White Rock Quarry (Hanson)
Due to heavy rainfall during July 2021, sediment from the White Rock Quarry has entered Third Creek.
The Department for Energy and Mining (DEM) is the lead regulator of the White Rock Quarry, and together with the EPA, has undertaken compliance actions in regard to this sediment runoff.
Hanson Construction Materials Pty Ltd (Hanson) must achieve the compliance objectives and conditions of the mine operations plan (MOP), which is regulated by DEM.
These objectives are not being achieved at present, and DEM and EPA jointly took compliance action on 20 July 2021 with the intent of reducing the level of sediment leaving the site.
Winter 2021 rainfall and the impact on Third Creek
Higher than average rainfall has been received in July this year. This has resulted in all creeks in the region to flow faster and caused a normal or natural increase to turbidity of the creeks, which means they will change colour due to surface erosion from a number of sources.
Stormwater pollution from multiple sources also impacts on the creeks and collectively impacts on receiving waters. Urban stormwater runoff, for example, is also a significant sediment source.
Highly turbid (coloured) water has entered Third Creek from both the White Rock Quarry and sources such as public roads.
Surface water management
Despite there being a number of sources of sediment to Third Creek, DEM and the EPA are responsible for regulating sediment discharges from sources such as the White Rock quarry. There are specific surface water criteria outlined within the MOP whichHanson is required to comply with.
There is also an environment improvement program (EIP) in the EPA licence that requires Hanson to undertake a range of short, medium, and long term actions to improve stormwater quality and reduce sediment discharge off-site.
The EIP was developed in 2017 in line with the Environment Protection (Water Quality) Policy 2015. There is also a water monitoring program stipulated in the licence which requires Hanson to engage independent consultants to conduct continuous water quality monitoring at the site. This data must be reported to the EPA on a quarterly and annual basis, the results of which inform the effectiveness of existing and recently implemented management measures.
Operations at the quarry must be in compliance and the EPA works with DEM to inform regulatory actions when standards are exceeded.
The topography of the site is complex and surface water management is challenging. However, EPA and DEM are committed to ensuring Hanson takes all reasonable and practicable measures to reduce its off-site discharge and impact.
Hanson is required to demonstrate compliance with the environmental objectives for water quality.
Action required over the next 12 months
The EPA and DEM has been engaging with Hanson regarding surface water management during high rainfall events at White Rock Quarry for over 10 years. While significant improvement has been made by Hanson including (but not limited to) diversion of conservation park clean flows, site drainage and sediment capture structures, and construction of Sediment Basin 1 to treat stormwater, further management actions are required, and Hanson is in the process of implementing these. The EPA and DEM will continue to monitor the effectiveness of any new management measures and will continue to require further improvement until the objectives of the MOP and EPA licence are achieved.
Sediment control is an important part of protecting the aquatic environment. The EPA and DEM require Hanson to continue to monitor sediment run off and implement further measures to control run-off to the creek system.
This includes a requirement for Hanson to investigate and implement additional engineered controls of stormwater and to improve water treatment over the next 12 months.
Sediment discharges and the proposed expansion
While Hanson is working toward bringing the current operation into compliance through investing significant money on the sediment control measures, the EPA is scrutinising the proposed expansion, which DEM is responsible for assessing in accordance with the Mining Act (1971), to ensure any proposed changes to operations will allow further improvements to surface water quality.