72. Residual hazardous materials may be stored in heaps outside a building only if1° the materials are in a solid state at 20 ºC;
2° the materials are not flammable or explosive and do not contain any volatile toxic substances;
3° the materials are stored in a site having a basin with a permeability coefficient of 1 × 10-6 cm/s able to withstand the effects of vehicular traffic. Unless the materials are covered with an impermeable membrane or are deposited in a site equipped with at least a roof and 3 sides, the basins shall be laid out in a way as to prevent the scattering of dust and to contain the monthly average quantity of precipitation received during the last 5 years in the region; and
4° the storage site is surrounded by a dike that prevents materials that are stored therein from contaminating surface water.