Our contaminated sites team have had a long and detailed involvement assisting the THIE come to fruition. The scope of services that Strategen provided for this project includes:
Strategen achieved auditor sign-off for three separate site management plans, and held consistent and comprehensive liaisons with DWER.
Strategen completed initial Acid Sulfate Soil investigations in 2016 for the Madox residential subdivision in Piara Waters and continues to provide ongoing Acid Sulfate Soil management for this 29 ha residential subdivision development. The site was highly constrained due to the presence of a high-water table adjacent to a Conservation Category Wetland, was waterlogged during winter months and had previously been significantly filled.
Two sources of Potential Acid Sulfate Soils (PASS) – Coffee Rock and Peaty Sand – were identified as extending across the entire site. Strategen prepared and supervised the implementation of an Acid Sulfate Soil and Dewatering Management Plan (ASSDMP), conducted the required groundwater, dewatering and lime treated soil sampling and prepared close out reporting in accordance with the Department of Water and Environmental Regulation (DWER) guidelines.
The development required the installation of deep sewer and other services, necessitating the excavation of PASS, which was treated using imported lime. The treated soil was validated through a soil sampling and analysis program. The validated treated soils were re-used onsite.
Large volumes of dewatering was required to allow the construction of sewer trenches, resulting in the drawdown of the groundwater, further exposing PASS to air.
Strategen developed a groundwater model to predict the likely onsite and offsite drawdown impacts and devised a holistic site management approach placing dewater infiltration basins in areas to offset potential drawdown impacts. This assisted the engineer in the tendering of site works and the overall management of the earthmoving contractor. The model was also used to assist in obtaining a licence to take superficial groundwater for the irrigation of a public open space.
Acid Sulfate Soil Initial Closure Reports (ASSICR) have been prepared, submitted and approved by DWER for several stages of the development. Once completed, the information will be collated into a close out report and will be used to clear the condition of subdivision related to Acid Sulfate Soils.
For the past 3 years, Strategen has been the environmental superintendent for the re-development of the Midland Railway Workshops by the Metropolitan Redevelopment Authority (MRA). The former railway workshops manufactured and maintained rail cars and locomotives for almost 100 years. Strategen have successfully managed the remediation of various contamination issues and rationalised approvals for this complex site.
The site contains uncontrolled fill containing foundry waste, cinder, slag and asbestos. Hydrocarbons including diesel, oil and coal were stored onsite. Contaminants in soil and groundwater include heavy metals, total petroleum hydrocarbons, Benzene, Toluene, Ethyl Benzene and Xylene, polycyclic aromatic hydrocarbons, volatile organic compounds, poly-chlorinated bi-phenyls and asbestos. Large quantities of contaminated material are stockpiled at the site and large amounts of contaminated fill remain onsite.
Strategen have undertaken the following tasks:
Past waste management practices were not up to today’s standards and there has been a long history of use. The key challenges have been:
The project is a mixture of high density and commercial use and demonstrates Strategen can successfully manage investigations and remediation for complex contaminated sites.
Strategen were engaged to undertake groundwater investigations, direct site decommissioning and complete soil remediation at a retail service station site in rapidly urbanising Piara Waters.
The site was utilised as a service station for approximately 40 years prior to recent government compulsory land acquisition to facilitate interchange upgrades as part of $145M Armadale Road upgrade works.
All site underground petroleum storage systems (UPSS) required removal, with identified contaminated soil to be remediated to mitigate potential risks to personnel involved with the upgrade works.
The presence of shallow groundwater beneath the site meant that dewatering will be required during civil works; groundwater investigation was required to ascertain groundwater quality and determine the appropriate management and discharge strategy for dewater effluent.
Strategen successfully implemented a soil remediation and validation program leaving the site suitable for the proposed land use, with soil validation results demonstrating that no adverse risks to future site visitors or civil workers exist via direct contact with soil contamination or inhalation of hydrocarbon vapour.
Further, Strategen directed the appropriate offsite disposal of excavated contaminated soil, and characterised the vast majority of excavated overburden as suitable for reuse on site, saving the client a significant amount of money associated with added disposal costs and importation of clean fill.
Strategen liaised closely with the Metropolitan Road Improvement Alliance (MRIA) throughout the planning and project implementation phases.