The sulphate content of the groundwater gives the best indication of the likely severity of
sulphate attack, particularly that resulting from soluble sulphates. Where the water samples
are taken from boreholes care should be taken to ensure that the sample is not diluted by
water added to assist the drilling. If possible the groundwater should be sampled after a long
period of dry weather. Groundwater flow across a sloping site through sulphate-bearing
ground results in the highest concentration on the downhill side of the site and the flow may
488 The durability of piled foundations
Figure 10.3Disintegration of concrete in bored and cast-in-place pile due to attack by sulphuric acid
leaking into fill from industrial processes.