(a) Concrete markers, at least four inches in diameter and thirty-six inches in length with a one-half inch round steel rod cast in the center, shall be sunk in the ground at each corner, angle, intersection or other location required by the Subdivision Control Act. The location of all monuments shall be shown on the final plat map in accordance with the Subdivision Control Act. All monuments shall be sunk and set flush with the finish grade.
(b) Iron pipe stakes not less than one inch in diameter and eighteen inches in length shall be sunk in the ground at all lot corners, at points of tangency of curves and, as required by the City Manager, at suitable intervals along curves. Steel stakes of other cross-sections, at least eighteen inches in length, may be used in lieu of iron pipe with the written approval of the City Manager.
(c) All United States, State, County or other official bench marks, monuments or triangulation stations in or adjacent to the proposed subdivision shall be preserved in precise position.