Project Overview
Soil bioremediation of site contaminated by 500,000 litre oil spill.
Penrice have been occupying their Osborne site for the last 80 years, undertaking a wide range of activities involved in the processing of soda ash and sodium bicarbonate.
McMahon Services was engaged to bioremediate soils within the area of a former above ground storage tank for fuel oil and existing underground storage tanks. The bulk of the contamination resulted from a 500,000 litre fuel oil spill that occurred on the site in the 1970’s.
Excavated contaminated material was treated in a series of purpose built biopiles. These biopiles were made up of the following constituents:
The biopile design focussed on a negative forced aeration system. This approach ensures that odours and potentially environmentally sensitive receptors were not negatively impacted. The contaminated soil was utilised with a number of amendments to ensure the prevailing environmental conditions were conductive to optimised metabolic activity. This included adding in green waste to increase porosity for efficient out flow adding in a range of nutrients specially designed for microbial growth. The enhanced bioremediation system was then ready for construction.
The construction proces included series of leachate and condensate collection lines were installed on top of an on-site welded HDPE liner. These pipes were reticulated to a series of manifolds, then further reticulated to a purpose-built carbon filtered air extraction and filtering system.
The vacuum system comprises a 3,000 litre pressure vessel acting as a moisture trap, a 3,000 litre capacity carbon filter and a purpose built roots vacuum blower. The entire vacuum pump system was installed on a skid-mounted platform for easy maneuverability on-site. The contaminated soil was mixed on a purpose made mixing pad to form the biopile. Once the biopile was constructed to sufficient capacity, a series of water dripper lines were installed and the HDPE cover installed and welded in place, providing an air tight envelope.
The project team successfully managed several challenges, including:
- Undertaking well point dewatering for excavation of contaminated material
- Monitoring of dewatering water to ensure only ‘clean’ water was removed, without effecting the contaminated plume of underground water
- Working within a fully operational site
- In-house design and construction of the unique vacuum system
- Sourcing quality materials in the quantities required
