Secondary containment has to be in place to hold and decontaminate any water spilt through (a) a primary container breaking, leaking or overflowing, or (b) overflow or leaks from an aquarium circulation system that may carry GMOs. The primary container share is (a) the volume of the largest container where there are ten or fewer, or (b) where there are more than ten, the combined volume of 10% of the containers taken from the largest (for example the largest 3 of 28). The guideline notes that where the total water to be held is small enough relative to the floor area that it cannot flow out of the facility, secondary containment may be unnecessary. It may take the form of bunding, or of trays placed beneath single tanks or tank racks, and an effluent decontamination system that collects floor drainage may serve as the secondary containment if it is big enough to hold and treat any overflow or leakage reaching the floor.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.