The rehabilitation area consisted of approximately 100 ha with a significant fall of approximately 100 m (average ˜10% slope) from the top of the catchment to the discharge point. During bulk earthworks, final profiling and the early stages of revegetation a number of erosion and sediment controls were implemented with a sediment basin required prior to the discharge point to capture sediment mobilised from the rehabilitation area and prevent non­compliant discharges. Using a traditional approach to sediment basin sizing, a basin volume of approximately 80 ML would have been required, which due to its size, would need to be a permanent feature of the final landform.

A HES basin was considered as an alternative to a traditional sediment settling basin and modelling found that it offered a much smaller volumetric requirement, with an improved proportion of stormwater treated and allowed a flow­through approach rather than batch capture and treatment of stormwater.

The Oakleigh West Pit was actively mined as an open cut operation until 2013 with progressive rehabilitation being undertaken as areas became available. Following the cessation of operations, ongoing rehabilitation work has been undertaken on the remaining mined areas.

Over a period of several years the open cut void was progressively backfilled with spoil in order to create a permanent free­draining final landform that is similar to the pre­mining topography, representing current best practice in mine rehabilitation.