HEAVY-METAL POLLUTION RELATED TO THE INFILTRATION OF RUN-OFF WATER INA PERVIOUS ROAD CONSTRUCTION

The fate of Pb, Cu, Cd, Zn and Ni, has been studied in a work located within a car-park associating a porous asphalt and a retention reservo ir, and allowing the on-site infiltration of stormwater in the soil. T he suspended matters from run-off water contain a large amount of Pb, Cu, Cd and Zn. The metallic pollutions are located in the porous aspha lt and close to the infiltration pipes which distribute stormwater in the reservoir. No pollutant effects could be seen in the soil under th e work. The porous road construction seems to filter the heavy metals contaminated suspended matter. The risk of heavy metals release from t he structure has been studied. During normal conditions of use, the po rous asphalt accumulates contaminated particles and, even with deicing salts, run-off water could only release small amounts of toxic metals . In presence of exchangeable ions, complexing agent or moreover acid solution, heavy metals could be easily mobilised from the construction . In order to limit pollution risks it seems to be necessary to clean the porous asphalt and to intercept suspended matters before their ent ry into the infiltration pipes.