For the purpose of defining and establishing the grades of streets, avenues and alleys in the village, the top of the cast iron water table of the brick building on lot ten (10) of block three (3), original town of Stockton, is hereby fixed and established as a bench mark at an elevation of one hundred feet (100') and to zero, the base or datum plane one hundred feet (100') below such bench mark, shall be referred to all grades and levels in the village, and the same shall be recognized in all surveys and plans for grades of all streets, avenues and alleys and in establishing and describing the same. (1966 Code §7.502)