31.If the liner containment system for the disposal areas and the components of the leachate or water treatment system are below groundwater level, the disposal areas must, if the pressure exerted by the groundwater is likely to impair the integrity of the containment system, have a system that collects and evacuates the groundwater so as to reduce the pressure.
The groundwater collection system must
(1) incorporate all the components prescribed by section 25, except that
— the minimum thickness of the drainage layer must be 30 cm;
— the minimum diameter of the pipes must be 100 mm; or
(2) incorporate other components if the components are at least as effective as the components referred to in subparagraph 1.
The system must be designed to be monitored independently from the other collection systems on the site.
The operation of the groundwater collection system may be halted if the hydraulic pressure exerted by the groundwater is offset by the weight of the landfilled residual materials or by the liquid accumulated in the disposal areas and in the ponds or basins forming part of the leachate or water treatment system.