A.   Established: There is hereby established the Alton city datum as one hundred sixteen and fourteen one-hundredths (116.14) as shown on the bronze marker near the northeast corner of the city hall building, placed at the south line of East Third Street, and twenty five feet (25') east of the west line of Court Square, immediately east of Alby Street. The city engineer shall start his levels for establishing bench monuments and city bench marks from said marker with an elevation thereof of one hundred sixteen and fourteen one- hundredths feet (116.14'), Alton city datum, are five hundred twenty and twenty seven one-hundredths feet (520.27') mean sea level. (1917 Code § 1560; amd. Ord. 2599, 12-17-1955)
   B.   Records: It shall be the duty of the city engineer to have accurate standard elevations and city bench marks established from and referring to the Court Square bench, and after they have been ratified and confirmed by the city council to make and keep a careful and complete record of such standard and elevation marks. He shall also make and keep a record of all the street grades heretofore and hereafter established by the city council. From elevations given in said records all public and private improvements shall be constructed. The elevation, bench marks and street grades contained in said records shall be the legal and only standard representing city datum. (1917 Code § 1561)