Brendan will share his experience from working on the stabilisation works at Witton Bluff. Brendan has been involved in the design process of the stabilisation works, as well as in the role of Project Manager, Superintendent and Site Engineer during the construction phase. His presentation will cover project background information, design issues and considerations, problems encountered during construction and lessons learnt from the project. Brendan graduated with Honours from the University of Adelaide in 1999; has been an employee of Parsons Brinckerhoff since February 2000, and has worked in the field of Geotechnical Engineering for nearly two years.

URS was involved in a groundwater management investigation for Pasminco Port Pirie Smelter at Port Pirie, South Australia to assess the feasibility of using a central dewatering system to manage the offsite discharge of contaminated groundwater. Works centred on a low-lying area of the smelter site excavated into poured slag referred to as the ‘Amphitheatre Pit’. The investigation required the characterisation of groundwater behaviour with respect to flow rates and interaction between natural and slag aquifers and potential tidal influences. Key project activities were a magnetic survey of the area to attempt to locate greater thicknesses of poured slag, and pumping tests to correlate the findings of the survey to available volumes of groundwater. Geotechnical design issues included the magnetic survey and its interpretation, selection of pumping test sites and incorporating these in an overall groundwater management strategy for the site. The outcomes of the investigation provide an interesting example of environmental geotechnics in practice.

Inadequate site investigations can either lead to foundation failures or costly overruns and time delays. However the scope of a site investigation is typically dependent on the budget and time constraints placed on the geotechnical professional. Furthermore, there is currently limited to no information regarding the relative risk of undertaking site investigations of varying scopes. Consequently, a methodology has been developed to quantify the probability of failure or overdesign as well as the financial risk of undertaking site investigations of varying scope. This presentation covered the framework used to assess the influence of site investigations on the design of foundations, in particular, pad footings, as well as some early results obtained from it.