Abstract: A secondary containment system (1) for installing around a ground-based primary vessel (6), the secondary containment system comprising a bund (2) having a base panel (3) and an endless wall (4) defining an enclosure. The bund (2) is made from several prefabricated sections (2a, 2b, 2c, 2d), each pre-fabricated section being itself made from one of more component parts (31-34, 41-48). When the pre-fabricated sections are assembled around the primary vessel a central opening (3b) is defined in the base panel (3), whereby inner edges (30) of the base panel (3) which define the central opening (3b) surround the primary vessel (6). The inner edges (30) are hermetically fastened to a substrate surface (50) on which the primary vessel (6) and the bund (2) are installed to form a continuous liquid-impermeable surface. The bund (2) also comprises a fire-proof cover (100, 170) covering the wall (4) for fire and UV protection.