The Royal Wharf development is located in Silvertown on the northern bank of the River Thames

The 15 ha site was part of an industrial estate split into Minoco Wharf, Crescent Wharf and Venesta Wharf. The site and surrounding area have had a varied industrial history including a chemical works, oil depot, colour works and TNT factory.

CGL conducted a data review of previous investigations at the site and subsequently scoped and supervised an extensive series of intrusive investigations including 31 cable percussive boreholes, 157 window sampler boreholes and 30 trial pits. Nine ground gas and groundwater monitoring visits were also undertaken from 87 monitoring installations.

Our investigations identified contamination in the soil and groundwater that posed a risk to human health and controlled waters, including heavy metals, hydrocarbons, asbestos and dye waste from past industrial works on the site and the surrounding area. Elevated ground gas concentrations were also encountered.

As a result of the findings we completed a detailed quantitative risk assessment (DQRA) to quantify the risk to the underlying Chalk aquifer and nearby River Thames. We also prepared a piling works risk assessment to assess whether the proposed piling methodology would result in a pathway to the underlying aquifer.

Based on the risk assessment and in liaison with the Environment Agency and local Environmental Health Officer, we prepared a remediation strategy for the development. We have also provided waste management support for the project and have undertaken investigations as part of the river wall replacement works along the southern boundary of Minoco Wharf.

The scope of the remediation works was integrated with the concurrent construction works including extensive basement works and re-levelling of the site to enable the proposed luxury ‘village’ style redevelopment.

The remediation works included:

• Hotspot removal with localised groundwater pump and treat.
• Installation of a reactive clay barrier wall to prevent off-site migration of shallow groundwater contamination.
• Gas protection of buildings without ventilated basements, including re-assessment of gas venting based on observed ground conditions.
• Soil stabilisation by cement to create re-usable engineering fill (under a CL:AIRE Code of Practice protocol).
• Removal of buried tanks where encountered.

As the works have progressed through four stages of the development, CGL has provided technical support on the remediation details, liaised closely with the Project Manager, remediation contractor and main works contractor, and undertaken observation of remediation works to provide a third party verification of the works. CGL has also provided Verification Reports as evidence of the works completed, including deviations from the strategy agreed with the Local Authority.