Benchmarks

For information about the Portland ONLINE BENCHMARK BOOK, call the Survey Office at 503-823-7152 or FAX to 503-823-7371 or email us at: Ken.Holzworth@pdxtrans.org. The mailing address is:

City of Portland, BTE&D Survey
1120 SW Fifth Avenue, Suite 800
Portland, OR 97204

Benchmarks

Benchmarks are survey markers that provide a point of particular elevation used as a reference for determining elevations of other points in a survey. They are used by surveyors, engineers, planners, and contractors for establishing elevations for planning, designing, and/or construction of various projects. For more information about differential leveling, the process of transferring benchmark elevations to a project site, click here.

The City of Portland is responsible for establishing and maintaining a network of benchmarks throughout the city, each having a known elevation expressed in feet in the City of Portland’s own datum (established in 1896).

Most of the City of Portland’s Benchmarks are brass disks about 2 ½" in diameter, and all are marked "City of Portland Bench Mark No. nnnn " and usually set in the curbs of streets. Occasionally you’ll see larger disks of 3 ¾" diameter which are "Class A" monuments, and some benchmarks are set in retaining walls, bridge wing walls, culvert headwalls, concrete steps, or wherever the most stable and accessible placement was determined to be for a specific location.

You might also see benchmarks similar to those of the City of Portland’s but with another governmental agency’s or private firm’s name stamped on it. Occasionally the City of Portland Benchmark Book will refer to these monuments and provide elevations, but more often you’ll have to contact the appropriate institution for more information.  The benchmark numbers the City assigned to outside agency monuments are for indexing purposes only; PDOT does not stamp a City of Portland benchmark number on other agencies' monuments.