A system configured to replace a top portion of an under-dispenser containment unit embedded within a concrete island under a fuel dispenser. The system includes a mounting structure configured to be coupled to the top portion of the under-dispenser containment unit, and a dispenser sump top configured to be coupled to the mounting structure and the fuel dispenser. The mounting structure includes a series of angles and the dispenser sump top includes a frame having a pair of opposing end walls and a pair of opposing sidewalls, a central opening defined by the frame, a splash lip extending outward from a lower portion of each of the pair of opposing ends walls and the pair of opposing sidewalls, and a series of dispenser support flanges extending outward from an upper portion of the pair of opposing ends walls and the pair of opposing sidewalls.