Project: Remediation of a Domestic Oil Spill
Timescale: 3 months (including landscaping)
Following a fire, approx. 1000 litres of heating oil were lost in the rear garden of a domestic property and migrated across the garden towards the house. An initial site investigation to determine risk to property and human health had been carried out by another contractor, which recommended off-site disposal of impacted soils.
When ERS arrived on site to carry out the remediation works, a hydrocarbon odour was present in the rear garden, but no free phase kerosene was observed. Luckily, there appeared to be no damage to the building either. ERS proposed a further phase of investigation with a PID, to refine and delineate the soils which should be removed, which was accepted by the client.
To address data gaps and delineate the area of soil affected by the spill, ERS deployed high resolution site characterisation at the property, employing a high density of sample points supported by use of PID as a diagnostic tool to delineate the extent of the spill. Strong hydrocarbon odours and associated elevated PID readings were noted, primarily within the topsoil horizon, with the highest hydrocarbon concentrations closest to the oil tank – consistent with a leak migrating across the garden. From these findings and the results of the initial investigation, the extent of the remediation area was determined.
Under the direction of an ERS remediation site supervisor, soil within the remediation area was removed down to the base of the topsoil horizon – approximately a depth of 0.8-1.0m. Soils closest to the tank which had the highest hydrocarbon concentrations (up to 8,380 mg/kg) were excavated first and segregated for separate disposal. The excavation was then progressed across the remainder of the remediation area. The contaminated material was excavated and transferred to skips before being removed from site for off-site disposal at suitably licensed facilities.
Upon completion of the excavation, there was no olfactory evidence of contamination. Validation soil samples were collected and came back below the laboratory limits of detection for all determinants, confirming that all impacted material had been removed.
The excavation was then backfilled with clean imported material. Some additional cosmetic restorations works were also carried out for the home owner’s convenience, including replacing fencing and planting turf in the rear garden, and replacing the gravel in the driveway to the side of the property, which had been used for access and skip placement during the works.