1. Built on an industrial waste land Stade de France H. Gregory & C. Denis

2. Introduction 1912-1966 (54 years) Cornillon gas factory Produced gas for heating and lighting 1 ton of coal Waste stocked on site 60kg of tar 150l of ammoniacal water

3. Soil composition: Geological bassin of sedimentary rocks Successive marine deposits More than 50 000m³ must be treated Impossible for economical reasons : too much soil First idea: incineration Background

4. 3 types of contaminated soil 1st: pitch, tar, bitumen and soil containing polycyclic aromatic hydrocarbons (PAH’s) PAH’s concentration > 50,000 ppm (ppm= parts per millions=1 milligram per kilogram of soil (mg/kg) ) Solution: incineration 2 nd : soil with PAH’s concentration, c: 500ppm<c<50,000ppm Solution: Biological treatment in situ: biological mound Rocks which cannot be cleaned up that way were washed with special machinery 3rd: soil with PAH’s concentration, c: 30ppm<c<500ppm Not dangerous to health or stadium construction left in place but laid out in layers separated from the surface and the water table Soil with hydrocarbons concentration < 30 ppm are considered inert

5. Possible solutions Biological methods : Bio-remediation Aeration – inject air into / puncture the soil, enabling a phase transfer of hydrocarbons from dissolved to a vapour phase Physical methods: Soil washing Incineration Soil vapour extraction systems - PVC pipes are used to collect gases Barrier – a vinyl sheet protects upper layer (including playing field) Solidifaction / Stabilisation - Excavated and cement / bitumen added in a cold stabilisation plant.

6. Bioremediation 530,000 cubic feet of earth cleaned in this way. Soil moved into a biological mound Decontaminated by adding micro-organisms and nutrients into the soil Activates the naturally occurring microbes in the soil, degrading the contaminants. Reduces the degradation time to a few months (usually take 100’s of years)

7. Soil washing Inexpensive Soil washing separates soil by particle size. Most organic and inorganic contaminants tend to bind and sorb to clay, silt, and organic soil particles. Most silt and clay sticks to larger particles like sand and gravel. Surfactants or similar mild solvents helps remove petroleum hydrocarbons and other organic contaminants. The separated material is smaller in volume and is more easily disposed of or further treated.

8. Conclusions The contamination was actually cleared rather than prevented from travelling further with a barrier Maintenance and inspection not necessary Very expensive Time consuming (2 years) It was successful!