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

October 2007                                    - 11 -                            077682076(AB)


In particular the following measures apply to the liming process:

•   Treatment should be carried out on prepared pads which may be the permanent
    placement area. The earthworks strategy should be formulated to provide a number of
    pads of appropriate size for practical spreading mixing and drying, so that adequate time
    is available to complete the treatment and validation testing before placing the next layer.

•   Treatment pads are to be contained by bunds with stormwater runoff directed to a
    collection sump. Bunds to be constructed from low permeability materials that are not
    ASS or have been fully lime treated.

•   The treatment pad should be stripped of topsoil and proof rolled to achieve a uniform
    density and reduced permeability, then a guard layer of neutralising agent should be
    spread across the soil surface prior to placement of the first layer of fill. The rate of
    neutralising agent applied should be based on 0.2 times the average total potential plus
    existing acidity for every 1m depth of fill placed. For preliminary purposes an
    application rate of 5 kg lime per m2 per vertical metre of fill thickness is suggested.

•   Treatment should be carried out by spreading the soil in maximum 300 mm loose
    thickness layers and moisture conditioning before spreading lime at the appropriate
    application rate. The ASS may require reworking several times to achieve adequate
    mixing of the neutralising agent and/or drying of the soil.

•   It is proposed that treatment levels are assigned on the basis of the results of a detailed
    ASS investigation. Liming rates from this preliminary investigation would be as follows:

    o    Existing fill/pale coloured soils               10 kg lime/m3

    o    Natural dark coloured clayey sands              50 kg lime/m3

    o    ‘Marine’ clay                                   100 kg lime/m3

    Lime treatment rates should be confirmed following further investigation, together with
    inspection and field testing by a suitably qualified and experienced environmental
    scientist during excavation.

•   Verification sampling and analysis is to be carried out on the treated soil using the
    Chromium suite method at a rate of 1 test per 250 m³ to confirm that appropriate amounts
    of the neutralising agent have been incorporated into the soil.

•   An accurate spatial tracking system should be developed to control the movement and
    final location of the treated soils so that initial testing (from this report) can be correlated
    to the verification of prescribed treatment.




                                      Golder Associates