8 REMEDIATION OPTIONS - Castings Technology International

8. Remediation Options
8.2 Pathway Interruption
Once contamination has been released into the ground it can migrate vertically and laterally
contaminating ever-larger volumes of ground. Once contamination reaches the water table, it may
float on top of groundwater, sink through it or either readily or sparingly dissolve in the groundwater.
Preventing the spread of contamination may be an interim solution until the source can be dealt with
or it may be sufficient to render land fit for its current or intended use without removing the source.
Under the PPC regime pathway interruption is unlikely to be acceptable to regulators as a permanent
solution but may be needed to prevent further spread of pollution.
8.2.1 Soil
Receptors can be protected from exposure to contaminants in soil by means of barriers between
source and receptor. Options include:
• capping layer thick enough to stop people coming into contact with contamination,
• vertical barrier keyed into an underlying low permeability soil.
8.2.2 Water (dissolved phase)
In situ remediation options include:
• biostimulation, where natural microbiological processes are accelerated by adding something
for ‘bugs’ to eat and/or to breathe.
• permeable reactive barriers,
• air sparging.
Ex situ methods of treating dissolved phase contaminants are based on conventional waste water and
effluent treatment and include:
• filtration,
• biostimulation,
• pH adjustment.
8.2.3 Vapour/ gas
The distinction between source and pathway for vapour or gas contamination is determined by
concentration and is therefore a blurred one. Vapours may also form part of the pathway by which
volatile liquid contaminants can reach people. In situ remediation options include:
• permeable reactive barriers,
• venting trenches,
• capping,
• vertical barriers,
• gas proof membranes beneath buildings,
• soil vapour extraction.
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