Surface sealing of the landfill site in Schönsee

Situation

The site of a former brickworks on Eslarner Straße was used as a municipal landfill. Previously, the site served as a clay pit; following its use as a landfill, it was used as a construction waste tip. Following the closure of the construction waste tip, the southern section was eventually continued to be operated as a soil disposal site. This subsequent use is important as the municipal area of the town of Schönsee is located within the Upper Palatinate Forest Nature Park, where open soil deposits are not permitted. Due to the significant seepage water contamination from rainwater, the Schwandorf District Office had determined that remediation was necessary. In the run-up to the planning phase, extensive preliminary investigations into the extent of the deposits were carried out using deep boreholes and dredging, in addition to settlement calculations for the remediated state. The groundwater level and quality were monitored at five groundwater monitoring points.

Solution

Over the years, trees and bushes have established themselves on the disused northern section of the landfill site. Approximately 350 existing trees were cleared during the winter months prior to the construction work, so that only the stumps needed to be removed during the construction phase. Once the vegetation had been cleared, work began on profiling the ground. During the course of further construction work, it was found that the relocated landfill body did not have sufficient bearing capacity for the installation of the geosynthetic clay liners. Soil improvement measures therefore had to be carried out. Once these were completed, the subgrade exhibited sufficient bearing capacity, allowing work to begin on laying the geosynthetic clay liners. The BAM-approved HUESKER HaTe Vlies served as the geotextile separation layer between the sand protection and the mineral drainage layer or the recultivation layer. For the majority of the surface sealing system, the use of the following system was agreed with the client and the approval authority:

• Base and levelling layer d = 30 cm
• Geosynthetic clay liner as sealing layer
• Sand protection layer d = 10 cm
• Geotextile separation layer (geotextile fleece)
• Mineral drainage layer d = 30 cm
• Geotextile separation layer (non-woven fabric)
• Reclamation layer d = 1.60 m
• Grass seeding and erosion control mats on the embankments
• The remaining area was covered with landfill sealing asphalt 

Advantages

The requirements for surface sealing were met using the geosynthetic clay liner. The former Schönsee landfill site has now blended well into the landscape.