Phase 3 - Remediation

Where the Phase 1 PRA, Phase 2 GQRA and/or DQRA identify unacceptable risks in the context of the current or proposed use of a site, then remedial measures would be required. The aim of all remediation techniques is to break the pollution linkage between source and receptor, for whcih there are a wide range of remedial methods available with the method chosen being dependent upon the contaminant(s) identified, the site conditions, the proposed development, timescales and budget available.

There are two parts to remediation:-

    (i) Options Appraisal
  • Identification of feasible remediation options (review and refinement of CSM, definition of remediation objectives, compile a shortliest of remediation options).
  • Detailed evaluation of remediation options (evaluation of options individually and in combination, proposal for which options is/are most appropriate).
  • Development of a remediation strategy (consideration of zoning and timing of remediation, how the strategy is to be verified, costs and benefits, practical strategy for remediation.
    (ii) Implementation
  • Preparation of an implementation plan (identifiaction of management responsibilities, consultation with relevant parties, confirmation of regulatory permits required, phasing and timetable).
  • Design, implementation and verification of remediation (pilot trials, procurement of contractors, permits, production of verification plan, implementation of remediation, verification reports).
  • Long-term monitoring and maintenance (monitoring of how succesful remediation strategy was and where necessary take corrective action).

There are a wide range of remeidation techniques available a range of which are briefly described below.

Physical remediation techniques include:-

  • Capping – Hard-standing or ‘Inert’ soil cover systems providing a barrier and/or reducing infiltration.
  • Removal – Excavation and disposal of contaminated hotspots to a suitable landfill or where possible an appropriately permitted waste recycling, treatment or recovery facility.
  • Vertical Barriers – Subsurface barriers to minimize movement of contaminants and/or groundwater.
  • Horizontal Barriers – Reduce downward movement of contaminants.
  • Capillary Break – Prevents upward movement of contaminants by capillary action.

Treatment technologies may also be employed to remediate contamination, which may include:-

  • Vapour Extraction – Vacuum pumps or fans are used to reduce vapour pressure in wells causing air and VOCs to flow out causing volatilization of contaminants.
  • Bioremediation – Introduction or stimulation of micro-organisms to break down organic contaminants.
  • Soil Washing – Water based technique for separation of contaminants from granular soils.
  • Solvent Extraction – Use of solvents to selectively remove contaminants from soil.
  • Pump and Treat – Water is pumped out of a contaminated zone, treated and recycled.
  • Thermal Treatment – Ranges from incineration to thermal desorption of volatile and semi-volatile contaminants.
  • Stabilization/Solidification – Fixing of contaminants in a resistant solid matrix i.e. Lime.

At TGEN our consultants have experience of selecting, designing and implementing a wide range of remediation programmes. Through continued dialogue with our clients and the regulatory authorities we ensure that the most appropriate, efficient and practical remedial measures are implemented to achieve the remediation goals of the project.

If you would like further information on remediation techniques, or would like to discuss a particular project then please contact us as info@terragenenvironmental.co.uk