Remediation of the polluted soils
Until 1992 a leading name in the French automotive industry – Renault had an operating factory in Boulogne-Billancourt, Paris area. Following the closure of this facility, it was a standard practice to carry out an environmental screening of the factory area. This investigation has shown presence of hydrocarbons seepage and chlorinated solvents in the underlying soils. Renault focused their efforts on successful remediation of the polluted soils and in 2007 decided to invite Sol Environment, a specialized soil remediation contractor, to propose its solution and carry out the works.
As a first step, it was necessary to carry out preparatory works consisting mainly of soil reinforcement along boundary wall separating it from the adjacent road. As part of this activity, retaining secant piles have been designed to enable the excavation of soils up a total depth of 8 m, with 4 m below ground water level.
Following the completion of the preparatory works, polluted material was selectively excavated, sealed and transferred to processing areas, where they were cleared prior to being used for backfilling. With the excavation works being carried out below the water table, it was necessary to proceed with hydrocarbons skimming. With the implemented in-situ system Sol Environment extracted and collected 250m3 of free hydrocarbons, which in large extent was re-used for energy production.
Biological treatment implemented by activation of the native fauna by providing oxygen and nutrients led to degradation of hydrocarbons adsorbed into the soil. 47,500 m3 of oil polluted soil has been treated in accordance with pollution control objectives determined by the local authorities.
1,500m3 of soil polluted by volatile organic compounds (mostly chlorinated solvents) was treated by mixing with ventilation.
The acceptance testing of the edges and bottom of the excavation and the excavated treated material involved taking about 2,500 samples with 101,500 parameters analyzed.