The population growth, industrial development and the quantity and quality growth of consuming products have increased the amount of generated solid wastes. In recent decades with the technology development in the integrated municipal solid waste management, the methods such as recycling, biological treatment, thermal treatment and sanitary landfill have been used. Although a combination of techniques and strategies of waste reduction is utilized, the existence of suitable site for sanitary landfill is necessary for the solid waste management. Landfilling is the most common municipal solid wastes disposal method in the worldwide. Selecting the suitable landfill site can prevent the inappropriate ecological and socioeconomic effects. Landfill site selection requires the analysis of spatial data, regulations and accepted criteria. In this regards the geographic information system and multi criteria evaluation methods can be used as efficient tools for managing and applying different information layers in site selection stage. The present municipal solid wastes landfill of Najafabad has encountered some restrictions due to the city expansion and proximity to Azad university. The aim of this study is to define the suitable landfill site for Najafabad municipal solid wastes using geographic information system and analytic hierarchy process. Three categories of physical, environmental and socioeconomic criteria were evaluated for landfill site selection. Each of these criteria were prepared as different information layers such as slope, surface and under ground water resources, land uses, residential areas, agriculture lands, power and water transmission lines, wells and springs, faults, water permeability, ghameshloo protected area, industries, flood plains, distance from city and waste generation centers, access ways and residential and roads visibility maps. Then, these layers were investigated by Boolean and fuzzy standardization methods. Weighing the information layers by fuzzy standardization method was done by the analytic hierarchy process. Superposing of the maps from Boolean logic showed that all parts of the study area are unsuitable for landfill establishment. By superposing the maps from fuzzy logic and considering the minimum required landfill area for 20 years, only two sites were identified as suitable with the area of 56 and 248 hectares. How ever, because of the proximity of these two sites to Tiran city, they are not suitable for landfill. There for, it seems that due to many restrictions in Najafabad, the possibility of common landfill sites should be investigated for adjacent cities. Key words: Municipal solid waste, Landfill, Boolean logic, Fuzzy logic, Najafabad
