2 David Low Way - Attachment 4 - Specific Engineering Assessments - Cardno 10-8-17

753345 5
9 August 2017

Acid Sulfate Soils

The northern part of the site is shown as being in the low potential acid sulfate area (5-20 m AHD).
There is no reason for this designation other than the existing level of the land. As far as | am aware,
no acid sulfate soil investigations have been carried out on the site. It is my opinion based on site
inspection and review of available data that the site basically consists of a prehistoric sand dune which
was formed when the ocean water level was significantly higher than moder times. A further two dune
systems are evident in the area between the site and the current beach location, indicating additional
dune areas which have been abandoned as water levels fell over the past 10,000 years. It is most
likely that the sub-surface stratigraphy consists of clean beach sand formed under aeolian processes,
similar to that which is evident at the surface and in the dune profiles. On that basis, it is most unlikely
that acid sulfate soils are likely to be present on this site.

Further, it is not proposed to carry out any subsurface excavation other than to potentially level the top
of the site to create building platforms. It is possible that the dwelling houses to be constructed on site
will be piled for structural purposes. Any material below 10 m AHD which is disturbed during the
construction process will be tested for acid sulfate potential and treated accordingly.

Geotechnical Assessment

The site is shown as being land-slide prone under the Natural Hazards Overlay in the Planning
Scheme. In that context, there is a requirement to assess the application under the relevant Natural
Hazards Code in Part 13 of the Scheme.

The specific requirements of that Code are as follows:

O7 Development is located to ensure it does not compromise the safety of people, property or
hazardous materials manufactured or stored in bulk by increasing risk of landslide;

AND

O2 Development, including access ways is designed and constructed to—

a) minimise impacts on the natural landform;

b) minimise risk to people and property from landslide;

c) avoid any potential instability and associated problems, including long term stability of the site
and long term stability of the development.

Planning Scheme Policy PSP1 sets out the information that Council may request in relation to a
development application. For development in areas identified as having Landslide Hazard Potential on
the Overlay Maps, PSP1 requires a site-specific geotechnical analysis to consider the long-term
stability of the site, and the long-term stability of proposed development.

The potential for geotechnical instability to be present on the site has therefore been assessed by site
investigation by an experienced geotechnical engineer. The findings of this investigation are included
herein as Appendix D. It was determined that the site is not subject to geotechnical instability in its
current state, and the proposed development will not affect geotechnical stability.

CAUsers\trevor johnson\Documents\castaways.docx