Carnarvon, Western Australia
Background
Western Power proposed to construct a $73 million, 18 megawatt dual-fuel (diesel and gas) power station, located approximately 6.5km east of the Carnarvon town centre to serve the needs of Carnarvon and the Gascoyne region. The power station development proposed for the approximately 5.4 hectare site includes tanks, generators, transformers, pump skids and gas receiving skids.
Western Power had previously commissioned two geotechnical site investigations for the project. These investigations did not provide sufficient geotechnical information to the structural engineer (GWB Plant) for detailed design due to the presence of collapsible soils (Pindan sands) nor did they quantify the collapsible soil risks.
Scope
CMW completed a desktop study based on the existing geotechnical information. Preliminary design parameters, for deep and shallow foundation options and recommendations for further site investigation to confirm ground conditions were developed and documented. The effects of transient loads such as wind and machine loads were also considered for shallow foundation options.
Based on the desktop study, further geotechnical investigation works were carried out to assess the presence and extent of collapsible soils. The investigation included in-situ plate load testing in dry and saturated conditions, and double odometer laboratory testing.
Following insitu and laboratory testing, CMW provided a number of foundation and ground improvement options for the various proposed facilities.
Findings/Challenges
Based on the more rigorous collapse potential testing carried out as part of our investigation, a less conservative approach to ground remediation was provided.
In order to mitigate risks of ground collapse, a mixture of deep and shallow foundation options was recommended for the various structures and loads. Ground improvement was also provided as an option, and was recommended for areas of the site supporting larger vertical loads.
Information was provided by the client in the form of both interim and final reports to meet the project programme.