J000154-001-R-Rev0_ASS Investigation Report · RAP15/0034

J000154-001-R-Rev0                                                                                 November 2015


1.0     INTRODUCTION
This report details the results of an acid sulfate soil (ASS) investigation carried out by Core Consultants Pty
Ltd (Core) for a proposed residential development at 47 Witta Circle, Noosa Heads (the Site). The
investigation was undertaken at the request of SCG Consulting Engineers (SCG).
The ASS investigation was undertaken in order to assess the extent and severity of ASS materials across
the site which may be at risk of disturbance by the proposed residential development (primarily excavation of
the basement carpark). This report details the results of the above investigation and includes
recommendations regarding the extent and management of ASS.
The investigation was undertaken in accordance with the State Planning Policy – State Interest Guideline
‘Water Quality’ (August 2014).

2.0     PROPOSED DEVELOPMENT
Information provided by SCG indicates that the proposed development will comprise a single storey
residential dwelling over a single level basement carpark. Excavations for the single level basement carpark
are expected to extent to depths of approximately 2.5 m below existing ground level (bgl).
3.0     SITE DESCRIPTION
The site is approximately 616 m2 in area and is bound by Witta Circle followed by residential houses to the
north, residential dwellings to the east and west and Weyba Creek to the south. Weyba Creek flows directly
into the Noosa River and the Coral Sea, and is subjected to the associated tidal fluctuations.
It is understood that the site was filled with dredge spoil during excavations of Weyba Creek in the 1970’s.
However no information about possible ASS treatment or verification of the dredge spoil could be found. At
the time of the investigation the site was vacant (refer Plate 1 below).




Plate 1: General Site Conditions looking south

4.0     ACID SULFATE SOIL OVERVIEW
The development of ASS is commonly the result of marine or estuarine deposition of sulfate and iron bearing
sediments in the presence of an abundant source of readily decomposable organic matter resulting in the
deposition of pyrite. This pyrite is stable within the soil so long as anoxic conditions prevail. Oxidation of this




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