PASS, page-90

From your link

"An estimated 2,033,500 m³ of spoil would be generated by the construction of Melbourne Metro (approximately 613,000 m³ from the tunnels, 104,200 m³ from the portals and 1,316,300 m³ from the stations). Of this, it is anticipated that 1,349,300 m3 would be clean fill."

That leaves (2,033,500 - 1,349,300) = 684,200 m3 x 2.41 (ms to tonne ratio) = 1,648,922 tonnes of non clean fill

During construction of Melbourne Metro, for all precincts, there would be limited opportunities to re-use excavated clean fill on-site. This spoil would have to be removed off-site as a waste or be directed for re-use at another site – a positive outcome from the project. Potential re-use would be subject to further testing to determine the final waste classification and geotechnical suitability of this spoil, in accordance with EPA regulations and guidelines.

20.7.3 Acid Sulfate Soil and Rock

As noted in Section 20.5.3, there is a high likelihood of Melbourne Metro encountering potential and actual acid sulfate soil and acid sulfate rock. This means that a high proportion of the spoil excavated from the tunnels (about 221,000 m³) would be expected to be acid sulfate soil or acid sulfate rock. The potential impacts from disturbing acid sulfate soil and acid sulfate rock include human health impacts, adverse effects on aquatic environments and the corrosion of concrete and steel infrastructure from acidified groundwater.
Acid sulfate impacts would be managed in accordance with EPA guidelines and the Industrial Waste Management Policy (Waste Acid Sulfate Soils). This would include implementing an environmental management plan that includes:

• • • Identification of the location and extent of any acid sulfate soil and rock (primarily Fresh Melbourne Formation rock and Coode Island Silt) within the project boundary Assessment of the potential environmental risks of disturbance
Identification of suitable sites for the re-use or disposal of any acid sulfate material.
Prevention of acid generation is the preferred management option.
However, a number of off-site waste management options are available for treating acid sulfate material extracted during tunnelling activities, where prevention is not possible.
These options include:

-Treating spoil with limestone

-Inhibiting oxidation of pyrite in spoil by underwater disposal or by encapsulation within a water saturated engineered cover

-Preventing leaching of pyritic spoil by encapsulation within a long-term containment system designed to limit infiltration.

Further testing would be undertaken during the project’s detailed design and construction phases to determine the most effective management option.

Acid sulfate soil can only be disposed of or re-used on sites that have an EMP approved by the EPA or at a landfill with the appropriate licence. On-site re-use of this material is not considered practical.



221000 m3 or 532,000 tonnes from tunnels alone
then you have to add in 5 stations and portals

So how much lime will they need will depend on the acidity of the soil

• Lime needed (kg CaCO3/tonne soil) = net acidity (kg H2SO4/tonne of soil) x 1.028 x safety factor9 x 100/ENV10
As net acidity is most commonly reported in units of percentage sulfur (S%), the equation is rewritten below using S% units:
• Lime needed (kg CaCO3/tonne soil) = net acidity (S% x 30.59) x 1.028 x safety factor9 x 100/ENV10
The bulk density (BD) of the soil needs to be taken into account when calculating the amount of lime needed to treat a given volume of soil.
The liming rate calculation for volumes of soil in cubic metres is shown below.
• Lime needed (kg CaCO3/m3 soil) = bulk density soil (tonne/m3 ) x net acidity (S% x 30.59) x 1.028 x safety factor9 x 100/ENV10

https://www.der.wa.gov.au/images/do...t_of_soil_and_water_in_acid_ss_landscapes.pdf

Lime is not a cheap option if you add the labour, machinery and testing costs to the lime cost. Furthermore they cannot work 24/7 and in all weather conditions