50 MAREEBA LANDFILL SURFACE WATER MANAGEMENT PROJECT HIGHLY COMMENDED AT 2018 EXCELLENCE AWARDS

Glenda Kirk Director Infrastructure Services, Mareeba Shire Council

The Mareeba Landfill project in February 2019 (12 months post-completion)

Mareeba Shire Council operates landfilling into the environment a regional landfill facility in through aesthetically pleasing Mareeba, Far North Queensland ponds and vegetation. under an Environmental Amy Yates Authority (EA) that imposes Background Senior Environmental Advisor, stringent conditions for the The Mareeba Landfill is located Mareeba Shire Council protection of water quality. on the outskirts of Mareeba, approximately 55 kilometres west The site presents difficult of Cairns. The landfill services the environmental circumstances to region as it is strategically located control erosion and minimise the away from the Wet Tropics, the release of sediment laden waters. coastline and the Great Barrier In 2017, Council undertook a Reef. Domestic waste generated rehabilitation project based on within the Mareeba Shire is sent the principles of soil and water to the Cairns Advanced Resource conservation, which involved Recovery Technology (ARRT) construction of a system of facility which processes residential water harvest areas and an and commercial waste from Morris Hamill overflow polishing pond. These Mareeba Shire, Douglas Shire and Manager Water and Waste, measures have exceeded the the Cairns Region. This facility Mareeba Shire Council original compliance objectives turns the organic component and integrate the functionality of of this waste into commercial

Engineering for Public Works | March 2019 51 compost. The residual waste is sent to Mareeba Landfill and a privately-operated landfill in Mareeba Shire. The Mareeba Landfill site sits on the watershed boundary between river catchments for the east- flowing Barron River and west- flowing Mitchell River. Sitting at the head of the catchment, surface waters flow from the site to the Barron River and ultimately to the Great Barrier Reef. Sediment loading in Far North Queensland's rivers is a scientifically recognised pollutant contributing to a decline in water quality and is considered to be a major cause of the current poor state of many coastal and The Mareeba Landfill project in December 2017 (during construction) marine ecosystems within the Great Barrier Reef. As a Reef Guardian Council, Mareeba Shire Council maintains a commitment to protect and conserve the Reef through its activities. Development The Mareeba Landfill operates within a highly sodic soil environment. Sodic soils are notoriously difficult to manage due to their dispersiveness. These soils are susceptible to chemical erosion on contact with rainfall. When eroded, sediment can remain suspended in the water column for many weeks. Therefore, suspended solids discharged in sediment laden waters leaving the site had the potential to be The Mareeba Landfill in December 2015 (before) transported for many kilometres before settling out. discharged from the site. Council mid-2017 that outlined objectives, submitted a voluntary Program actions and milestones and permit Despite using heavy hydromulch Notice under the Environmental Council to transition to compliance to cover exposed areas of interim Protection Act 1994 as a strategic in readiness for the 2017 - 2018 capping and implementing other compliance action following a wet season. general erosion control measures, number of non-compliances during Mareeba Shire Council had the 2016-17 wet season. This led Whilst the use of standard erosion been unable to comply with the to the successful negotiation with and sediment control measures Environmental Authority which the State environmental regulator such as check dams, sediment imposes stringent suspended to enter into a Transitional fences and hydromulch would solids limits in the surface waters Environmental Program (TEP) in have fulfilled Council's General

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Environmental Duty, they most likely would have failed over the long-term due to the nature of the in-situ soils and rainfall climate. Council identified that a treatment solution must exist that would service the landfill into the after- care period and would require minimal operational investment. Implementation Council engaged a Certified Practitioner in Erosion and Sediment Control (CPESC) to develop a Surface Waters Management Plan for the site. The CPESC program is administered The Mareeba Landfill project was highly commended at the 2018 IPWEAQ Excellence by the International Erosion Awards. Control Association Australasia and represents industry best compliance point. completion of this project offers practice in erosion and sediment some regulatory comfort to the control. The provision of a surface The construction works were administering authority in relation waters management plan to a completed in late 2017, prior to the use of TEPs as a compliance CPESC standard is beyond the to the wet season. A post- tool. TEPs provide the opportunity requirement of the EA, however commissioning review was for local governments to partner Council wanted certainty of undertaken in early 2018 and with the regulator to transition to achieving a sustainable compliance confirmed that the objectives an agreed environmental standard solution within the TEP timeframes. under the TEP had been met in full. using a statutory mechanism, free The Surface Waters Management Outcomes from penalties. Plan identified the sources of The Surface Waters Management The project has resulted in sediment laden waters and the Project has rehabilitated the a dramatic improvement of environmental risk of erosion landscape and improved the suspended solids in the waters from those areas. Risks to the functionality of surface waters discharged from the site from over environment were fully managed treatment at Mareeba Landfill 1000mg/L prior to the work to by applying the best practice by minimising exposed ground, less than 50mg/L. Implementation principles of drainage, erosion providing gentle controlled of a Surface Waters Monitoring and sediment control and then drainage and managing sediment Program continues to be used to implementing the resultant design transportation offsite. The verify the effectiveness of those detailed in the Surface Waters system achieves and exceeds the controls and and the project Management Plan. The main regulatory requirement whilst has immeasurable benefit by principles were to minimise the requiring nothing more than creating awareness in the wider amount of exposed soils, maximise visually monitoring the landform local government Reef Guardian groundcover and significantly integrity and removing a layer of community. increase the retention time geotextile on the rock filter check to settle solids in stormwater. dam each year until vegetation is The result is an aesthetically Measures included the protection substantially established. pleasing stormwater management of landfill batters, construction of system that functionally integrates water harvest areas designed to Council’s partnership with the environmental protection with an cater for a 1 in 10 year, 15-minute State environmental regulator has operational landfill and ultimately rainfall event, a water polishing been instrumental in the success protects the waterways and the lagoon and a rock filter dam at the of this project. It is hoped that the Great Barrier Reef.

Engineering for Public Works | March 2019