Petrol Station, Croydon, Surrey
Investigation and Risk Assessment
At the time of the original investigations, the site comprised a disused car sales and maintenance garage. It was proposed to redevelop the site with residential apartments.
It was developed by the 1930's with offices and garage and operated as a fuel sales and maintenance garage until its demolition in 2003. Enquiries with the Local Authority suggested that there were potentially eleven underground tanks across the forecourt area in the north of the site.
The soils encountered generally comprised fill, overlying superficial clay and sand deposits to around 2m bgl. The superficial soils were found to be underlain by Terrace Gravels. London Clay was encountered from depths of 3.5 to 4.5m bgl, which was in turn underlain by dense gravel of the Blackheath Beds. Rapid groundwater seepages were noted in the terrace gravels. Standing water levels were generally in the range 1 to 2.5m bgl.
In summary, the soils were found to be contaminated with Heavy Metals, Poly Aromatic Hydrocarbons (PAHs), and Petroleum Hydrocarbons (TPH). Groundwater samples were found to be slightly contaminated with TPH.
Remediation Design and Validation
Soil and Groundwater was remediated in-situ by a combination of Air Sparging and Soil Vapour Extraction. The in-situ apparatus was installed prior to construction and treatment carried out throughout the redevelopment of the site. Treatment took approximately nine months, and was finished, and signed off by the regulators, in advance of the property completions.
 |
 |
