07/1586 - Response to Information Request [As Published] · 132007.1586

* Project No. 307-2624 Page 6
August, 2007

 

Various neutralising agents are available, however agricultural lime or “aglime" (CaCOs)
is considered to be the most suitable, being the most widely available and least

hazardous product for acid sulfate soil treatment.

The application of aglime to the soil requires thorough mixing and incorporation into the
soil. As a general approach it is recommended that careful supervision and control of the
excavations are carried out. Further, that sampling and testing of the materials should
be carried out during excavation, to confirm the effectiveness of the acid neutralisation.

The appropriate application rate for the aglime is calculated using the formula presented
in ASS Tip 13 in the Queensland Acid Sulfate Soi! Technical Manual - Soil Management
Guidelines, where the rate of CaCQs; in kg/tonne is calculated as 46.8 x %S (Scr) or
0.075 x mol H*/tonne (TAA). This rate incorporates a 1.5 factor of safety on the quantity
of aglime.

It is calculated that neutralisation of the excavated silty sand at this site should be
carried out with aglime applied at a rate of 3.5kg/tonne, which is equivalent to
5kg/m*(with a dry density of soil = 1.5tonne/m*).

It is recommended that the acid neutralisation procedure incorporate the following
measures to ensure an effective result is achieved:-

* Only aglime (CaCOs) should be used, as quick lime (CaO) or slaked lime (Ca(OH)2)
are not considered viable or safe long-term neutralising agents of acidic soil.

« The recommended lime dosing rates refer to a 100% pure lime product. The actual
liming rates would need to be factored according to the product's quoted
neutralising value in order to reach the ideal neutralising capacity.

* The aglime should be fine grained to ensure better mixing and decreased chance of
acid leachate runoff occurring.

* The aglime should be thoroughly mixed with the acidic soil prior to disposal or

re-use.

The recommended design liming rate is calculated to neutralise the recorded worst case
acid sulfate soil as revealed by the sampling and testing. As noted above, treating the
excavated soil from this site with aglime at the above rate can be considered a
precautionary procedure; since the worst (and only) case acid sulfate soil sample was

retrieved from below the expected maximum depth of excavation.

 

ZF SOIL SURVEYS ENGINEERING