The site occupied a total plan area of 0.4 hectares and was situated approximately 1 Km south of Uxbridge town centre. Historically, the site functioned as a car dealership, vehicle maintenance and MOT companies, a welding shop and a tyre fitter from which various contamination issues had arisen.
Site Investigations revealed a ‘hotspot’ of contaminated soil towards the centre of the site with elevated concentrations of Polycyclic Aromatic Hydrocarbons (PAH). Groundwater was found to be contaminated with elevated levels of diesel range hydrocarbons.
The overall remediation strategy was designed to address the source and pathway contamination issues, as a measure to protect both human health and groundwater receptors. Envirotreat were awarded the Contract based on the flexibility of the E-Clay Technology and its application for the treatment of both the contamination hot-spot and groundwater migrating off-site, and the ability to offer the client a cost-effective solution.
The remedial operation involved the ex-situ treatment of the identified contamination hot-spot using the Envirotreat E-Clay Technology. The strategy also included the installation of an Envirotreat Soil Mixed Reactive Barrier System (SMRBS), comprising both passive and active sections. The objective was to treat contaminated groundwater as it migrated off-site towards the adjacent Fray’s River, utilising proprietary E-Clays.
The ex-situ treatment of contaminated soil enabled compliance with the identified Site Specific Target Levels (SSTL) through the immobilisation of leachable pollutants within the soils.
The SMRBS installation and ex-situ remediation operation were carried out on site consecutively using Envirotreats Mobile Treatment Licence. Specialist technology, materials and supervision were supplied by Envirotreat whilst subcontractors supplied all the required plant for the ex-situ operation and labour for application of the Envirotreat Process.
Methodology – Remediation Phase 1 – Ex-situ Treatment
The identified areas of contamination were excavated, stockpiled and treated on-site using the Envirotreat E-clay Technology. The ex-situ operation was carried out over a 2 week period, treating a total volume of 1,060m³.
The soils were mixed in batches with the E-Clay slurry until a homogenous mix was produced. The treated soils were then temporarily stockpiled before being reused on-site as a substitute for imported clean fill, thus preventing the need for off site disposal.