Bench Mark.

All grades and elevations hereinafter fixed and established and all grades and elevations that shall or may be hereafter established in the City of West Allis, Wisconsin, are and shall be described by reference to the level of the Milwaukee River as it was in the month of March, A.D. 1836, assumed as a base or datum line, from which all elevations and the height of all grades shall be measured in feet and decimal fractions of a foot, and for the purpose of fixing and establishing the level of said base or datum line, it is hereby ordained and declared that the same, in and for the City of West Allis, Wisconsin, is one hundred fifty-six and fifty-two one hundredths (156.52) feet below the top of the water table of the bank building at the northwest corner of S. 70 St. and W. Greenfield Ave. in the City of West Allis.