Soil and groundwater have been contaminated with volatile aromatic hydrocarbons and mineral oil at the Sappe- meer gas-production site. The extent and degree of contamination were determined in an extensive site investigation.

The clean-up operation has been designed so that normal plant operation can continue during the clean-up period. A combination of three techniques has therefore been selected: excavation of heavily polluted soil; vacuumex- traction of the heavily polluted unsaturated zone; and groundwater abstraction in the shallow and deep aquifer at a rate of 500,000 m3/year.

The design for the clean-up operation was finalized on the basis of test results from two pilot projects: a pumping test for groundwater abstraction and a vacuum test for vacuum extraction.

The initial results of the operation, which started in October 1990, are very satisfactory. Removal of 1 kg of contaminants costs USS 300. Clearly prevention and active monitoring of soil contamination will always be cheaper than an "end of pipe solution", such as a soil clean-up operation.

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