Lake Coogee - Geotechnical

The Lake Coogee development is a 230 lot subdivision on 30ha of land located in Munster. The site was on an old market garden site that was developed into a residential estate. The development was carried out in three stages, each consisting approximately 70 lots, completed in March 2012. Pritchard Francis personnel were responsible for the removal of contaminates and remediation, ground improvement and civil engineering aspects of the project from the beginning of the development through to delivery of titles. This site was fully serviced with roads, drains, sewer, water, power, communications, gas and a Water Corporation’ sewer pump station.

The site consisted of pinnacles of limestone, high water table levels and loose uncompacted sand. An initial geotechnical report recommended all loose sand material be excavated to a depth of about 8-10m and be replaced and re-compacted in 300mm layers to obtain the required compaction to achieve a Class A site as required by the City of Cockburn. Alternative methods of achieving a class A site were investigated from which it was decided to engage a specialised contractor that had the equipment capable of compacting material in place at great depths thereby avoiding deep excavations and environmental issues. A Class A site classification was achieved at a much lower cost than removal and re-compaction of loose material and the construction time was reduced by several months.

Installation of dual sewer systems were negotiated with the Water Corporation to reduce the extent of dewatering and to reduce impact on the environment. Even though it meant more sewer had to be installed the final cost of this work was less due to the reduction in the amount of dewatering required and avoided lowering the water table which would have had adverse impact on the surrounding area.