The cover system of the mono-landfill Hamburg-Francop for disposal of dredged
material comprises a mineral liner of pre-treated fine-grained dredged material (‘METHAmaterial’) and an overlying drainage layer of pre-treated sandy dredged material (‘METHAsand’). Water balance and effectiveness of the cover with respect to minimising infiltration into the waste body have been investigated in a test field of 50 m length and 10 m width (lysimeter) from 1996 to 2015. Continous measurements of water flow (average annual discharge from the mineral liner of 14.9 mm with a dreasing tendency) and hydro-chemical measurements indicate that the mineral liner is performing well since more than 20 years after construction. Reasons are the low saturated hydraulic conductivity of about 1 * 10-9 m/s and the large thickness of the liner of 1.5 m; the high load of 2.5 m thick covering layers; the 1.0 m thick lateral drainage layer
constructed from relatively slowly-draining METHA-sand; the sufficient amount of plant available water in the recultivation layer; and, finally, to a certain extent the root barrier on top of the drainage layer, composed of compacted loam. The measurements are continued by Hamburg Port Authority as part of the long-term monitoring of the Francop site.@en