We take it to the extreme – geosynthetics also secure landfills in vertical direction

Sealing the quarry wall at the Borgholzhausen landfill site, Germany

The district of Gütersloh needed to create a local disposal zone for construction debris and soils to minimize the impact of the waste transport process and the associated heavy vehicles on the area. Landfill operator GEG (Gesellschaft zur Entsorgung von Abfällen Kreis Gütersloh mbH, Germany) manages the Borgholzhausen landfill for inert waste. The site is a piggyback landfill on a previously closed landfill body. In a resource-saving solution, the area of the new landfill takes volume from an abandoned limestone quarry. The back of the landfill is formed by the vertical excavation front of the quarry to minimise and optimise land use. The surface of the vertical front is rough and uneven due to the irregular weathering of the layered rock.

Under such challenging boundary conditions, special engineering measures are required to ensure that the base sealing of the new landfill body meets the high standards for sealing systems for landfills in Germany even at the vertical face of the quarry wall, thus preventing the release of landfill leachate. The construction and quality assurance measures were planned by Asmus + Prabucki Ingenieure Beratungsgesellschaft mbH.

A central element for lining the vertical quarry wall is a successive construction progress of the sealing system. It is not possible to install a mineral base seal vertically on the steep face, as required by the Landfill Ordinance for base seals. This raised questions of stability. To resolve them, the team installed the mineral liner in single steps in a stable, compacted trapezoidal cubature, each 4m high, with an inclination of 1:1.5 successively with the waste body.

Structured HDPE geomembranes (Carbofol® PEHD 510 2.5 MF/MF) were then selected for the project and approved by the German Federal Institute for Materials Research and Testing (BAM) as a polymeric sealing component. To ensure that the system offered sufficient shear force transfer on these short but steep slopes, a protective nonwoven geotextile (Secutex® RZ 2221) was also approved by BAM to prevent sliding failure in the shear joints of the sealing system. The engineering firm Bauberatung Geokunststoffe GmbH & Co. KG performed the sliding safety calculations for the design.

The protective effectiveness of the protective nonwoven Secutex® RZ 2221 was shown in load plate tests (EN 13719) with the project-specific geosynthetic components and soils. Naue has performed various similar tests with Secutex® nonwovens, showing how their cushioning properties can prevent inadmissible deformation of HDPE geomembranes even under high loads and coarse drainage materials.

Sealing the quarry wall at the Borgholzhausen landfill site, Germany

The construction of the intermediate sealing for the older inert waste landfill started in 2009 by sealing the 1st construction section. Subsequently, the 2nd construction stage was carried out as intermediate sealing against the old landfill body and successively on the vertical quarry wall in the described procedure. By 2021, more than 31000m² of geosynthetics from Naue GmbH & Co. KG were installed at the Borgholzhausen landfill site by Naue Sealing GmbH & Co. KG.

The tests on the quality of the products and the installation quality on the construction site, which are performed according to a site-specific quality management plan, have proven that the components and the installation work meet the highest standards; thus, ensuring the protection of the environment and the local population. ECOWEST, the operator of the Borgholzhausen landfill, can continue to ensure regional disposal security in the face of declining residual volumes for inert waste throughout Germany.