Abstract: A joint/sealing system for interlocked, in-ground barrier members which form an in-ground containment wall, including a "U" shaped gasket (108) interfacing with a longitudinally extended male member (109) to form oppositely directed, double seals using outwardly diverging lips (181/182, 183/184) on the distal ends of the gasket, with the seals being created between at least one side of the male member and at least one leg of two legs (107), which form a female cavity (110) for the male member. The joint includes two, flanking "T" shaped, longitudinal extensions on opposite sides of the male member mating with opposed "T" configured chambers (102') on the adjacent barrier member. The joint elements preferably form an "H" nested within two, opposed "J" shapes. Six exemplary embodiments are disclosed, some single wall and some double walled. The gasket lips typically emanate out from the ends of the "U" shape, but one embodiment (501) has the lips extending out from the sides of the "U" (FIG. 10 ).