Tensar stabilisation solution helps drain lagoon

Tensar stabilisation solution helps drain waste sludge lagoon, in Lower Saxony, for remediation

A 13,000 sq.m., 6 to 8m deep waste sludge lagoon in Lower Saxony, Germany, required drainage and capping prior to being returned to amenity use.

By laying Tensar geocomposites and geogrids, safe and stable platforms were created in a very short time to facilitate access for drainage and create a base for a soil cover layer.

The lagoon had reached maximum capacity and the surface had an undrained shear strength of 10 kPa, a water content of 360 - 440% and could not support the weight of a person.

Rolls of Tensar SS40-G geocomposite (Tensar SS40 geogrid factory bonded to a non-woven geotextile) were first laid over the surface in overlapping sheets, secured by cable ties.

This enabled foot access so that debris could be cleared from the lagoon surface as the sheets of geocomposite were laid out; this phase was accomplished in just two days work.

Then a sandy gravel layer 350mm thick was installed over the geocomposite, followed by Tensar SS30 geogrid, rolled out at ninety degrees in direction to the geocomposite layer.

This was covered by a further 350mm layer of granular fill, and drainage pipes installed within the fill to discharge the water.

This 70cm of granular fill, reinforced with a double geogrid/composite layer, safely supported heavy construction machinery and the final 600cm of topsoil cover.

Consulting engineer: GTU Ing.-Buro Hannover, Prof Biczok.

Contractor: MTW Mittelweiser Tiefbau Warpe.

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