Hettegger Entsorgung GmbH
SPP Spirk & Partner; Ziviltechniker GmbH, Wien;
3P Geotechnik ZT GmbH, Hallein
ALPINE Bau GmbH, Salzburg
June till October 2010
Hettegger Entsorgung GmbH operates a mass waste and residual waste landfill in the municipality of St. Veit in Pongau/Salzburg, Austria. The capping of the landfill was approved in 1998. The permit covered the capping and drainage of the embankment areas. In 2009, the cover lining system was erected in the filled areas. During operation, however, unacceptable quantities of leachate showed an insufficient sealing effect of the cover lining system.To improve the sealing effect, the cover lining system was taken up again and replaced by an alternative sealing system. A geosynthetic clay liner (GCL), a drainage mat and a geogrid were installed.
In summer 2010 the already recultivated areas of the landfill embankments were cleared. The existing embankment covering was removed from 0.30 m to 0.40 m and the subgrade for the bentonite mat was constructed at this level. The cover lining and drainage system was installed on this subgrade. As additional protection against root penetration, a geomembrane is incorporated into the GCL. The overlaps of the 5.20 m wide GCL were glued together on site to ensure both tensile strength and shear strength. A drainage mat was installed to collect and drain leachate on the surface of the GCL. The drainage capacity of the mat was proven to be sufficient for the next significant rainfall. The drainage mat also serves as additional protection for the GCL against damage caused by the cover material. A potential impairment of the sealing effect by displacement of the bentonite is thus avoided. To achieve stability in the embankment areas, an anti-slip reinforcement material was required. As much of the original cover lining system was used for this purpose.
To improve the sealing of the Hettegger landfill, the existing cover lining system was replaced by an alternative DVO- approved structure. With a reduction of the layer thickness from 2.40 m to approx. 1.30 m, the calculated permeability was reduced from 1x10-9 m/s to 7x10-11.