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Guildford, Slyfield Regeneration

The client:Balfour Beatty
Services:Excavation, waste segregation and treatment, water treatment, dynamic compaction, stabilisation, deep drainage, road construction kurbs, beany blocks, surfacing, street lighting, civil engineering.

The Challenge:

The site was located on the periphery of an industrial estate and encompassed former sludge lagoons used by Guildford sewage treatment works. Gravel abstraction had been carried out on the site since the 1960s and was subsequently used as a waste site, having received a mixture of commercial, industrial and domestic waste from the 1980s. The contaminated landfill material and potential for Asbestos Containing Materials (ACMs) presented a human health risk during the construction works. Other materials on site presented geotechnical challenges such as the high organic content of the lagoon soil. Cognition was appointed to deliver Phase1 of Slyfield Area Regeneration Plan (SARP). The purpose of the first phase of remediation was to excavate, process and dynamically compact the site to form a geotechnically suitable platform for the construction of access roads to the proposed Clay Lane Link Road that will serve the wider development.

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The Approach

The key elements of these works included;

  • Identification of any visible, non-notifiable ACMs encountered in landfill material and disposal of these off-site;
  • Screening, processing and handpicking of ACM and deleterious waste;
  • Dust and odour suppression using mobile atomiser units;
  • Former sludge lagoon excavated and high organic-rich soil disposed off-site;
  • Construction of engineered embankment using segregated/site-won cohesive soils from the landfill area;
  • Dynamic compaction to geotechnical improve banks and subgrade for construction of roads; and
  • Installation of foul and surface water drainage
  • kerbing and permeable paving infrastructure.

The Outcome

Cognition successfully remediated the landfill and sludge lagoon, reinstating the gas membrane over the remnant fill. An engineered embankment was constructed through the lagoon area using site-won soils proposed by Cognition as value engineering to the client. This solution offered considerable cost savings whilst meeting the Client’s sustainability objectives. The design incorporated geogrid and erosion control measures. All roads were installed to highways standards as set out in the design manual for roads and bridges.

small transparent gif for site construction purposes