Project: Former Goods Yard, Dundee
Timescale: 6 months
Once described as "the most contaminated site in Scotland", this former rail goods yard had been used for engine servicing in the early days of rail and was affected by large volumes of engine oil, other NAPL and by-products of combustion such as benzo(a)pyrene (BaP). The site was also heavily affected by PCB’s.
As the PCB’s were partitioned into the oils it was decided that excavation delineation could be based upon visual and olfactory inspection along with site test kits provided and used by ERS staff for TPH.
Soil was initially excavated and screened. Soils that exceeded the site specific target level were bagged and craned onto articulated lorries for haulage to the nearest incinerator for final disposal.
Bioremediation of treatable soils was undertaken on an impermeable treatment area constructed by ERS. Excavation voids were pumped dry prior to backfill. This was undertaken using a peristaltic pump to skim NAPL from the surface first, whilst minimising suspended solids. All water was passed through ERS’ oil water separator prior to discharge to ground in a different area of the site under the terms of a discharge agreement with SEPA. Although this site was approximately 100 metres from the Firth of Tay the highly permeable nature of some of the made ground in the area meant that the site had a tidal influence on groundwater in some areas. This necessitated the introduction of additional pumping, water storage and treatment facilities to ensure that the project was completed on time.
Approximately 5,000 cubic metres of soil with an average starting concentration of 6,000mg/kg was treated to achieve a target criteria of less than 1,000mg/kg Total Petroleum Hydrocarbons.