The intent of comprehensive studies is to develop economical projects for the present and future collection, treatment and disposal of sewage from one or more municipalities or any portion thereof. Comprehensive studies are intended to include areas of present or projected high densities of population, including a natural drainage area covering a major portion of a sub-basin. Such studies are not intended to provide for minor sewer extensions or for sewer plans for small subdivisions or small areas, nor for the preparation of detail design and engineering drawings, specifications and contract documents.