Because those portions of the unincorporated area of the county within the limits of a sanitary district, organized and existing pursuant to the provisions of Part 1, Division 6, Section 6400, et seq., of the Health and Safety Code are also subject to the rules, regulations and methods of operation promulgated by such districts, the following districts, each consisting of the area lying within one of such special districts are hereby created for the purpose of this chapter, and the application of this chapter is or may be different within such districts as hereinafter provided, based upon such distinction. (Prior gen. code 3-61.6)