Abstract: In secondary containment of a liquid in a tank which has pipes or posts extending into the ground, a liner covering the ground within a containment wall has a hole surrounding each pipe. Each hole is sealed by a boot which surrounds the pipe and connects from the pipe to the liner and includes a sleeve portion clamped to the pipe and a flange surrounding the sleeve portion at one end which is welded to the liner. A frusto-conical or accordion shape expandable portion is provided allowing longitudinal movement of the flange relative to an upper part of the sleeve of the boot such that the expandable portion allows the liner lies to move downwardly relative to the pipe. The expandable portion is of larger diameter than at the upper part of the sleeve so as to allow the flange to move horizontally with the liner relative to the member.