The six-acre site created in 1861, was once home to London's biggest factory, after its closure in 1979, it became derelict and was later selected to be one of East London's first urban renewal projects. Today, the site has become a focal point of the area's ongoing transformation.

The site is currently being redeveloped to create a large scale, mixed-use scheme with 1,000 residential apartments, retails units and a museum. However, previous attempts to regenerate the site have stalled due to extensive contamination, archaeological constraints and concerns over commercial viability.

To understand and address the site's issues and to realize its full development potential, Idom Merebrook was engaged to provide a robust, sustainable remedial solution, designed to preserve the site's heritage and ensure suitability for the new development of residential, leisure and retail outlets.

Rob Glavin, technical director, Idom Merebrook said: "It is hugely satisfying to know that we have been instrumental in developing a site that could otherwise have remained derelict for many more years. The site has huge potential but has been a challenge to make fit for purpose.

"Our understanding of the ground conditions, interpretation of the risks and how to manage them meant that we were able to offer a practical, deliverable solution to help realise the site's full development potential."

Following a comprehensive site investigation, the Idom Merebrook team took a pragmatic approach to address the multiple remediation challenges and worked closely with regulators and stakeholders to ensure the right strategic methodology.

The site posed some formidable challenges including; geotechnically poor ground conditions, significant hydrocarbon contamination, two deep chlorinated solvent hotspots and planning conditions dictated by a programme of archaeological works.

Additionally, the remediation work was to be located adjacent to the River Roding's flood defence measures (sheet piled wall with tie anchors) so works were designed to ensure river defences were not compromised.

A combination of innovative techniques was applied. Firstly, a combination of trial pits and magnacone surveys were used to identify the location of the tie-anchors. It was found that they did not extend into the contamination source areas, and the information gained through this technique has been used to inform a more cost-effective design and has become the foundation solution for the proposed development.

In conjunction with this, further site investigation was undertaken to delineate the areas of contamination. The site investigation included drilling groundwater-monitoring boreholes to the full depth of the river terrace gravels, supplemented by shallower windowless sampled probe holes.

The deeper boreholes were important in the process to enable the establishment of a potential DNAPL source moving across the surface of the London clay.

The site investigation data effectively delineated the source areas and identified the potential migration pathways. Following consultation with the Environment Agency and local authority environmental health officer, a scheme was designed to achieve the following:

• Hydrocarbons: free product removal from waters and excavation/treatment of grossly impacted soils, with injection/mixing of a mild chemical oxidant to promote enhanced flushing of free product and residual saturation. The objective was to achieve no measurable free product in groundwater and leachable TPH concentrations below solubility limits.
• Chlorinated solvents: injection of controlled release substrates to cause contaminant breakdown through enhanced reductive de-chlorinating processes.
• Provision of a 150m long in-ground permeable reactive barrier around two sides of the development. The purpose of the in-ground barrier is twofold, firstly to prevent the migration of residual contamination off-site, but also to prevent contamination rebound from offsite contamination.

The final development would also be provided with development-related measures such as clean cover in areas of soft landscaping, upgraded water pipes and vapour membranes as appropriate.

In adopting this approach to remediation, the team was able to provide a cost-effective, measurable and deliverable solution to enable the redevelopment of the site. This will form part of Barking's vibrant new community and contribute to the area's ongoing transformation.

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