Remediation of TPH contamination on Vale Road, Tonbridge
The Challenge
Geostream UK was contracted to carry out remediation and earthworks on this heavily TPH-contaminated site, in preparation for the construction of mixed commercial units.
Over the past century the site had housed a gasworks, tar distillery and bitumen refinery, leaving behind a highly complex set of contamination. The site had been derelict for almost 20 years before works began.
Specific challenges included:
- Extensive hydrocarbon-impacted soils
- A 3,500m2 Benzyne-impacted groundwater plume
- The site being within 100m of a water course and railway line
- Significant underground concrete obstructions.
Migration of contamination into the water course was the primary driver of remediation.
Our Solution
We turned over the entire site, removing large obstructions down to 2.5mbgl. All materials movements were carried out under a detailed Materials Management Plan (MMP), and tracked in real-time using our in-house 3D GPS-enabled plant.
Before works began, we discharged our own Environmental Permit, having obtained discharge consent.
Our team treated contaminated soil by bioremediation or Stabilisation/Modification (S/M), using cement and granulated blast furnace slag as binder – which has zero carbon footprint. We also picked over 2T of asbestos from soils.
Sumps were installed onsite, then Benzyne-impacted groundwater was treated using a pump and treat system. This was followed by a programme of In-Situ Chemical Oxidation (ISCO), which saw us inject our UK-exclusive substrate, OBC, into 120 points across the site.
We used our in-house mixing trailer to boost efficient during the injection process, ensuring accurate control of pressures, flow rates and volumes for each point injected.
Dust suppression, Benzyne monitoring and noise monitoring were conducted throughout works. The project was overseen by our dedicated health and safety team, ensuring high safety standards and that no incidents were recorded.
Our Results
- Soil and groundwater remediation on track to meet targets
- Works completed on time and on budget
- Processed 5,500m3 material into reusable 6F2
