European Journal of Operational Research 38 (1988) 339-349 339 North-Holland Case Study Selecting transfer station locations for large solid waste systems Omer KIRCA and Nesim ERKIP Dept. of Industrial Engineering, Middle East Technical University, Ankara, Turkey Abstract: In a city with a population over 6000000, solid waste collection activities require a lot of attention. The resources used for collection and transport, trucks and labor, can be utilized more effectively if waste is transported to the disposal area via transfer stations. The location of transfer stations becomes especially important when the daily average of solid waste to be transferred is around 6 000 tons and disposal areas are at least 30 kilometres away from the metropolitan. A general mathematical programming approach with four stages is proposed to determine the locations of transfer stations. Certain modifications are required for the case considered, all resulting in a model which identifies the trade-off between costs of carrying the waste by different transportation modes. The identification of the trade-off requires the estimation of relative cost values rather than individual costs. On the basis of the results obtained, economic feasibility of different alternatives can be evaluated upon the availability of cost information. The apphcation of the model to istanbul is summarized together with the details of analysis. Keywords: Facilities/equipment planning, location, government, services, waste disposal 1. Introduction Two main tasks performed in a solid waste system are collection of waste from the districts and transportation of waste to landfill areas, or to waste processing plants, such as recovery plants, composting plants and incinerators. The collection is usually performed by some specially equipped, expensive trucks of varying capacities. We will This research is a part of project No: 85-01-00-01-06con- ducted at System Sciences Research Center, (SIBAREN) Mid- dle East Technical University. The authors would like to acknowledge other members of the project team, ~. Be§eli, M. Denizel, Prof. Dr. H. Do~'us~Sz,N. Karabakal, Prof. Dr. O. Saat~io~lu, H. Siiral, A. Toker and Assoc. Prof. Dr. E. Ulu~,, and Mr. Atanur Oguz, General Secretary of Istanbul Metro- politan Municipality, for their valuable comments and support. Received June 1987 name these trucks collection vehicles. The same trucks are used to transport the waste to the appropriate plant or landfill area, which are far away from the central metropolitan area for known reasons of public safety and environmental pro- tection. An efficient way of performing the transport activities is to employ transfer vehicles that will carry the collected waste to landfill areas or to waste processing plants. Installing transfer sta- tions at critical areas will enable the desired effi- cient operation as the collection vehicles will transport the waste to transfer stations and trans- fer vehicles (which have a lower operating cost than collection vehicles) will transport the waste from the transfer station to the desired area. Sav- ings are obtained by switching to a transportation mode with lower operating costs. Moreover the following benefits are obtained: 0377-2217/88/$3.50 © 1988, Elsevier Science Publishers B.V. (North-Holland)