Project: Former TXU Energy Site, Chelmsford
Client: Major House Builder
Contract Value: £500,000

Knight Environmental Limited provided our client with both environmental consultancy and remediation contracting services, to take the site from brownfield to a residential end-use.
The site was a former gravel pit which had been infilled with waste up to a depth of 6 metres covering approximately 50% of the 3 hectare site. It had then been developed as an engineering works and depot.

Knight Environmental Limited undertook desk-based research of the site, designed and conducted the site investigation, carried out the qualitative and quantitative risk assessments, prepared an outline remediation strategy and liaised with the Regulatory Authorities to gain approval of the proposed remedial design. Knight Environmental Limited was the principal contractor during the clearance, demolition and remediation of the site which also included the removal of notifiable asbestos.

Our sister company J L Knight Roadworks Limited were contracted to undertake the groundwork and construction of the infrastructure. This enabled a closely coordinated operation enabling remediation to run along side the development and construction works.

The site was identified to be contaminated with a myriad of contaminants residing in the Made Ground and the groundwater beneath the site including methane generating wastes, metals, petroleum hydrocarbons, polyaromatic hydrocarbons and volatile organic compounds.

The remediation developed for the site comprised the ex-situ remediation of 1,500 cubic metres of soil using patented e-Clay technology and specialist plant from Knight Environmental Limited. The sensitive garden and open space areas are being capped by the placement of a separation geotextile over the in-situ materials following the placement of a soil layer comprising of imported subsoil and topsoil. Gas protection measures are also being incorporated into the building design.

The groundwater beneath the site is currently being remediated using a series of ozone injection wells installed within the impacted area and linked to Knight Environmental Limited’s C-Sparge air sparging unit. The injected ozone assists the rapid degradation of organic compounds within the saturated zone.

The remediation work is being undertaken in a phased approach allowing the validation of the works to be an ongoing process in accordance with the requirements of the Local Authority Environmental Health Department and the Environment Agency thus facilitating a fast track approach to the development.