In this chapter, the following terms have the meanings indicated. Terms Defined. “Approving Authority” means the Secretary of the Environment or his designee. “Community sewerage system” means any system, whether publicly or privately owned, serving two or more individual lots for the collection and disposal of sewage or industrial wastes of a liquid nature, including various devices for the treatment of the sewage and industrial wastes. “Community water supply system” means a source of water and a distribution system, including treatment facilities and storage facilities, whether publicly or privately owned, serving two or more individual lots. “County plan” means a comprehensive plan and all amendments and revisions of it for the provision of adequate water supply systems and sewerage and solid waste disposal systems and solid waste acceptance facilities throughout the county to include all towns, municipal corporations, and sanitary districts in it. “Developer or subdivider” means a person, persons, partnership, firm, corporation, or cooperative enterprise undertaking or participating in the development of a subdivision. “Fifty-year flood plain” means that area which would be inundated by storm water runoff equivalent to that which would occur with a rainfall of 50-year frequency, and is designated in the soil survey for a particular jurisdiction and to include the additional drainage which would accumulate from developed areas above the site under consideration. “Individual sewerage system” means a single system of sewers and piping, treatment tanks, or other facilities serving only a single lot and disposing of sewage or individual wastes of a liquid nature, in whole or in part, on or in the soil of the property, into any waters of this State, or by other methods. “Individual water supply system” means a single system of piping, pumps, tanks, or other facilities utilizing a source of ground or surface water to supply only a single lot. “Lot” means a part of a subdivision or a parcel of land used as a building site or intended to be used for building purposes, whether immediate or future, which would not be further subdivided. “Lot area” means the total usable area which is included within the rear, side, and front lot lines but to exclude those areas: Covered by mean high tide; In an existing or proposed public road; and Having land sloped exceeding 25 percent and areas located within the 50-year flood plain. “Lot width” means the horizontal distance between the side boundaries of the lot as measured at the: Line which forms the roadside boundary of the lot; Building setback line; or Sewage disposal area, if a minimum 20-foot wide area extending from the roadway to the individual water supply and sewage disposal area is delineated for access to those systems. “Minimum ownership” means the minimum ownership area which may be required to be titled and recorded in the name of a person or persons, partnership, firm, corporation, or cooperative enterprise when community water or sewerage systems are not available. More than one lot may be included in the minimum ownership area. “Preliminary plan” means a drawing of a proposed subdivision containing information as required by these regulations for review by the Approving Authority. “Record plat” means a completed drawing of the subdivision which contains all pertinent information required by these regulations and any other data necessary for recording plats. “Soil survey” means the scientific inventory consisting of soil maps, soil unit descriptions, classification in the National System, and interpretations for use, as conducted by the National Cooperative Soil Survey by the U.S. Department of Agriculture, Soil Conservation Service, in cooperation with the Maryland Agricultural Experiment Station. “Subdivision” means the division of a single tract, tracts, or other parcels of land, or a part of it, into two or more lots, for the purpose, whether immediate or future, of sale or of building development. Subdivision includes a change in street lines or lot lines, unless the Approving Authority determines that the change will not adversely affect the safety and adequacy of well sites or sewage disposal areas of the subject lot or adjacent lots. However, division of land for agricultural purposes into parcels of more than 3 acres, not involving any new street or easement of access, may not be included within the meaning of “subdivision”.