Origin of the incident

Historical pollution. Leak in a set of diesel storage tanks protected by a concrete holding tank containing all storage tanks.

Pollution description

On a surface equivalent to a football field, a free phase of diesel, a few centimeters to tens of centimeters thick, located under and outside the holding tank, on the side of the aquifer discharge.

Geography and nature of the terrain

  • Along a sea access canal, with small level variations in the canal
  • Sand

Variability of the groundwater

  • Average depth of aquifer 2.3 m below ground level
  • Seasonal variability of aquifer between 50 and 70 cm per year depending on the considered wells

Solution implemented

  • 20 wells, diam. 600 mm, depth 4.5 m, used for drawdown and filled with a gravel pack consist-ing of 4/8 mm gravel, equipped with a 110 mm slotted liner. 10 wells are used in parallel of the drawdown for hydrocarbon skimming.
  • A continuous trench with a 600 mm width, a depth of 4.5 m, and a length of 90 m located between the storage area protected by the integrated holding tank and the neighbouring plots. This trench is intended to create a barrier to recover the product by lowering the water table. Average drawdown of +/-25 cm.
  • As a first step, installation of a pumping unit DS 500-12 and 12 skimmers SKIM 2-25, with a storage capacity of 0.8m3 of product. In a second step, modification of the pumping unit DS 500-12 by addition of a 2.5m3 product storage container to minimize the costs associated with the discharge of the pumped product.


Over a period of a little less than 2 years:

  • 10 m3 of pure product recovered
  • An average of 16.6 L/day of pure product pumped per day
  • It should be noted that the quantity of pumped product is doubled while draw-down is active.

Key Data


Nb of Wells
20 drawdown wells
10 wells

2.5 m

Pumping Unit
DS 500-12

SKIM 2-25

Ghent, Belgium

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