Appendix 5. Geotechnical Engineering Report [As Published] · 132007.2399

    October 2007                                     -6-                           077682076(AB)


    4.4        Geotechnical Laboratory Testing

    The results of geotechnical laboratory classification testing carried out are given in Appendix
    B and are summarised in Table 1 below.

                Table 1: Summary of Geotechnical Laboratory Classification Testing

Borehole #       % <0.075 mm    Liquid Limit   Plastic Limit    Plasticity       Linear        Emerson
(Depth, m)        (Silt/Clay)       (%)            (%)         Index (%)       Shrinkage         Class
                                                                                  (%)           Number
BH1, 0.3-0.4          3              -               -              -              -               6
BH3, 0.4-0.5          9              -               -              -              -               8
BH4, 0.3-0.4          5              -               -              -              -               8
BH5, 0.2-0.3          64            53              16             37             14.5             -
BH6, 0.5-0.6          2              -               -              -              -               -




    Geotechnical laboratory testing generally confirms our field descriptions of the sands and
    clays encountered in the boreholes. Emerson class numbers of 6 to 8 indicate that the soils
    tested are non-dispersive.


    5.0        ACID SULFATE SOILS

    The development of Potential Acid Sulfate Soils (PASS) is commonly the result of marine
    and 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 material
    produces acidic conditions and oxidation typically occurs as the material is exposed above the
    water table by excavation.

    Previous experience and available guidelines indicate that PASS are normally restricted in
    extent to recent (Holocene to Pleistocene age) soil horizons deposited in a saline environment
    below RL 5 m AHD. The State Planning Policy SPP2/02 Planning and Managing
    Development Involving Acid Sulfate Soils applies to land, soil and sediment at or below RL
    5 m AHD where the natural ground level is less than 20 m AHD. Within such areas the SPP
    applies to development involving any of the following:

    •     Excavating or otherwise removing 100 m3 or more of soil or sediment; or

    •     Filling of land involving 500 m3or more of material with an average depth of 0.5 m or
          greater.


    The topography of western part of this site is consistent with the above criteria (Ref. Figure
    No. 1 for RL 5 m AHD contour). Furthermore, the proposed development will involve




                                           Golder Associates