Petroleum Import Facility

Background

To increase local supply and distribution of oil products Puma Energy proposed to help construct a Tank farm capable of storing nominally 220 ML of Diesel and Petroleum. A total of 20 Storage tanks were proposed within the facility, with applied loads of nominally 170kPa to 270kPa.

The subsurface profile at the site was typically 10m to 20m of calcareous sand overlying variably leached Tamala Limestone. Tanks previously constructed on the calcareous Safety Bay Sand of the Kwinana Industrial area have experienced significant long term creep settlements, particularly associated with the cyclic unloading and reloading of the tanks.

Scope

CMW carried out a geotechnical investigation for the project area and completed the following:

Drilling supervision for 4 cored boreholes up to 30m deep. Monitoring wells were also installed in the boreholes;
Supervision of 18 Cone Penetration Tests (CPT) probes up to 22m deep, and 2 Seismic CPT probes;
Supervision of 10 test pit excavations; and
Electric Resistivity testing at 6 Locations.

Findings/Challenges

The tanks were required to operate within very low settlement tolerances (less than 20mm). With the specialist insitu measurements and regional knowledge of the behaviour of calcareous sand, CMW were able to better estimate elastic and creep settlements. CMW identified a number of lower cost ground improvement options in addition to the originally proposed piled foundation option.