St. Charles, Illinois, maintains permanent benchmarks throughout the City. There are three runs: along the west side of the Fox River from Geneva to Elgin, on the east side of the City, and on the west side of the City. All three comply with bluebooking requirements established by the National Geodetic Survey (NGS) for vertical measurements and are classified as 2nd Order Class II benchmarks. The inclusion of the St. Charles Fox River run into the NGS connects the cities in the Fox River Valley in the Federal Register.
Each benchmark is driven into the ground and capped with a 3 1/4" domed cap with a magnet stamped with “City of St Charles Survey Benchmark”. It is enclosed in a 4 inch PVC tube capped with a standard monument access panel.
Survey Control Benchmarks map