History of Salem’s vertical datum
The original town plat of Salem was filed with the Marion County Clerk on March 22, 1850. During the time of construction, there likely was a beginning point to control the elevations, but it is unknown.
The City of Salem was incorporated in 1857.
On June 7, 1876, the City Council passed Ordinance No. 105, which established a reference mark for the official Salem vertical datum. The reference was established at the northwest corner of a stone water table of the Chemeketa Hotel, located at the southeast corner of Commercial Street SE and Ferry Street SE. The reference mark was established as the “principal benchmark,” which is 48 feet above the “base of grades” for the city of Salem. The execution of all construction, field work, maps, and profiles of all projects within the city was determined from this reference and the “base of grades” datum that it represented.
In 1892, the U.S. Army Corps of Engineers established a river gauging station on the Willamette River at the foot of Chemeketa Street NE. The zero of the gauge was set at 2.38 feet above the city datum.
After heavy flooding in 1964, Salem Public Works conducted a major study of the flood aftermath. Findings of this study were published in June 1968. One of the recommendations was for the City of Salem to adopt the USC&GS vertical datum of 1929 (47) as its “base of grades.” On October 27, 1969, the Common Council passed Ordinance No. 160-69, adopting this datum.
Shortly thereafter, the current standard drawing was produced to show the relationships of the new datum to those that have been used in the past. Over the years, the drawing has been revised and redrawn into a CAD format and is now known as Standard Drawing No. 005.