Closed Landfills Potential Risks and Guidelines

Introduction

Landfill is an area filled with waste material composed of a complex mixture of municipal and hazardous waste, disposed of by either individual, households and/or organisations (Staines, 2004).  Hazardous waste contains a high degree of toxicity as it includes contaminated soils, refinery waste, chemical processes and other by-products of commercial and industrial processes (Staines, 2004).  Municipal Waste (MW) is comprised of various materials mainly from household and commercial use (Chu, 2008).  Once landfills sites have reached their capacity, they are closed (Chu, 2008). As the demand for usable land increases, closed landfills are often used constructively to build parks, golf courses and sportsground ( Environment Protection Authority Victoria, 2015) . This is the case in the small town of Kouldwetsoque, where a sportsground and clubhouse has been built on a former landfill rubbish tip. However, years after its construction residents are complaining of strong odours coming from the site in particular the club house.  Due to poor records, the extent of the fill is unknown, however thought to be mainly general municipal landfill tip receiving household and general waste from the local area. Closing and reusing landfill sites offers many challenges, if appropriate closure measures have not been followed or if the proper engineered containment systems have not been implemented ( Environment Protection Authority Victoria, 2015). This can cause problems such as leaching hazardous substances, pungent odours and gas leaks, which can occur up to 30 years after the site is closed (National Solid Wastes Managment Association, 2008).   Concerns regarding the strong odours and exposure to possible toxic gases have been bought to the attention of the council. This report will review the risks and possible health concerns regarding the situation as well as policies and guidelines already in place along with recommendations and management options.

Risks relating to environmental and human health

The environmental challenges associated with post-closure of landfills depends on a variety of factors such as composition of waste, age of waste,  degree of  waste compaction,  climate and most importantly the engineered containment system of the landfill (Victorian Auditor-General’s office, 2014; Cardno Lane Piper, 2014). There are three main concerns that need to be considered; toxins, leachate and gases ( Environment Protection Authority Victoria, 2015) . All of which pose a wide range of environmental and human health risks.  Each a briefly described below.

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–          Toxins: Most landfills consists of varying materials which contains numerous toxins (Environment Victoria , 2013). Over time these toxins are released and seep into the soil and ground water, lasting for several years (Twomey, 2011).  Examples include batteries, old tv’s, computers all of which contains arsenic, acid and lead (Chu, 2008). Mercury is also often found in landfills, and is known to leak from fluorescent light bulbs (Environment Victoria , 2013).

–          Leaching: Leachate is concentrated pollutant liquid formed from rainwater and the breakdown of waste (Young Deuk Kim, 2009).  Leachate contains various toxic organic pollutants, ammonia nitrogen compounds, heavy metals and other complex compounds (ZhaoYoucai, 2018).  Environmental risks from closed landfill is mainly associated with leachate contaminating the water in the soil as well as ground water (Environment Protection Authority, 2018). The generation of leachate in landfills is normal, however can still pose a risk to human health due to it contaminates migrating into nearby environment (ZhaoYoucai, 2018). This would be of particular concerns to the sportsgrounds in which players and groundsmen, would come into direct contact with the soil and are therefore frequently exposed. Furthermore, as well as rainfall, watering of the sportsgrounds may also increase the volume of leachate surfacing along with constant movement of the soil, which could increase the risk of waste-by product migration (Cardno Lane Piper, 2014).

–          Gases: landfill gas is a result of decomposition of waste (Agency for Toxic Substances and Disease Registry, 2001). Methane and Carbon dioxide make up 90% of the landfill gases. Methane gas is extremely flammable, and whilst CO2  is a significant greenhouse gas (Blight, 2011). Ammonia and sulphides more likely responsible for the odour  (Speight, 2019). Table 1 provides a summary of the main components of Landfill gases

Table 1: Landfill Gas components

Gas

Characteristics

Methane

the constituent of landfill gases, will most likely pose the greatest explosion hazard

Carbon dioxide

Cause asphyxiation if their levels are sufficient enough to create and oxygen deprived environment. Additionally, because CO2 is denser than air, Co2  easily collects in enclosed spaces, and due to it’s colourless and odourless makes it difficult to detect. Low concentrations of Co2 may also cause headaches, sweating, rapid breathing, elevated heart rate and dizziness

Nitrogen dioxide

Odourless and tasteless

Ammonia

Extremely pungent and flammable

Sulfides

Causes unpleasant “rotten egg” odours and can be detected even at low concentrations

NMOCs(non-methane organic compounds)

Occur naturally by synthetic chemical process.

Carbon monoxide and Oxygen

Odourless and colourless

(Agency for Toxic Substances and Disease Registry, 2001; Speight, 2019; Scottish Environmental Protection Agency, 2004) 

Surface emission of these gases can also cause community discomfort due to odour and affect people’s general wellbeing (Agency for Toxic Substances and Disease Registry, 2001). Such odours can also cause health concerns such as headaches and nausea (Department of Health. New York Sate, 2012). In addition to this, short term exposure to ammonia and hydrogen sulphide in the air can cause eyes, nose, throat and lung  irritations (Department of Health. New York Sate, 2012).  Furthermore, landfill gases may also carry small traces of carcinogenic  compounds in trace concentrations, raising health concerns for chronic exposure even at low levels (Agency for Toxic Substances and Disease Registry, 2001). Gas levels can change depending on the age, type and quantity of waste and tend to peak within the 10 years after landfill closure (Environment Protection Authority, 2012). The major hazards of landfill gas include flammability, asphyxiation and toxicity (Wilhelm, 1993). Migration of landfill gas to structures and enclosed spaces can accumulate over time (Chu, 2008). Migration of landfill gas is dependent on a number of factors such as

–          Landfill cover type: if the landfill cover is made up of permeable material such as gravel or sand, then gas will most likely migrate up through cover

–          Moisture: Rain and moisture may push out landfill gases

–          Natural and man-made pathway: Drains and trenches may act as conduits for gas movement.

(Miroslav Nasteva, 2001; Agency for Toxic Substances and Disease Registry, 2001) 

Regulatory Guidelines for Australian Landfills

Once a landfill has reached capacity a post closure management plan which includes environmental monitoring and maintenance is necessary to protect the public and its environment (Environmental Protection Authority VIctoria, 2018) . Furthermore, the management of closed landfill sites are crucial to ensure that the environment and community aspirations are met (EPA South Australia, 2019). The following areas require ongoing monitoring after the landfill closed

–          Groundwater: the monitoring of groundwater should be undertaken up until an environmental auditor and EPA are satisfied.

–          Surface Water: Collection and storage systems should be inspected. This is to ensure proper draining and functioning.

–          Landfill Gas: The landfill gas system should be maintained until monitoring systems indicate that generation of gas a decrease

–          Leachate: It’s expected that landfill will continue to generate leachate post closure. therefore regular monitoring is required to show clear trends in leachate generation. Furthermore, inspections after heavy rainfall should take place to ensure management systems are not overloaded.

–          Settlement: most settlements are expected in the first 5-10 years after closure, in which frequent inspection should take place and discussed with an environmental auditor or EPA.

(Golder Associates, 2016; Environment Protection Authority, 2018; Victorian Auditor-General’s office, 2014) 

The Environment Protection Authority (EPA) have established policies and regulatory requirements and  tools; including licences and remedial as well as guidelines for open and closed landfills (Victorian Auditor-General’s office, 2014). These include

–          The 2012 Closed Landfill guidelines

–          The 2010 guideline Best Practice Environment Management Siting, Design, Operation and Rehabilitation of Landfills (the Landfill BPEM)

–          2004 Waste Management Policy (Siting, Design and Management Of Landfills)

–          guidelines for closed landfills and for those exempt from licensing

(Environmental Protection Authority VIctoria, 2018; Victorian Auditor-General’s office, 2014) 

As describe previously there are multiple hazards and risk  that can arise from closed landfills. In order to control such risks,  clause 16(4) of the Waste management policy (Siting, Design and Management of Landfills, No. S264, Gazette 14 December 2004) states that once a landfill has closed, it required by the owners of the landfill to provide notice as to who will undertake ongoing after, up until the landfill poses no risk to humans or the environment (Environmental Protection Authority VIctoria, 2018). After care management is crucial and must include inspection and maintenance of the landfill capping, landfills leachate collection system, landfill gas management system and of surface water control, as well including environmental monitoring system, verified by the an authorised environmental auditor pursuant to the EP Act.

 (Environment Protection Authority, 2018; EPA NSW, 1996)

Unlicensed landfills are generally not regulated, but must comply with landfill policy objectives (Victorian Auditor-General’s office, 2014). However if the landfill is seen as  causing an unacceptable risk,  the EPA can issue a notice to address the risk (Environmental Protection Authority VIctoria, 2018). Compliance, is monitored  by the EPA through inspections, reviews and audits as well as investigations (Environment Protection Authority, 2018).

Older landfills such as the one in Koldwetsoque are most likely built to less stringent standards since the EPA introduced the first landfill policy in 1991 (Victorian Auditor-General’s office, 2014).  Therefore gas and leachate risks are far more complex, timing consuming and costly due to design, siting and past management (Victorian Auditor-General’s office, 2014). This would also include landfill capping. It should be recognised that landfill caps built prior to the first landfill BPEM are unlikely to meet seepage requirements ( Environment Protection Authority Victoria, 2015). Inappropriate and/or incomplete capping of closed landfills can lead to escaping of landfill gas as well as infiltration of rainwater to generate volumes of leachate (Environment Protection Authority, 2012). Therefore these caps need to be assessed and determined whether further construction work needs to be performed in order to meet the standards required (Victorian Auditor-General’s office, 2014). Furthermore, in order to prevent gases such as methane accumulating and migrating to the surface, a membrane and gas monitoring system should be in place with horizontal vents under the slabs/membrane (Department of Health. New York Sate, 2012).

Responsibility of landfill management right up until aftercare is required from the councils, the landfill owners(Victorian Auditor-General’s office, 2014). A series of guidance of materials is available, in order for the council to manage and monitor closed landfills (Environment Protection Authority, 2018). Furthermore the EPA released specific guidelines in 2012 for managing the rehabilitation and after of  landfills that are high at risk (Victorian Auditor-General’s office, 2014).  

Gas and leachate leakage are the main concerns from closed landfill, and therefore are extremely important for councils to have regulatory guidelines in place to manage such risks (Chu, 2008). In order to manage gas leakage, EPA requires all closed landfills to prepare and implement landfill gas risk assessments (LGRA) (Victorian Auditor-General’s office, 2014) .Guidance on completion of an LGRA can be found in the Landfill Licensing Guidelines (EPA publication 1323) (Environmental Protection Authority VIctoria, 2018). The LGRA must aim to increase extraction to prevent causing odours (Victorian Auditor-General’s office, 2014). Moreover, all closed landfills have to meet specific gas limits at the surface (Environmental Protection Authority Victoria, 2019)  . Hydrogeological assessment may also be required to asses the impact of leachate on ground water (Environmental Protection Authority Victoria, 2019).

Discussion and Recommendations

The use of closed landfill for recreational purposes such as sportsground is not uncommon,  however monitoring of the site should constantly take place to reduce environmental and health risks and to ensure the community objectives are met. The main concern of closed land fill is the emission and migration of landfill gases, which poses as the main risk to human health (EPA NSW, 1996). Whilst modern landfills are well engineered to have reliable well controlled gas measures, older landfills such as the one in Koldwetsoque are less controlled/managed and therefore more likely to cause environmental and public harm (Blight, 2011).  It’s up to the owners of the landfill, being the council, to manage after closure risks. However, in order to be able to accomplish this councils will require a high level of inhouse knowledge about the landfill in which the town of Koldwetsoque does not have (Environmental Protection Authority VIctoria, 2018) . Due to poor record keeping of what exactly  was dumped at the landfill, after care and risk management can be difficult. It should be acknowledge by the council of Koldwetsoque, that the closed landfill may not meet the stringent rehabilitation and closure requirements set by the EPA especially for gas and leachate management (Environment Protection Authority, 2018). Therefore the following recommendations are listed below

–          Under the Environmental Protection Act 1970, the council should prioritise and address closed landfill obligations, which should also include

Assessing and managing risks at closed sites

Planning to meet rehabilitation and aftercare costs

(Victorian Auditor-General’s office, 2014) 

–          The council should try and work towards building their inhouse knowledge to be able to work together with the EPA approved environmental auditors and landfill experts in order to effectively priorities, address and manage risks. (Environment Protection Authority, 2018)

–          Develop a prioritised Action Plan and assign risk based priorities to ensure they are actioned appropriately (EPA South Australia, 2019).

–          In order to appropriately asses risks and prioritise  actions, it’s recommended the council works the Environmental Protection Authority a well as regional waste and resource recovery groups (Environmental Protection Authority VIctoria, 2018).

–          It’s important the council ensures community engagement and to work collaboratively stakeholders to be able to effectively address the issue affecting their social and environmental well-being. Community engagement must include regular meetings between community and government bodies, that involve consultations with the community as well information sharing (Environment Protection Authority, 2012). 

–          In order to be able to appropriately evaluate the level of risks from landfill gases at site specific landfill gas risk assessment should be undertaken with appropriate measures for monitoring ( Environment Protection Authority Victoria, 2015). The findings from this will determine the proper management needed for the landfill gas. Guidance on how to complete a LGRA can be found in Landfill Licensing Guidelines, EPA publication 1323 (Victorian Auditor-General’s office, 2014). 

–          Landfill gases must be managed using the appropriate gas containment system, which must be monitored, and at all timed must be managed to prevent offensive odour (Environmental Protection Authority VIctoria, 2018)(Cardno Lane Piper, 2014).

–          An assessment of air toxics should be undertaken as part of the LFGRA. In order to accomplish this a monitoring plan should be developed and implemented (Victorian Auditor-General’s office, 2014).

Conclusion

The odours and community concerns regarding the closed landfill from Koldwetsoque should be addressed by the council. Gas and leachate leakage is off primary concern and  could be the cause for the odours. Due to the historic nature and poor record keeping by the council, regulations regarding closure such as capping and containment systems are unknown, and therefore management of after closure risks may be difficult, costly, and timing consuming. The recommendation and guidelines noted  above should be taken into consideration when investigating and ensuring that risks are prioritised and implemented within a time line. Its is crucial that a landfill aftercare management plan is implemented and monitored up until the site poses no risk to human and environmental health (EPA NSW, 1996). If required the site may be placed on the priority site register (Victorian Auditor-General’s office, 2014) . This will ensure stakeholders as well as the community are aware of the management requirements throughout the entire process (Victorian Auditor-General’s office, 2014).

References

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