Project

Intensive In-situ Chemical Oxidation of gross chlorobenzene (MCB) and dichlorobenzene (DCB) contamination using an innovative soil mixing delivery system.

Contaminant

Chorobenzene and dichlorobenzene

Challenges

Very high concentrations of MCB and DCB were encountered throughout the subsurface, which comprised a complex mix of sands, silts and clays. Phase separated product was observed in a number of locations. In total five hot-spots were defined. The total treatment volume of these ‘hot-spots’ was 46,200 m³.

A DQRA, completed by the third party Environmental Consultant, determined that a watercourse at the down-gradient site boundary was at risk and reductions in dissolved phase contamination were required. Targets (based on 1,2-DCB) ranged from 1.1 to 5.5 mg/l, depending on distance from the receptor. Baseline concentrations ranged from 1 to >100 mg/l.

Churngold Solution

The CFA continually mixed the soil concurrent to injection using a specially designed mixing head that allowed uniform distribution of oxidant into the subsurface. This significantly increased the efficiency of the process by maximising contact between the oxidisers and contamination.

The majority of all areas achieved remedial targets after only one round of injection. Areas where contamination exceeded 100 mg/l achieved on average a 80% reduction in concentration after only one round. The system has also been proven capable of remediating zones impacted with Phase Separated Product.

The whole treatment process of the 46,200m³ of impacted soils was undertaken in only 20 weeks with validation sign off from the Environment Agency achieved 3 months later.

This solution confirmed that NAPL containing low permeability soils can now be considered for treatment by chemical oxidation, whereas previously the risk would have pre-cluded consideration of this technique.