It was proposed to stabilise the impacted soils by the mixing of the soil with selected reagents to break down and bind up contaminants of concern, in order to minimise risks to health and the environment, commensurate with ongoing industrial use of the land. Validation sampling and testing as well as the storage and treatment of excavation dewatering liquid was carried out by the Environmental Consultant.In order to treat the impacted material a unique (to South Australia and possibly Australia) short term processing plant had to be implemented.
The process involved the excavation of 4,100 cubic metres of impacted soils from eight separate areas to varying depths from 3 metres to 6 metres. As part of the excavation of the impacted soils, some 5,200 cubic metres of clean soil was excavated and stockpiled for re-use as a cover to the treated impacted fill.
Unique Process
The project was unique in its concept for the treatment and stabilising of impacted soils, with the use of the Reterra soil conditioning machine. The process consisted of adding numerous dry and liquid reagents to the soil and then creating a slurry for re-use on site. Odour monitoring was carried out by Soil and Groundwater Consulting and Tonkin Environmental Consulting employees. Dust monitoring was carried out on a daily basis by the use of DustTrak monitoring equipment.
Extra Measures
A wheel wash was installed on site for any vehicles that required cleaning prior to driving on public roads to ensure no contaminated soils were removed from site. Haul road for on site vehicles and separate clean areas for off site vehicles were designated. Stormwater was prevented from leaving the site by the use of bunding where required and silt socks and hay bales were installed at stormwater side entry pits.
McMahon Services completed the project on time, on budget with zero safety and environmental issues or complaints and to the total satisfaction of Incitec Pivot Limited. The site was visited by the Environmental Auditor on a number of occasions to check that the remediation works were being carried out as per the Remediation Plan and the Technical Specification. There were no non-conformances with regard to any environmental issues under the control of McMahon Services.