Ali Vosoogh - Ph.D Candidate, Department of Hydraulics and Environment, School of Civil Engineering, Iran University of Science and Technology, p.o.box16765-163, Narmak, Tehran, Iran
Akbar Baghvand - Associate Professor, Graduate Faculty of Environment, University of Tehran, No. 23, Azin St.,Qods St., Enghelab St., Tehran, Iran;
Abdolreza Karbassi - Associate Professor, Graduate Faculty of Environment, University of Tehran, No. 23, Azin St., Qods St., Enghelab St., Tehran, Iran

Nowadays, with the ever-increasing growth of the population and thedevelopment of various industries, we are experiencing an increase inenvironmental problems, resulted from man–made contaminants (such as urbansolid wastes, wastewater, etc).Generally, the ease of the exposure of groundwater to aquifers is determined bythe vulnerability of these waters. The vulnerability assessment is a processthrough which we can distinguish those areas with the lower vulnerability fromthe ones with the higher vulnerability. Hydro geological parameters which areeffective in polluting ground waters and also presented in Modified DRASTICmodel involve: Depth to groundwater surface (D), Recharge (R), Soil media (S),Topography (T), Impact of vadose zone (I) ,Conductivity of aquifer Hydraulic(C),the effect of Land use activity(L).This study aims at zoning the pollution potential of Mashhad aquifer by using theModified DRASTIC method and GIS software in order to locate and select somenew landfill sites as well as to assess the previous existing ones.The results showthat new and existing landfill sites for solid waste disposal in Mashhad siteselections were wrong, while they are located in high vulnerability zones andwhere the risk of groundwater pollution is high.

waste; vulnerability; pollution; landfill; Modified DRASTIC