(A) All grades hereafter fixed in the Village shall be referred to the Chicago City datum or plane of lower water of Lake Michigan in the year 1847 as established by the Trustees of the Illinois and Michigan Canal which is forty and five hundred forty two-thousandths feet (40.542') below a square notch cut in the southwest corner of the top surface of the east stone balustrade of the main entrance to the Village Hall as standing on January 1, 1959.
(B) Said bench mark is also six hundred twenty and four hundred thirty eight-thousandths feet (620.438') above mean sea level as determined by the United States Coast and Geodetic Survey. (1965 Code, Sec. 22.01)