A Surface sealing system - a geomembrane and combined a leak control system detects damaged spots in the geomembrane and reduces the risk of hazards.
The landfill Senzig was in operation from 1968 until 2002. About 1,670,000 m3 of municipal, construction, commercial, and industrial waste was deposited on an area of 11.7 ha. A geological barrier and a base liner do not exist; the groundwater level is high. Thus, after closure, remediation measures were obligatory. As the volume of the landfill body exceeds 500,000 m3 the remediation had to be executed following the requirements for the landfill class II of the German landfill ordinance. Accordingly, the landfill had to be covered by a sealing system with two sealing elements. However, in the case of Senzig the authority approved the substitution of the second sealing element by an electronic leakage control system (LCS).
The LCS detects leaks > 5mm and the polymer liner can be repaired locally. The LCS consists of a grid of voltage sources installed above and electrode-sensors installed on both sides of the polymer liner. The voltages sources feature a grid of approx. 30 m, the sensors a grid of 10 m. The polymer liner acts as an insulator as electricity is not well conducted. In case of a leak the conductivity increases as the water percolating through the leak promotes conductivity. The electric potential changes, the differences in the potential provoked by a leak in the liner can be measured by the installed sensors. Overall, the LCS reduces the risk of hazards.
Twenty-five percent of the installation of the sealing system was financed by ERDF funding.
The financial resource needed for the all remediation measures was approximately 5,000,000 €. The leak control system is about 10,000 € per hectare.
Evidence of success
This practice guarantees the intended performance of the polymer liner. Leaks can be detected and repaired afterwards. In the case of Senzig already during the quality check a leak caused by the construction measures was found. By equipping the old landfill body with a surface sealing layer a long term groundwater protection is guaranteed, even though a basic sealing not exists and the pollution of groundwater decreases slowly caused by the special geologic relationship at the site.
The practice requires a significant knowledge and experience in the installation of the leak control system. The used materials had to be approved by the German Federal Institute of Materials Research and Testing. The guarantee for the leakage control system is limited for 30 a.
Potential for learning or transfer
About 500,000 landfills exist in the EU. The EU landfill directive is decisive for the minority of the landfills (< 10%). Despite of the huge number of landfills, no information of remediation is given in the directive and there is no technical guideline or handbook on European level. This good practice describes an example for remediation of a landfill. The design of the remediation measures followed a risk based approach. It is replicable for landfills with a larger volume, where waste was disposed which can potentially pollute the groundwater. In Germany the covering by a surface sealing system with two sealing elements is obligatory for landfills for non-hazardous waste with higher pollutant level according to the German landfill ordinance. It can also been applied for older landfills without a basic sealing system. The practice is good for cases where an effective protection of the environment from landfill caused groundwater pollution is necessary.
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