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Biggin Hill

10 March 2017

Taylor Wimpey South Thames appointed Cognition to carry out remediation and earth works at a former RAF married quarters in Biggin Hill, Kent. 

Permission was obtained to build 18 low rise housing units with associated car parking and soft landscaping/domestic gardens. Out of the 18 homes, 8 affordable homes are proposed for the development.  

The site was idenfied in previous ground investigations to have shallow made ground present containing elevated levels of lead and PAH, with the presence of low-quantities of free-fibre and cemented asbestos.

Prior to the main works commencing, Cognition carried out tree protection works, surveys of exisiting utilities located within the site boundary and removal of unprotected trees and vegetation.

The main works comprised; non-notifiable, non-licenced hand picking of ACMs present within shallow made ground and removal of asbestos sheets located in a section of the site, by Cognition’s trained, non-licenced asbestos removal works operatives (NLARW).

Hardstanding areas, building sub-bases and underground obstructions from previous developments where still present, these needed removing as to not obstruct the future development. The obstructions were machine excavated and broken out.

Materials present on the surface of the site and within the made ground, which comprised timber, ceramics, metal, plastic and concrete were screened out of soils and disposed under duty of care.

Lead and PAH impacted soils were targeted on the site within the shallow made ground. Materials were stabilised and placed within roads.  Validation testing was undertaken of excavated hotspot areas.

The works were concluded with; finishing site levels and the construction of a fully engineered pile mat and road, using stabilised material that had undergone geotechnical testing to ensure suitability for intended use.

Landscaped and garden areas are to be capped with clean imported materials post construction works on the site (undertaken by a third party).


Stabilised pile mat Creation of the road sub-base, ready for stabilisation
small transparent gif for site construction purposes