon dioxide was found in the organic sludge and made ground – no surprises there! Low concentrations of methane were detected on the sand filled side of the bund, with slightly reduced oxygen levels. Interestingly negligible carbon dioxide?

    12. To The Machines! Open up file The Docks.xls Plot multi-parameter time series data graphs for both BHA and BHB Plot all bulk gases and atmospheric pressure on one graph for each borehole Plot separate graphs for differential pressure and water level for each borehole Plot the above graphs on the same worksheet for each borehole (for viewing!)

    13. Hi Frequency Monitoring

    14. Hi Frequency Monitoring

    15. Application of Hi-Frequency Data to Gas Screening Values Why not! Provides a much bigger data set GSV = gas flow rate x concentration/100 Max Gas Value or selected %ile Concentration Duration Value? Gas Flow Rates – Spot Monitoring BUT – DON’T APPLY BLINDLY !!!

    16. Max Gas or Concentration Duration? Depends on the site specific setting, amount and confidence in the data collected – have we recorded likely worst case conditions? What value do we use? Max value, 99th, 95th, …, 51st%ile

    17. To The Machines! Open up file The Docks.xls Plot concentration duration curves for both BHA and BHB Select Concentration Duration Tab Create a percentage time column Create concentration columns and sort descending Plot a graph of Percent time (x axis) by Concentration (y axis) for all bulk gases

    18. Concentration Duration Curves

    19. Gas Flow Rates Spot sampling method using a flow meter Typically negligible or very low with some short initial positive flows Consider assumptions and limitations of this monitoring Can use statistics (probability distribution function) Gas flow input values for GSV calculation are: BHA: 2.4 l/hr max (total gas) BHB: 4.5 l/hr max (total gas)

    20. To The Machines! Open up file The Docks.xls and GSV tab Work out the GSV values for the data

    21. GSV Calculation GSV= Gas Flow (ltr/hr) x Gas Concentration (%) / 100

    22. Lines of Evidence Desk Study Conceptual Model Investigation & Monitoring Design and Findings Concentration profile and duration Any other correlations? Changes over time (1 in 100 year events?) Construction Design (and future modification) Others……..environmental conditions etc Conceptual Model – yes – again!

    23. Case Study 1 Conclusions The hi-frequency monitoring provided much greater detail and confidence Lines of evidence can and should be used to strengthen the assessment and identify any weaknesses Better information available for the design team and regulator to consider – a fit for use design and faster turnaround…

    25. Case Study 2 – Kiln Lane Former clay pit and brick works Infilled with various waste types between 1930s and 1970s including ash and brick waste, textile, household and inert waste. Redeveloped for residential housing in the 1980s Identified as a Part 2A Potential Site of Concern and intrusive investigations undertaken

    26. Case Study 2 – Aerial Photo

    27. Conceptual Model

    28. Spot Monitoring Spot monitoring revealed Highly variable ground gas concentrations with variable flow rates at the site Unable to distinguish ground gas regime with confidence

    29. Spot Monitoring

    30. Spot Monitoring

    31. Spot Monitoring

    32. Hi Frequency Monitoring Gasclam instruments were installed within different types of landfill waste Variable ground gas concentrations were recorded as found with the spot sampling Correlations noted within the data Data supported the zoning of the site based on waste type and gas concentrations present

    33. To The Machines! Open up file Kiln Lane.xls Plot multi-parameter time series data graphs for BHC

    34. Hi Frequency Monitoring

    35. Hi Frequency Monitoring

    36. Hi Frequency Monitoring

    37. Correlations Look for correlations between parameters Bulk gas concentrations Atmospheric Pressures Confidence on reasonable worst case Think about the site and borehole setting

    38. To The Machines! Open up file Kiln Lane.xls Plot concentration duration curves for Borehole C Select Concentration Duration Tab for BHC Create a percentage time column Create concentration columns and sort descending Plot a graph of Percent time (x axis) by Concentration (y axis) for all bulk gases

    39. Concentration Duration Curves

    40. Concentration Duration Curves

    41. Concentration Duration Curves

    42. Gas Flow Rates Spot sampling method using a flow meter Consider assumptions and limitations of this monitoring Ground Gas Recovery Tests Indicative of ground gas flux Can be useful for understanding ground gas regime Use as a check, not as a quantity in the GSV calculation

    43. To The Machines! Open up file Kiln Lane.xls Plot ground gas recovery profiles for both BHA, BHB and BHC Plot CH4 and CO2 against time in hours

    44. Ground Gas Recovery Profiles

    45. Ground Gas Recovery Profiles

    46. Ground Gas Recovery Profiles

    47. Gas Flow Rates Spot sampling method using a flow meter BHA – limit of detection of instrument BHB – variable – typically between –2 and 4.3 ltr/hr BHC – large initial flows with steady state typically between 2 to 6 l/hr Ground Gas Recovery Tests BHA – recovery over days BHB – recovery over hours BHC – recovery within minutes

    48. To The Machines! Open up file Kiln Lane.xls and GSV tab Work out the GSV values for the data

    49. Gas Screening Values

    50. Detailed Risk Assessment Estimation of ground gas movement Pressure or Diffusion Pecksen Method (flow x conc. / 10) Darcy’s (Pressure) & Fick’s (Diffusion) laws Steve Wilson’s Modular Approach Landsim, VOLASOL, J&E, CLEA?…

    51. Lines of Evidence Just as Case Study 1 to the nth Case Study Always consider the desk study information and conceptual model Use several tools at your disposal to show the evidence points to the same conclusion Use sensitivity analysis

    52. Contact Details Urban Vision: John Naylor E: john.naylor@urbanvision.org.uk T: 0161 604 7650 Simon Talbot E: simon.talbot@mac.com T: 0788 444 4272 University of Manchester: Dr Peter Morris Project Coordinator E: peter.morris@manchester.ac.uk T: 0161 275 0183 Salamander: Dr Stephen Boult E: s.boult@salamander-group.co.uk T: 0845 053 1234

    53. THANK YOU!

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