Any drainage exits in the facility, hand basins included, must be fitted with barriers (screens or water traps, for example) of a suitable size to stop animals moving into or out of the facility through the drains. The accompanying note says a hand basin can use a water trap, and that where GM micro-organisms are present the barriers must be of a type and size that stops invertebrates crossing the facility boundary.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.