Cedar Meadows, Woolmer Green, Knebworth

Cedar Meadows, Woolmer Green & Knebworth Project Overview

 Taylor Wimpey instructed Soiltechnics to undertake a ground investigation for residential development between Cedar Meadows, Knebworth and Woolmer Green.

The site was partially occupied by an existing warehouse (formerly a milk factory and chemical works). They planned to demolish the warehouse, replacing this with residential houses and apartment blocks with private and communal gardens.

The eastern half of the site was densely populated with mature oak, willow and hawthorn trees, which required removal to allow the proposed development to take place.

Scope of Works

Soiltechnics undertook a ground investigation to assess the geological profile of the site. The investigation comprised sixteen windowless sample boreholes and three cable percussive boreholes.

Cedar Meadows, Knebworth and Woolmer Green is situated immediately east of a railway line. The industrial processes and underground storage tanks on-site presented a contamination risk. Accordingly, we took samples to assess the risks of chemical contamination.

The mature trees and near-surface cohesive deposits created a potential risk of severe desiccation. Therefore we took samples for subsequent laboratory testing to assess the degree of desiccation.

Finally, we prepared a single report summarising our interpretation of the ground investigation and laboratory testing. The report highlighted key ground-related risks and presented possible mitigation options.

Value Added

Soiltechnics carried out a desiccation survey to assess the risks of desiccation. The survey concluded that desiccation occurred to depths of 2.0-2.8mbgl. Therefore, potential heave following rehydration of cohesive soils would require consideration.

Our assessment of chemical contamination identified local hydrocarbon contamination, bulk asbestos fragments and elevated concentrations of commonly occurring contaminants. A remedial strategy including local removal of TPH hotspots and capping of proposed soft landscaping was produced. This limited the volume of material requiring export and thereby minimised cost to the Client.