In the densely populated part of Nagytétény bay Metallochemia factory has been operating as a pollution source resulting from stack emission as early as since the beginning of the 1900's. The nearby residential properties were impacted by significant concentrations of heavy metals, which found their way also to the deeper strata of the soil. Our task was to perform the detailed environmental state investigation of the nearly 1,400 impacted properties located in an area of 3.5 km2 and to prepare a technical remediation action plan. For the execution of the task a complex GIS system was developed, to take the numerous design aspects (such as technological and horticultural condition of the objects on the properties, presence of public utilities, current and planned land use, percentage of built-up area, archaeological, cultural, protected natural and other restricted areas, objects, and morphologies, as well as pedological, geological and hydro-geological conditions) into consideration. For the work three series of aerial photographs, taken at different times, and approximately 20 thematic maps with different scales and projections had to be integrated into the system. Data processing was executed by ArcView GIS programme. This system made us possible to manage and evaluate the territorial relationships between the data, as well as to make design calculations, and to thematically represent the results by using previously developed logical functions. On the basis of the design considerations, environmental technical and horticultural remediation action plans were developed for each property. This study presents the main steps of fieldwork and the building of the GIS system without analysis of the collected data.