NOVELTY - Pipework of the drainage network (19) is multifunctional. It is used in an alternating sequence to first draw out biogas (A) and then to inject leachate (I).    USE - For biotreatment and storage of diverse solid wastes, and in particular its gaseous and liquid effluent handling systems. Industrial, communal, agricultural and other wastes may be treated.    ADVANTAGE - The volume of biogas produced from the body of waste is increased. The biogas production phase is reduced and stabilization is accelerated, thus reducing operational costs. The installation is simple, multifunctional and low in capital cost.    DETAILED DESCRIPTION - There are three networks (9, 11) of drain pipes (19) separated by the waste (2) storage volumes (3, 4). Each network has two ends connected to pumps removing the biogas and/or injecting leachate. These are separated, and situated on either side of the waste storage volume. A vertical duct is situated at one or more of: each node of the drainage network, each free end of the network, between nodes and between nodes and free ends. Drain inclination is 5% between nodes or between a node and a free end. The subsequent drain inclination is inverted. Upper surfaces of the drains have openings (21) for biogas removal from the waste by suction, and for leachate injection. The drains are in drain trenches (8). A supplementary drainage network and its connections are detailed. The drains are used to reinject a gas into the storage volume, e.g. CO2, air or other gas. Three volumes (4) are stacked with at least three drain networks and a network for pumping excess leachate, with outlets connected to a single, vertical collection well. The plant may be complementary to an incinerator. It is a fermenting or composting treatment plant.    DESCRIPTION OF DRAWING(S) - The drawing shows the above plant.    waste (2)    storage volumes (3, 4)    drain trenches (8)    networks (9, 11)    drainage network (19)    openings (21)    biogas (A)    leachate (I)