The referral received by the EPA is for the construction and operation of the stadium. The EPA considers that the main environmental issues are associated with the pre-construction site works, which will stabilise and prepare parts of the site before the main construction phase. The site was previously used as a landfill facility and has been classified as "possibly contaminated - investigation required" under the Contaminated Sites Act 2003. Preconstruction site works will effectively compress the unstable fill layer, which has resulted from historical use as a landfill. Surcharging techniques will be applied, where clean fill is placed to load the ground and compact the site. Wick drains will also be installed to increase the rate that groundwater drains from the Swan River Alluvium soils beneath the fill layer. Once settlement is achieved, excess clean .fill will be removed.