Environmental geological and geotechnical investigations related to the potential use of Ankara clay as a compacted landfill liner material, Turkey I _ . Met Æ H. Akgu ¨n Æ A.G. Tu ¨rkmenog ˘lu Abstract Clay-bearing Upper Pliocene red clastics and Quaternary alluvial deposits occupy the Ankara basin. The clayey levels of the Upper Pliocene deposits, referred to as Ankara clay, is considered as a source for compacted clay liners due to their low coefficients of permeability and widespread distributions throughout Ankara. This study investigates the geological, geotechnical and mineralogical properties of the founding clayey soils at two sites of the Ankara region. The geotechnical index properties along with the hydraulic conductivities of the clayey soil samples collected from these sites were determined. A mathematical relation between the clay mineralogical content and hydraulic conductivity was established. The results of this investigation show that, from a geotechnical point of view, Ankara clay may be regarded as a highly suitable material for a compacted clay landfill liner given that its mineralogical compatibility with leachate is confirmed. Keywords Ankara clay Æ Compacted clay liner Æ Hydraulic conductivity Æ Clay mineralogy Æ Clay geotechnical index properties Æ Turkey Introduction The safe and reliable long-term disposal of solid waste residues is an important component of integrated waste management with the main purpose of preventing the possible contamination of soil, groundwater and surface waters by means of leachate resulting from the percolation of water through wastes moving into, through and out of the landfill migrating towards adjacent areas (Tchobanoglous and others 1993). Compacted clay liners providing low hydraulic conductivity values are extensively used to prevent rapid advective migration of various leachates from waste disposal sites, to cap new waste disposal units, and to close old waste disposal sites. Because the primary purpose of a compacted clay liner is to impede the flow of fluids, the most significant factor affecting its performance is its hydraulic conductivity (Daniel 1987, 1990). Environmental regulatory agencies require that compacted clay liners should be designed to have a hydraulic conductivity less than or equal to a specified maximum value [for example, 1·10 )9 m/s in the United States (USEPA 1993) and 1·10 )8 m/s in Turkey (Resmi Gazete 1991)]. Ankara is the second largest city in Turkey with a population of about 3 million inhabitants. There has been a distinct increase in the population between 1950 and 1975, and the population is estimated to be about 3.6 million inhabitants by the year 2010 as a result of mass migration from rural areas to the city. The daily total amount of waste generated in Ankara varies approximately between 0.56 to 0.62 kg/person, with an average of about 0.59 kg/person. For the last ten years, solid waste, including hospital waste collected from all of the municipalities of Ankara has been brought to the Mamak open dump site (Fig. 1), which poses serious environmental threats due to the lack of a waste containment system. Moreover, as the site is adjacent to a proposed large residential satellite called ‘‘Dog ˘ukent’’ to the east, alternative new landfill sites in and around Ankara need to be selected. To fulfil the landfilling needs of Ankara, the Ankara Metropolitan Municipal Authority developed a sanitary landfill project at Sincan-C ¸adırtepe with an estimated total waste capacity of 57,523,125 m 3 and a life span of approximately 20 years, to bring a solution to Received: 10 May 2004 / Accepted: 20 July 2004 Published online: 25 September 2004 ª Springer-Verlag 2004 I _ . Met Ziraat Bankası Genel Mu ¨du ¨rlu ¨g ˘u ¨, Tandog ˘an, Ankara, Turkey H. Akgu ¨n (&) Æ A.G. Tu ¨rkmenog ˘lu Faculty of Engineering, Department of Geological Engineering, Middle East Technical University, 06531 Ankara, Turkey E-mail: hakgun@metu.edu.tr Tel.: +90-312-2105727 Fax: +90-312-2101263 DOI 10.1007/s00254-004-1147-4 Environmental Geology (2005) 47:225–236 225 Original article