generation rates of landfill gas (> 250 m3/hr), whereas
passive systems are used for smaller rates of landfill gas (< 250 m3/hr) generation.
As landfill gas contains water vapour, both active and passive landfill gas management systems require
adequate condensate (contaminated water) collection and drainage points to prevent this water blocking and/or damaging the installed system.
Landfill gas extraction wells are a critical element of a landfill gas management system. There are two kinds of extraction wells; vertical and horizontal. A site’s landfill gas management system should include one or both of these types of wells as required.
Active and passive landfill gas extraction wells are the same design and can be used interchangeably between both systems. Horizontal gas wells are used during landfilling operations and may be superseded by vertical gas wells once an area has been completely filled and intermediate and final cover materials have been placed. Vertical wells should extend to within 3 to 5 metres of the base of the waste mass.
The design and location of the gas management infrastructure should minimise damage by settlement, vandals, animals, natural processes or operational machinery. Landfill gas extraction wells should be monitored and maintained or replaced as required. An appropriate level of construction quality assurance (CQA) must be completed during the installation of a landfill gas management system. Any variations from the design made during the construction phase should be recorded and held by the landfill site owner/operator.
6.7.2 Air toxics
Assessment of air toxics should be undertaken as part of the landfill gas risk assessment (LFGRA). Landfill gases can contain a range of air toxics, depending on the type of waste that has been deposited.
Consistent with world best-practice and to ensure protection of public health, a monitoring plan should be developed and implemented for air toxics, where required. Advice should be sought from an environmental auditor during the development or review of the LFGRA. The monitoring should include the bores and ambient air at the boundary of the site. The air sample should be analysed for the indicators specified in the SEPP (AQM) that are relevant for landfill gases or those contained in international guidance on monitoring of air toxics from landfills.
BPEM requirements to comply with clause 15 (3) and (4) of the Landfill WMP
LANDFILL GAS
Relevant BPEM objective
Ensure that no safety or environmental impacts are caused by landfill gas.
Required outcomes of the BPEM
• Undertake a site-specific landfill gas risk assessment. • All practicable measures must be taken to achieve the
landfill gas action levels detailed in Table 6.4. • Develop and implement an appropriate landfill gas
management system.
• Implement a landfill gas monitoring program in accordance with the Landfill licensing guidelines, EPA publication 1323.
• lmplement a landfill gas remediation action plan acceptable to EPA if the action Levels in Table 6.4 are exceeded.
• The landfill gas management system is updated and is in compliance with the landfill gas management hierarchy. • Notify EPA Victoria within 24 hours of detection of any
exceedance of the action levels detailed in Table 6.4, except for onsite exceedance rectified within 24 hours. • The landfill gas flares must have auto ignition and flame
arrestor beneath the combustion zone.
Suggested measures of the BPEM
• Include landfill gas management systems in the landfill design.
• Install the landfill gas management system progressively during the landfilling process, to minimise uncontrolled landfill gas emissions.
• Where there are multiple landfill sites in relative proximity, examine the options for higher order measures of landfill gas utilisation of the combined landfill gas produced from the sites.
6.7.3 Odour
Landfill odour is a key consideration in landfill siting. Landfill odours have two main sources; odour from the aerobic decomposition of freshly deposited wastes and odour from landfill gas generated by the anaerobic decomposition of wastes. Leachate ponds can also be a source of offensive odours. Good operation and adequate buffers are essential in odour management. These buffers are set to account for upset conditions and are not a substitute for best-practice management at the landfill or for normal operating conditions.
At all times, a landfill must be managed to prevent offensive odours beyond the boundary of the premises. For existing landfills this will be assessed by community complaints that are verified by EPA officers. In particular, where surrounding land uses include residential,
Siting, design, operation and rehabilitation of landfills
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highest degree of care must be taken to protect these areas from landfill odours.
The provision of buffers in accordance with requirements outlined in section 5.1.5 will minimise impacts of odour on surrounding areas.
While the major constituents of landfill gas, methane and carbon dioxide, are odourless, other minor constituents of landfill gases including organosulfur compounds can be very odorous. The key means of managing landfill gas odour is to manage the landfill gas in general by oxidising it through some of the measures discussed in section 6.7.1. Odour from aerobic waste deposition is managed by minimising the exposure of these wastes to the atmosphere.
6.7.4 Dust emissions
Any large area where the land has been disturbed and is subject to vehicular traffic has the capacity to generate dust. Other potential dust sources are stockpiles of earth and the delivery of dusty loads of waste.
The magnitude of the impact will depend on the: • type and size of the operation
• prevailing wind speed and direction • adjacent land use
• occurrence of natural and/or constructed wind breaks • wind-abatement measures or buffers.
Dust can impact on both health and amenity, depending on the size of the particles. Reactive management strategies should put in place including real-time
monitoring of PM10. The monitoring may be required at the
boundary of the premises both upwind and downwind of the active landfill area to assess any impact and guide mitigation actions.
An hourly trigger level of 80 µg/m3 should be used to
assess the real-time data. If exceeded additional dust management practices, such as increased water sprays and dust suppressants should be applied.
Dust suppression measures to be applied at the site include:
• vegetating or mulching of exposed areas and formation of internal roads, including sealing roads that are used regularly
• use of water or other dust suppressants on roads or stockpiles that are not sealed or vegetated
• where leachate is to be used for dust suppression it may only be applied to areas that are within the active landfill cell to ensure the leachate does not
contaminate stormwater run-off.
BPEM requirements to comply with clause 15 (3) and (4) of the Landfill WMP
ODOUR, DUST AND AIR TOXICS
Relevant BPEM objective
To ensure that air quality objectives are met, and that there is no loss of amenity from odour or dust.
Required outcomes of the BPEM
• Prevention of any offensive odours beyond the boundary of the premises.
• Control all dust emissions from the landfill site.
Suggested measures of the BPEM
• Vegetate exposed areas and form internal roads. • Ensure waste is covered appropriately and on time. • Implement a reactive management plan including real-
time monitoring for PM10, where necessary.
• Monitoring of air toxics should be undertaken where required.
6.8 Bioreactor landfills
Bioreactor landfills are landfills that seek to maximise the rate of degradation of biodegradable wastes.
Generally, waste degradation in a conventional ‘dry tomb’ landfill is inhibited by the lack of moisture within the waste which impedes the rate of waste decomposition. The addition of moisture in a bioreactor landfill by way of leachate recirculation or fresh water infiltration adds moisture to the waste and promotes the conditions necessary for micro-organisms to achieve rapid rates of waste decomposition.
Bioreactor landfills seek to complete the biodegradation of the readily and moderately degradable wastes within five to 10 years of waste placement.
The enhanced degradation of waste process can be undertaken under both anaerobic and aerobic conditions. In both cases, moisture content of the waste is the most important factor in promoting decomposition of waste. These guidelines mainly refer to anaerobic bioreactor landfills due to the beneficial use of generated methane gas while decreasing greenhouse gas emissions. Aerobic or semi-aerobic bioreactor landfills are likely to pose an unacceptable fire risk and are not recommended. The environmental performance and required outcomes for a bioreactor landfill are the same as for a conventional landfill (refer to ‘Required outcomes’ in Section 8.1).