In 2020, Cognition teamed up with Climate Care to offset our total annual emissions and becoming Carbon Neutral for the first time. In the same year, the company committed to stay proactive, adopting and developing more sustainable remediation methodologies, selection of materials and energy sources we use, reducing the need for offset element of our emissions. Our long-term goal is to continue improving efficiency and minimise emissions from our routine site and office operations across the board.
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A zero carbon company
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A zero carbon company
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Greenwich, Enderby Wharf

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The client:Barratt Homes
Services:Demolition and tank removal, Contamination hotspot removal, bioremediation, water treatment, earthworks, soil stabilisation.

The Challenge:

Barratt Homes redeveloped the site with the construction of eight apartment blocks. Originally four of the blocks were to be located over a large basement to be used for car parking constructed within a secant pile wall. The north west area of the site was covered by a slab over an infilled dock. The site had a long history of industrial use dating back to the eighteenth century with whaling, sail making, fuel supply, foundry works, concrete works and submarine cable making. These left the soil and groundwater contaminated with petroleum hydrocarbons, heavy metals and asbestos. A remediation strategy was put in place to reduce potential risks presented to human health and future infrastructure and potential risks to controlled waters including the Kempton Park Gravel aquifer. The site presented a number of challenges; close proximity to the Thames, shallow perched groundwater, numerous underground obstructions including old piles and foundations, and underground fuel storage tanks. The slab covering the infilled dock required removal and dewatering with the silt having to be stabilised to enable backfill and stabilisation to form a piling mat for the new development. The key objective of the remediation strategy was to maximise re-use of made ground and reduce need for disposal and import in a very busy area of London.

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The Approach

Cognition was appointed Principal Contractor to carry out the works prior and develop a strategy for approval by the regulators. The key elements of these works included;

  • Breakout of slabs and excavation and removal of underground obstructions and old infrastructure including underground storage tanks;
  • Process arisings to remove oversize materials and waste items such as wood and metals;
  • Pump and treat groundwater from silts in former dock area to remove NAPL and facilitate excavation;
  • Bioremediate hydrocarbon contaminated silt to enable its re-use;
  • Soil stabilisation of dock silts using excavator mounted mixing buckets to encapsulate and reduce leachability of soil contaminants such as PAHs and heavy metals;
  • Soil stabilisation of backfill made ground to form piling mats and sub-base of new roads and hard-standings.

The Outcome

The works successfully delivered significant savings for the client in terms of reduced disposal and maximising re-use. Stabilisation also negated the need to import subgrade material for road construction and crushed concrete for piling mats.

 

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