Project

Remediation of a Former Industrial Site to allow sale of the land for housing redevelopment.

Contaminant

Xylene impacted soil and groundwater, chlorinated solvent impacted groundwater, asbestos impacted Made Ground and lead contaminated soils.

Challenges

The main challenge was a low permeability silt layer heavily impacted with Xylene, which was sandwiched between two permeable strata. This made the in-situ clean-up of the silt very difficult and prolonged using conventional vacuum technology.

The site was also impacted with a chlorinated solvent impacted groundwater plume and had hazardous levels of near surface lead contaminated soils. In addition asbestos was encountered during the project interspersed within a backfilled demolition type rubble. As such a number of different processes were required to achieve the project targets.

Churngold Solution

The solution comprised the injection of high pressure steam to mobilise the volatile contamination within the silt layer. The system significantly raised temperatures in the subsurface resulting in Xylene rapidly desorbing from the silts and being recovered as vapour or in the dissolved phase using a high vacuum extraction system. Subsequent air injection also induced hydrous pyrolysis that further destroyed the contaminants.

The chlorinated solvent plume was treated by injection of HRC that induced reductive dechlorination and that achieved target concentrations. The asbestos was hand picked out of the impacted soils under strict Health and Safety protocols and significantly reduced the volume of hazardous material to landfill. Due to the near surface nature and the proposed redevelopment of the site the hazardous lead contamination was disposed of to landfill.

Technologies employed

• Steam Injection
• High Vacuum Extraction
• Hydrous Pyrolysis
• Reductive dechlorination (HRC)
• Disposal to landfill
• Complex segregation
• Earthworks re-profiling