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

   October 2007                                           -8-                                 077682076(AB)


   soils which are not likely to be ASS. The test simulates extreme natural conditions and pH
   drops following this test may not be entirely attributable to pyrite oxidation.

   pHF was measured using a TPS MC81 meter with an intermediate junction electrode
   immersed in a 1:5 soil-water suspension. Soil pHF and pHFOX are summarised in Table C1 in
   Appendix C.

   Some significant variations in soil field pH were noted across the site. The natural soils were
   generally found to range between moderately acidic and neutral with pHF values (natural
   state) typically between pH 4 to pH 7.

   5.4       Summary of Soil Analysis Results

   Table 2 shows the ASS action levels adopted by Queensland authorities based on three broad
   texture categories (QASSIT Guidelines - October 1998). These categories have been used to
   highlight significant results in Table C1, based on the Action Criteria for greater than
   1000 tonnes of disturbed soils.

                                       Table 2: ASS Action Criteria

         Type of Material                        Action Criteria                Action Criteria if more than
                                          1-1000 tonnes disturbed                  1000 tonnes disturbed
   Texture range            Approx     Sulfur trail          Acid trail        Sulfur trail          Acid trail
                                                                   +
  McDonald et al.            clay    %S oxidisable         mol H / tonne     % S oxidisable        mol H+ / tonne
       (1990)           Content      (oven-dry basis)     (oven-dry basis)   (oven-dry basis)     (oven-dry basis)
                             (%)     eg STOS or SPOS          eg, TPA          eg STOS SPOS           eg, TPA
                                                             (or TSA)                                (or TSA)
  Coarse Texture             ≤5           0.03                     18             0.03                  18
Sands to loamy sands
 Medium Texture             5 - 40        0.06                     36             0.03                  18
Sandy loams to light
         clays
   Fine Texture              ≥40           0.1                     62             0.03                  18
 Medium to heavy
clays and silty clays



   The actual volume of soils disturbed at this site will likely be greater than 1000 tonne and
   therefore the lowest action criteria (ie. 0.03% S and 18 mol H+/tonne) are applicable.

   The data quantifying the acid generating potential for soils sampled within the site have been
   collated and are summarised in Table C1, Appendix C, along with laboratory reports.

   Samples with pH drops of 2.0 or more pH units or pH < 3 after oxidisation are highlighted in
   Table C1. From the laboratory test results, SCR % and TAA values above the action levels are



                                              Golder Associates