Sonoma Municipal Code Ch. 1.16 City Base or Datum

The base or datum in the city for the purpose of providing a uniform system of elevations for streets, sidewalks, curbs, sewer grades, etc., is established as follows:

Datum shall be tide water as indicated by the United States Surveys, especially its “benchmark,” a circular metal plate or disc sunk in the brickwork of the store building at the northeast corner of Napa Street and First Street East. The elevation of the benchmark is given as 83 feet. This benchmark is 60 or 75 feet easterly from the east side of First Street in the building now known as Duhring’s Building. The exact point in the benchmark is a horizontal line in the middle. This shall be known as the initial benchmark. Its elevation shall be 83 feet.

From time to time as surveys progress, the city engineer shall take the elevation of some object not liable to be moved, record its elevation with reference to the initial benchmark, and describe it in such a manner that it may be recognized, sign his name as having so recorded it, and such new benchmark shall be regarded as a part of the system. (Ord. 139 § 1, 1914).