72.Residual hazardous materials may be stored in heaps outside a building only if
(1) 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.