In order to investigate the groundwater ies aimed at defining the spatial contamination by solid waste disposal using both ies aimed at defining the spatial hydrochemical and geophysical methods, the Halkali (Istanbul) solid waste disposal site which was closed in 1994 was investigated. The disposal site lies on a ridge between two valleys filed with alluvium. A total of six boreholes were drilled on two lines across the Menekse valley adjacent to the Halkali site. Groundwater samples collected from these boreholes were analyzed for various contaminant parameters. The results indicate that TDS and chloride concentrations decrease horizontally away from the waste site whereas they increase with depth. Electrical soundings carried out at 12 locations yielded high resistivity values at the upstream part of Menekse valley while lower values were obtained from the locations near the leachate seepage points.