Unlike most civil engineering projects, trenching schemes are not confined to a recognized site but, by their nature, connect distant locations and involve working ina variety of rural and urban environments. In trench construction, one of the tasks for the engineers is to select a suitable route to minimize construction costs and obstructions. This paper develops a GIS based system to automate the process of routing and design of the underground electric distribution supply system. In the system, the ground surface and underground utilities are represented in several data layers (coverages). Each data layer is integrated with a relational database. Using network analysis, the system determines the optimum paths for routing the underground utilities. Through database analysis and spatial operations, the construction conflict points between the basic utilite layout and the selected route identified. The primary features of the system are as follows: (1) identify the routing alternatives along the existing streets, (2) determine the optimal position and dimensions of the underground utilities to minimize the influence on the existing public utilities and structures, (3) integrate construction schedule and design information to identify the relocation schedule of the existing public utilities, and (4) provide the distribution information of the existing underground utilities to reduce potential damages or fractures caused by construction excavation. This system improves the trench routing and construction efficiency by providing a logical and systematic manner for integrating construction considerations in design phase. Furthermore, compared with manual methods, the system significantly improves the computational efforts and increases the data accuracy and consistency.