(a) The official datum plane of the City shall be as follows:
The bronze plate, marked "U.S. Geological Survey Elevation 817.00 Feet" corrected to elevation 816.61 feet, as set in the south end of the east wall of the Severance Laboratory Building located on the northwest corner of the intersection of Lorain and College Streets. (1957 Code §107.01)
(b) All grades established shall have reference to the datum plane as set forth in subsection (a) hereof. (1957 Code §107.02)