Where the alluvial clay was at its shallowest, after having  removed the refuse, a separator geotextile was placed to   provide a separation filter layer below a drainage blanket of   single-sized 37.5mm crushed rock. Over the deepest clay   area, a drainage blanket (0.4m) was placed directly onto the   stripped ground. Vertical band drains were then driven   through to a depth of 6-10m to shorten the period for   dissipating pore water pressure below the embankment. 

Paralink 300 was then placed before completing in   controlled lifts the remaining 2.2m of drainage stone.   Paralink was introduced to take up the stresses imposed by   the settlement of the embankment and thereby even out   any differential movements. Instrumentation has been installed under the embankment   to monitor the settlement profile, edge movements and pore   pressure. No significant displacement has been recorded   proving the effectiveness of the solution proposed.