THE CHALLENGE:
Targeted remediation followed by bulk excavation of soils was required to initially install Secant Pile Platforms at reduced levels across the development footprint, followed by bulk excavation of a large basement footprint. Due to the former site use, substantial in-ground obstructions were present and large volumes of surplus contaminated soils required removal. Continual collaboration with key project stakeholders was necessary to ensure project sustainability goals and remedial objectives could be met, on a busy, logistically constrained multi-phase construction site for a client with exemplar HSQ&E standards.
OUR SOLUTION:
Soilfix implemented a Remediation & Enabling works programme that included:
- Targeted source remediation including a backfilled former Tar Tank, Purifiers, Toluene Tank plus redundant tar & liquor pipework;
- Bulk excavation of materials and breakout/removal of substantial gasworks infrastructure (including gasholder walls & large gas mains) – 90,000m3 excavation & breakout carried out in two stages (Dig 1 & Dig 2 levels) to progressively enable deep basement construction;
- Management / pre-treatment of arisings on-site to recover aggregates for use in the pile mat construction and to minimise soils sent to landfill;
- Approximately 79,000m3 material disposed from site in accordance with full Duty of Care;
- Approximately 11,000m3 of aggregates re-used to form multi-level pile platforms;
- Remediation of a 15m diameter 6m deep former Tar Tank with comprehensive odour suppression;
- Periodic UXO Engineer supervision and In-situ Mag-cone probing for UXO clearance;
- Installation of sheet piles using vibrationless techniques for temporary retainment, adjacent to a Grade II listed Gasholder – the world’s oldest structure of its kind;
- Attendance of piling works with further management and disposal of arisings;
- Groundwater management & NAPL recovery to facilitate deep excavations through an on-site water treatment plant – including pH correction air stripping for ammonia treatment;
- Comprehensive environmental monitoring & controls, with particular focus on odour/VOC emissions and vibration due to sensitive adjacent receptors; and,
- Implementation of sustainability measures including use of HVO fuel in all plant.
Soilfix successfully delivered all works within the required programme, with zero . Effective management of soils & hardcore during all works enabled >95% of materials sent for off-site recovery rather than landfill, achieving >60% reduction in CO2e emissions from predicted.
