Large sewer lines with diameters upwards of around 800/1200 mm can be manually refurbished by repairing the interior, specifically the invert. Gruner Böhringer AG has handled the design and implementation of such projects for the Canton of Basel-Stadt Public Works Department since 2005.
The damaged invert is first stripped by ultra-high-pressure water jetting and the waste material removed from the sewer. A suitable lining material, e.g. ceramic tiling, is then precision-laid to gentle falls in a special mortar bed. Tensile tests are performed to verify adequate adhesion to the existing concrete. Sewage flows are diverted for the duration of works.