Brownfield Briefing 2018 Award for the Four Ashes Project

The 32 hectare Four Ashes site was predominantly used as a chemical manufacturing works from the 1960’s up until it was closed and demolished in 2007. Following demolition, investigations identified large areas of the site were heavily impacted with a range of contaminants including, phenol, petroleum hydrocarbons, chlorinated solvents, BTEX and asbestos.

Remediation works were required to run concurrently with the construction of a 545,000 ft2 production facility for the international parts manufacturer Gestamp. The design included 7m deep press pits, requiring deep excavation in heavily contaminated soils and the associated water management.

Remediation Scheme

The initial remediation design was not feasible due to development constraints, so QDS worked closely with Hydrock Consultants to re-design the works. An innovative multi-technology remediation scheme was proposed, which included the onsite ex-situ bioremediation of 23,000 m3 of shallow soils, in-situ chemical oxidation of 15,000 m3 of soils, the processing and re-use of 2,000 m3 of soils impacted with fibrous asbestos and the onsite treatment of over 44,000 m3 of contaminated water. As a result, we secured rapid regulatory approval for a combined technology approach that could achieve the site clean-up required within limited space and programme.

The remediation scheme was very successful with over 115,000 kg of contaminated mass being destroyed, greater than 90% reduction of contaminant concentrations within the aquifer, allowing more than 99% of materials to be re-used as part of the redevelopment works.

What made FLI-QDS stand out from the rest?

We feel that one of the key elements resulting in the successful delivery of this project was the positive collaboration between all stakeholders working towards the same end goal. It was a very challenging site, due to both the heavy contamination and groundwater at surface level creating difficult working conditions.

Due to our in-house technical ability (including laboratory facilities) we were able to critically appraise the initial proposed remediation design in the context of the proposed development, in doing so we identified a number of elements which would negatively impact the proposed construction works. Working collaboratively alongside Hydrock Consultants and the client we were able to not only redesign the remediation scheme to address the impacts but also significantly reduced the overall programme and provided a significant cost saving.

What makes us proud of this project?

A new in-situ chemical mixing method was developed and bench tested specifically for this job. We were very pleased to see the new method exceed design requirements and achieve a >90% reduction in contaminant concentrations within a highly impacted aquifer.

Also, in what must be some kind of record, we received Environment Agency approval of the works completion within 24 hours of submitting the validation report. This was largely due to good regulatory communication which clearly demonstrated how an effective, sustainable and well executed project can showcase development driving the clean-up of our industrial past.

QDS’ flexible approach was key to this success, in particular how we took on problems that came to light during the redevelopment including major changes to the cut and fill design, site wide water management, remediation of asbestos impacted soils and buried waste drums