REFERENCE DOCUMENTS - RAL25/0004 (As Published)

                    •    ERA 60 Model Operating Conditions (condition PMA003(A3)) stipulates that landfill gas must not
                         exceed the following limits:
                         -    500 parts per million (ppm v/v) at a height of 5cm above the final and intermediate cover surface
                              including the batter slopes of the landfill unit
                         -    25% of the Lower Explosive Limit (LEL) (being 1.25% v/v) when measured in facility structures
                              (but excluding facility structures used for landfill gas control and recovery, and leachate collection
                              system components)
                         -    the lower explosive limit in subsurface geology at or beyond the landfill site boundary
                         -    25% of the lower explosive limit within service pits, service trenches, stormwater drains or other
                              structures beyond the landfill site boundary.
                         -    Condition PMA005(A5) states if methane gas levels exceeding methane standards referred to in
                              condition PMA003 are detected, all necessary steps must immediately be taken to ensure
                              protection of human health.
                    •    NSW EPA 2020 bulk ground gas assessment criteria is as follows:
                         -    Sub-surface monitoring criterion (off-site migration) threshold levels for further investigation and
                              corrective action for methane is 1% (v/v) and for carbon dioxide is concentrations of 1.5% (v/v)
                              above established natural background levels
                         -    Surface emission criterion (measured 5cm above the ground surface) threshold level for further
                              investigation and corrective action for methane is 500ppm (v/v) at any point on the landfill surface
                              for intermediate and finally-capped areas
                         -    Gas accumulation criterion (enclosed structures per NSW EPA 2020 Section 5.4) threshold levels
                              for further investigation and corrective action is detection of methane at concentrations above 1%
                              (v/v)
                         -    Criteria to show that the landfill is stable and non-polluting post-closure, demonstrated in a
                              certified statement of completion (for NSW landfills per NSW EPA 2020 Section 10.2) is:
                         ○    gas concentration levels in all perimeter gas wells are less than 1% v/v methane and less than
                              1.5% v/v carbon dioxide above the established natural background for a period of 24 months.
                         ○    methane concentration at the surface of the final capping should not exceed 500 ppm.
                         -    Requirements for development on closed landfills (NSW EPA 2020 Section 10.3) includes a
                              number of requirements, including the key requirements that:
                         ○    the landfill should meet stabilisation criteria for reduction in leachate strength, stormwater
                              contamination and gas levels … the gas criteria are particularly important for developments that
                              create enclosed spaces where gas can accumulate or migrate (e.g. buildings, basements,
                              manholes, tunnels, service ducts, stormwater and sewer pipes). These criteria may be less
                              critical in the case of open developments: sporting fields, golf courses and car parks are
                              sometimes created over recently closed landfills.
                         ○    periodic methane monitoring should be conducted in all buildings and underground utilities, with
                              automatic methane sensors installed in buildings directly above landfilled areas.

                    •    NSW EPA 2016 assessment criteria is as follows:
                         -    surface emissions monitoring (NSW EPA 2016 Section 5.2) – further investigation and corrective
                              action threshold for methane monitored at 5cm above the surface is 500ppm (v/v).


        125 Lot 105 SP118458 Cooroy DSI 12062024 Rev0                                                  Lot 105 SP118458, Cooroy, QLD, 4563
        12/06/2024                                                     62                           Detailed Site Contamination Investigation
Document Set ID: 23717062
Version: 0, Version Date: 01/01/1900