THE CHALLENGE:
Our client, Hill Partnerships were developing the 3.75Ha former Somerfields Storage & Distribution to a mixed residential scheme (including affordable housing) on behalf of Clarion Group. During the course of demolition works, significant contamination by asbestos cement sheeting (ACS) fragments and fuel oil was identified below the main warehouse and yard areas respectively. Areas of previously treated Giant Hogweed and extensive archaeological recording requirements also provided further logistical challenges for construction.
Initial estimates for remediation provided by third parties were in the range £4 to 12 million – rendering the entire development commercially non-viable. Soilfix were called upon to carry out a supplementary trial pitting exercise, hydrocarbon source area delineation and a controlled-waters DQRA in conjunction with Hill’s retained geo-environmental consultant, Merebrook Consulting, to provide a more sustainable and cost effective remediation solution.
OUR SOLUTION:
After carrying out supplementary site investigation and agreeing a Detailed Remediation Strategy with the Regulators, Soilfix designed & implemented a sustainable, cost effective solution, all fully in accordance with CL:AIRE Code of Practice (CoP), including:
- Breakout of remaining concrete slabs & sub-structures under watching brief by a certified asbestos operative. Processing 9,000m3 hardcore to 6F2 specification for re-use;
- Excavation of 10nr large archaeological trenches through Made Ground under controlled conditions, followed by enabling full archaeological investigation across two-thirds of the site to record Romano-Britanic artefacts;
- Decommissioning of oil contaminated drainage network, targeted remediation and bio-remediation treatment of 3,000m3 hydrocarbon contaminated source areas;
- Extended proof-digging below proposed drainage corridors & housing plots to remove impediments to construction;
- Cut & fill reprofiling of 12,000m3 Made Ground Fill to required levels including basement;
- Modular processing of Made Ground soils containing visible ACS fragments;
- Excavation and on-site encapsulation of Hogweed impacted soils within a root barrier lined ‘cell’;
- Targeted excavation and removal of localised areas of peat deposits underlying main infrastructure corridors to mitigate potential future settlement issues;
- Development platform preparation with site-won crushed materials; and,
- Third party site verification and reporting to satisfy various project stakeholders.
The works have achieved >99% materials recovery out of 32,000m3 materials subjected to breakout & excavation, with a variety of innovative remediation approaches applied.
