1. MENDIOLA, Cecilia PRESCOTT, Daniel SAUTEL, Benjamin

2. Historical background The ballast pond behind the Moulin Blanc harbour in Brest was commissioned in the late seventies. It was used to store some of the waste from ships that cleaned their ballast tanks when berthed at the Port de Commerce quayside.

3. Historical background On March 16, 1978, the oil tanker Amoco Cadiz got caught in a storm off the coast of Brittany, France, at the southern end of the English Channel. The ballast pond in Brest, was used to store some of the waste from the Amoco Cadiz wreck.

4. Aerial view of site It was decided in the late nineties to shut down the pond and reclaim the land for development as an industrial building site.

5. Description of site Soil contained a large amount of hydrocarbons (more than 35%) spadeable or even semi-liquid. Trails of heavy metals Soil heterogeneous : presence of different layer of bad quality

6. Adopted solution: Active barrier and stabilization. A strip of soil was first treated with the mixer. Once this consolidated strip had set, it was used as a working platform to treat the second strip. The whole area of the pond was treated in strips in this manner. Stabilization: They used a machine to mix the soil and an injection system to introduce the material that stabilised the ground.

7. Adopted solution: Active barrier and stabilization.

8. When it becomes saturated with rain, excess water escapes through the filter gates and emerges free of any residual pollutants (from any minor leachate that is not fully controlled by the stabilisation work, and from any soil left untreated inside the barrier). Active barrier: It isolates the enclosed soil from the outside world.

9. Results ADVANTAGES: It forms a twin barrier, of material stabilised at microscopic scale and a macro-scale slurry wall around the site. Stabilisation reduces the leaching potential and the filter gates trap any residual leachate. If subsequent building work on the site breaks up the stabilised material in places, releasing contaminants, these are also trapped by the filter gates.

10. Conclusion The combination of these two systems, offers a new, economically attractive approach to the rehabilitation of ballast storage ponds. Measurements taken after the use of these systems comply with government regulations: - THC < 1 mg/l - Phenol < 0.1 mg/l - Heavy metals (Ba, As, Ni, Co, Cu, Pb) < 0.1 mg/l