The Challenge
Comprehensive remediation of a free-phase hydrocarbon source area and deeper chlorinated solvent contamination was required to mitigate risks to controlled waters and future residents. Further challenges included the requirement to carry out archaeological investigation of remains relating to the neighbouring Barking Abbey prior to intrusive works and Flood Defence measures of the River Roding forming the western boundary of the site.
Our Solution
Soilfix implemented a remediation and development platform preparation scheme to the satisfaction of the clients environmental consultants, the Environment Agency and Local Authority, achieving >90% materials recovery. Works included:
- Controlled slab breakout and targeted obstructions removal (up to 4mbgl). Process/crushing hard materials for re-use as part of the working platform layer across building / external areas;
- Gross contamination within the hydrocarbon hotspot was identified and removed via excavation as much as practicable;
- Over 2,000m3 gross hydrocarbon contaminated soils underwent bioremediation treatment to reduce concentration of contaminants below site specific remedial targets;
- Surfactant-enhanced product recovery and residual smear zone treatment using sequential RegenOx PetroCleanze™ injection and pumping of the gross hydrocarbon impacted smear zone;
- Controlled release 3-D Microemulsion® (3DMe) substrate was injected into the saturated zones of the two chlorinated solvent source areas;
- To further manage the groundwater pluming a permeable reactive barrier (PRB) was installed and injected with 3DMe. A ‘top up’ injection visit will be undertaken via below-ground injection infrastructure post-occupation to ensure an effective barrier longevity >12 years;
- Stabilisation treatment of screened fines to provide a more sustainable and cost effective working platform solution across the site; and,
- Off-site disposal of surplus segregated, pre-treated materials as non-hazardous and inert waste.
Post-completion monitoring is currently underway for a period of up to 18 months. To date, no rebound of separate phase hydrocarbon has been detected and concentrations of chlorinated solvents have already fallen below the betterment targets agreed with the EA.
