Supported by recent legislation (notably P.L. 92-500), the scope of water quality planning has expanded to include a range of comprehensive planning. In response to the needs generated by comprehensive water quality planning, a computer system called ADAPT(Areal Design and Planning Tool) has been developed. ADAPT is composed of a highly accessible large data file and a series of mathematical submodels which facilitate the storage and use of spatially arrayed data. Though originally implemented as part of a large water quality management study of the lower James River in Virginia where it was used in a variety of land-use/development and sewer/treatment plant design tasks, its flexible structure makes it broadly applicable to a wide range of environmental planning concerns. The basic structure of ADAPT is described, together with a description of its implementation.