Treatment Train: Excavation, Dewatering and Water Treatment, Chemical Dosing, Air Sparge and Soil Vapour Extraction

Mildenhall

Background

Ahead of a proposed site redevelopment which included the demolition of an existing petrol filling station, private dwelling and MOT garage, RemTech was appointed to assess and resolve subsurface contamination before development work.

RemTech Role

RemTech was responsible for reducing known petrol contamination in soil and groundwater to agreed, target concentrations in order to allow re-development for continued commercial use. Its work included the following:

  • Identifying and exposing all old tanks, lines and other petrol station infrastructure. Emptying and de-gassing infrastructure.
  • Breaking out the concrete cover and cradles then removing the tanks so they can be cold cut and disposed of.
  • Removing contaminated water and any liquid fuel from the excavation areas and treating the water to remove dissolved contamination prior to disposal under permit.
  • Excavating contaminated soils and then treatment of any residual exposed contaminated soils with chemical oxidiser.
  • Reinstate the area with clean imported structural aggregate compacted in 250mm layers.
  • Pilot testing of chosen remediation technology.
  • Installation of buried pipework to allow air sparge and soil vapour extraction.
  • Construction of a bespoke air sparge and soil vapour extraction unit for operation at the site during redevelopment work.
  • Monitoring, maintenance and optimisation of in-situ treatment to maximise efficiency and minimise remediation timescales.

 

Project Summary

Client:
Environmental Protection Strategies Ltd

Project Duration and Cost:
18 months – £100,000

Key Services:

  • Safety controls
  • Regulator, main contractor and client liaison
  • Waste characterisation and classification
  • Service avoidance
  • Excavation and dewatering
  • Effluent treatment
  • In-situ chemical oxidisation
  • In-situ soil vapour extraction and air sparging
  • Remediation monitoring, maintenance and optimisation
  • Decommissioning and removal of remediation equipment

Outcome:
The works were carried safely with no incidents or accidents. The project programme was met, planning conditions satisfied, and the site was handed over for redevelopment. The property now comprises a busy retail park including new petrol station, fast food outlet, car park and retail area.