The site is bounded by the River Avon and significantly contaminated with heavy metals, hydrocarbons and asbestos.
This project presented three major challenges. A reduced level cut involving approximately 5000m3 soil followed by construction of a large piling mat was necessary to achieve development formation levels. Secondly, off-site disposal volumes needed to be minimal to maintain project feasibility. Finally, with the River Avon immediately adjacent to the site, the overall strategy needed to limit mobilisation of contaminants both during the construction phase as well as the completed phase. The site presented additional constraints due to the requirement to work around existing high-voltage electric cables, live pumped foul/storm sewers as well as Japanese Knotweed infested areas.
Soilfix designed and implemented a multi-disciplinary remediation scheme with an engineered development platform in accordance with a Materials Management Plan (MMP) developed fully in accordance with the CL:AIRE Code of Practice (CoP), including:
- Development of a detailed conceptual model that considered both human health and groundwater flux to the River Avon. This was agreed with both the Environment Agency and local authority contaminated land officer;
- Treatment of Japanese Knotweed infestations along the Riverbank;
- Breakout, segregation and removal of slabs, substructures and sub base. Winning maximum recycled aggregate into Type 1 & 6F2 gradings for pile mats and pipe bedding was critical to the successful delivery of the development;
- Construction of cement stabilised working platforms and anti-vibration trench to protect HV cables prior to construction. Stabilisation enabled retention of contaminated soils whilst significantly reducing leachate and infiltration potential;
- Verification testing, reporting and regulatory signoff; and,
- Health, Safety & Environmental controls to meet Crest Nicholson’s stringent requirements.
Soilfix personnel were awarded a ‘Green Card’ for exemplary standards achieved. All works were successfully completed to enable commencement of piling on-programme with site specific geotechnical requirements met and no measurable impact to the river recorded during development.
Since completion, Soilfix has been endorsed by the Environment Agency Officer dealing with the project as a best-practice example of sustainable risk-based materials management in accordance with CL:AIRE Code of Practice.
