EGL Ref: 9215 23 June 2022 Page 23 This report shall only be read in its entirety. File: WAI-985-000-REP-LC-0002_Rev0.docx. The general embankment zoning system is illustrated in Figure 16 and works as a system by providing low permeability zones on the upstream, downstream and base of the embankment. Each zone of the embankment is constructed from specifically selected material that comes from the pit and is compacted to specific standards to achieve the different objectives of each zone. The different zones and their objective are summarised below. FIGURE 16: ILLUSTRATIVE CROSS SECTION OF EMBANKMENT ZONES Zone A - A low permeability zone at the base of the embankment, made of tightly compacted earth and rock that restricts leachate seepage from the waste rock into the underlying ground. As this layer is in contact with the environment, this layer is non-acid forming (NAF) material. Zone B - A low permeability zone on the upstream face of the embankment which is in contact with the tailings. It is made of tightly compacted earth and rock that restricts leachate seepage from the tailings into the embankment. Zones C - A structural fill zone that provides support to Zone B, by providing a transition between the finer grained material in Zone B and the coarser material in Zones D. Zones D & E - A bulk structural fill zone that accepts the majority of the waste rock, with compaction requirements for stability. This layer contains the majority of PAF material. Zone F - Structural fill zone on the outside shoulder that provides a transition between the coarser material in Zone D and finer material in Zone G. Zone F also provides a drainage path for leachate. Zone G - Sealing layer on the outside shoulder of the embankment that restricts entry of oxygen and water into the waste rock. This restriction limits the generation of acid leachate by slowing the geochemical reaction. As this layer is in contact with the environment, this layer is created using non-acid forming (NAF) material. Zone H - Plant growth layer on top of Zone G. This layer is effectively an extension of the upper part of the Zone G layer, which is then ripped to promote plant growth. Topsoil - Topsoil layer placed for pasture and plant growth on top of Zone H. These zones work together with a leachate collection system. Both the ponded water and seepage/leachate is collected, piped and treated at the wastewater treatment plant.
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