Abstract: The floor under a chemical dump site is formed from a plurality of floor elements sealed with respect to each other by grouting material. Each floor element includes a male rib on one side and a female groove on the other side. The male rib has a dovetail geometry which is complementary to the geometry of the female groove. The male and female parts are adapted to mate and lock when the male rib slides longitudinally into the female groove thereby locking adjacent floor members to each other. The floor members are driven one behind the other in a string under the dump site. The male rib of one string engages the female groove of the next adjacent string until a floor of interlocking element strings is formed. Each floor member includes a hollow central channel running from end to end and a plurality of smaller apertures communicating the central channel with the vicinity of the male/female connection.