REFERENCE DOCUMENTS - RAL25/0004 (As Published)

        6.5.        VAPOUR AND LANDFILL GAS SAMPLING
                    The disposal of night soil over the AEC 1 northern portion of the site is associated with the likely historical
                    generation of landfill gas (LFG or biogas). There was no historical or field evidence of landfilled
                    putrescible materials over the AEC 2 southern portion of the site.
                    Whilst decomposition over the subsequent approximately 50 years since deposition is expected to have
                    limited present-day LFG generation, confirmatory evidence was required in accordance with:

                    •    NSW EPA Contaminated Land Guidelines - Assessment and management of hazardous ground
                         gases, 2020 (NSW EPA 2020)
                    •    DES (now DESI), 2017, Model operating conditions, ERA 60 – Waste disposal. Brisbane: Department
                         of Environment and Science Government (ERA 60)
                    As with general land contamination assessment, and as noted by Section 3 of NSW EPA 2020, a staged
                    approach was undertaken to maximise the effectiveness of the LFG site assessment work and minimise
                    its costs, with opportunistic surface monitoring undertaken during DSI 1 and a formal sub-surface
                    assessment during DSI 2.

        6.5.1.      DSI 1 LFG WORKS
                    The technique of surface emission measurement may be applied to bulk gases of typically closed landfills
                    or other filled ground (NSW EPA 2020, Appendix A4.1, Table 18). Opportunistic surface monitoring during
                    DSI 1 was used to provide an additional line of evidence to confirm the CSM and support future LFG
                    borehole placement, with all test pits screened, including those over AEC 2 where an LFG source was not
                    expected.
                    With an absence of major service trenches or similar underground infrastructure, the surface screening
                    focused on the excavated test pits, any adjacent cracked soil voids, site boundary adjacent housing and
                    the recently constructed shed.
                    With reference to Section 3.4.4 and Appendix A4.5.2 of NSW EPA 2020 and Section 5.2 of NSW EPA
                    Environmental Guidelines, Solid waste landfills, 2nd edition, 2016 (NSW EPA 2016) the DSI 1 surface
                    monitoring methodology included:

                    •    Using a calibrated “Eagle 2” landfill gas monitor with a methane senor detection level of at least
                         20ppm, with the monitor able to further record at explosivity (PID surrogate), carbon dioxide and
                         oxygen (refer to Appendix O for calibration certificate)

                    •    Testing undertaken preferably during low wind conditions (<10km/h) and relatively low and stable
                         atmospheric pressure (less than 101.3 kPa)

                    •    The LFG monitoring occurred as follows in accordance with the SAQP:
                         -    in the atmosphere no greater than 5cm above the ground surface or otherwise within the
                              excavated test pit at various recorded depths within 5cm of the test pit base or wall
                         -    continuous transects at the site boundary immediately bordering residential housing located east
                              and west of the site.
                         -    within and around the shed at various ground and ceiling locations.




        125 Lot 105 SP118458 Cooroy DSI 12062024 Rev0                                                  Lot 105 SP118458, Cooroy, QLD, 4563
        12/06/2024                                                   49                             Detailed Site Contamination Investigation
Document Set ID: 23717062
Version: 0, Version Date: 01/01/1900