6.—(1) The map of a drainage board shall consist of such ordnance sheets as are necessary to show the whole of the district.
(2) Subject to paragraph (6) the ordnance sheets used by a drainage board in the compilation of the map shall be on a scale of not less than six inches to one mile.
(3) Where the map consists of more than one sheet, the sheets shall either—
(a)after any necessary trimming, be combined to form one sheet; or
(b)be kept together as separate sheets.
(4) Where the map is comprised in one sheet, the map and, where it comprises more than one sheet, each sheet shall have on the front thereof in a conspicuous position a statement that it is the map, or (as the case may be) one of the sheets comprised in the map, maintained by the drainage board (naming them) under section 35 of the Act.
(5) Where any hereditament in the district cannot be identified except by reference to enclosures or parts of enclosures on the map, and the ordnance sheets used in the compilation of the map do not indicate by a number any enclosure comprised, or of which part is comprised in the hereditament, the drainage board shall insert on the relevant ordnance sheet a number in respect of each such enclosure, but so that each number so inserted shall be different from the number assigned to any other enclosure on the map or, where the number is inserted on an ordnance sheet of the county series, the number assigned to any other enclosure in the same parish or district.
(6) The map shall show the external boundary of the district by a line of a distinctive colour, but the drainage board may, instead of showing it on the ordnance sheets referred to in paragraph (2), show it on additional ordnance sheets on a scale of less than six inches to one mile.
(7) Where an order under section 24(7) of the Act of 1930 is in force, the map shall show in a distinctive colour by edging, hatching or colouring within the boundaries thereof the portion of the district on the occupiers of hereditaments in which portion the order determines that no drainage rates shall be levied.
(8) The map shall contain an appropriate legend explaining the significance of the colours used thereon.