Question

what is the spoil quality of air

Answer 1

It is very high!
A number of procedures have been developed to control dust emissions and include: 

Watering of active mining areas, active spoil emplacement areas and haul roads that are subject to frequent vehicle movements;All drill rigs are equipped with dust control systems and are regularly maintained for effective use;Automatic sprays fitted to the dump hopper and crushing plant to minimise dust from coal processing activities;