Switzerland. Canton Aargau. Kölliken. The Kölliken hazardous waste landfill (SMDK) is the largest contaminated site in Switzerland. It is located in the middle of a residential area. It began operation in 1978 and was shut down from 1985 due to odor and dust emissions and made safe for the short term. It transpired that the landfill was threatening the closest water table. The remediation operation, officially approved in 2003, involves creating an appropriate infrastructure (support-free hall, rail connection etc.) and excavating a total of 500,000 tonnes of waste. For the full remediation of the hazardous waste landfill (SMDK), the SMDK decided to excavate the hazardous waste accumulated between 1978-1985 under the protection of an airtight steel-framed hall and to dispose of it in accordance with the applicable legislation. Based on a new concept of a large-surface, column-free hall, the company ARGE Phoenix opted for a layered, flat-surface excavation instead of proceeding with vertical extraction as originally intended. This eliminates the risks connected with a steep slope. The landfill was removed layer by layer starting from the top. One of the advantages of this approach is that the material can be sampled before excavation and can be divided up into various categories. The remediation work is being carried out under the cover of several halls, allowing the landfill body to be dismantled without releasing any emissions. The main supporting structure for the dismantling, processing and storage halls comprises 29 two-hinged arches with tie rods spanning the landfill site lengthwise. The load is transferred to the substrate using reinforced concrete walls and reinforced drilled-in caissons. Prestressed anchors secure the northern slope and Safenwilerstrasse located in the south. The excavated waste is transported away by rail. The work is expected to be completed in 2017. Kölliken (Koelliken) is a municipality in the district of Zofingen in the canton of Aa