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 th e 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 diamete r than at the upper part of the sleeve so as to allow the flange to move horizontal ly with the liner relative to the member,
