Ex-situ soil bioremediation with soil vapour extraction in Northamptonshire
Client: Housing developer
Contract period: 16 weeks
Our Client required an experienced bioremediation contractor to treat contaminated soil on their three hectare former industrial site which was being redeveloped for housing. Various phases of investigation undertaken by a leading environmetal consultant identified an area of ground contaminated with Volatile Organic Compounds (VOCs), predominantly Trichloroethene (TCE) and cis 1,2-Dichloroethene (cis 1,2-DCE). Contamination was confined to the made ground and shallow fissured clay, to a depth of around 4.0m.
The remediation strategy was excavation of the VOC contaminated soils, initial processing and then placement on an on-site treatment pad. Initial processing was required to break up the structure of the heavy clay material to make it workable, allow efficient aeration, and make it suitable for replacement and compaction following treatment. Treatment was by ex-situ soil vapour extraction and bioremediation.
Contaminated material was systematically excavated, chasing out VOC contamination as the excavation progressed. Contaminated soils were initially processed within the excavation area by mixing with granulated quick lime using a specialised soil mixer attached to a 20 tonne excavator. A treatment pad area of approximately 3,000m2 was constructed prior to the soil excavation works commencing. The treatment bed was actively aerated by inocorporating a vacuum aeration system connected to an air distribution pipe network to induce air movement through the treatment bed. Any VOCs present in the extracted air were collected by activated carbon adsorption.
Once the required remediation targets had been reached, the treated materials were transported back to the excavation void. Reinstatement was carried out in accordance with Series 600 Specification for Highway Works. Following submission of our technical validation report to the Local Authority, planning conditions relating to ground contamination issues were lifted allowing site re-development to proceed.
- Remediation options appraisal
- Development of appropriate remediation strategy
- Soil excavation and pre-treatment
- Preparation of treatment area
- Construct treatment bed with active aeration system
- Optimisation of treatment, monitoring and sampling
- Reinstatement excavation with treated soil
- Compilation of validation report
A very cost effective solution was provided, allowing planning conditions to be discharged and the development to be completed.