There is hereby established a datum plane or base line for all levels and grades in the City. The elevation of the datum plane or base line of levels and grades is assumed to be zero, in reference to which the following bench marks are hereby established:
(a) Bench Mark No. 1. Top of brass rod, stamped B.M., set in a concrete base eighteen inches below the surface of the lawn at a point four feet south of the southerly curb of Leslie Street and twenty-five feet east of the easterly curb of South Broadway. Elevation 685.130.
(b) Bench Mark No. 2. At Geneva, Ashtabula County, at the south entrance to the City Hall, in the top of the southwest corner of the concrete step, four inches above the sidewalk, a standard disk, stamped "GENEVA 1934." Elevation 671.151 feet.
(1930 Code Ch. IX, §§ 98, 99; 1968 Code §§ 48-1, 48-2)