Abstract
Geotechnical engineers and engineering geologists are often involved with siting facilities where the potential for ground subsidence exists. The potential for subsidence could be a result of ground-water withdrawal, deep mining, hydrocarbon extraction, or salt solution mining. In order to monitor for detection of subsidence in these environments, bench marks are often installed. The bench mark design, location, and depth are governed by the purpose of the subsidence monitoring program. The geotechnical engineer or engineering geologist generally requires a high order of accuracy of vertical control, which includes repetitive optical leveling over an established network of bench marks to obtain accurate and precise data. However, the standards and widely used specifications for precise leveling recognized throughout the geodetic community consist of many more requirements than generally understood by the geotechnical engineer or engineering geologist.
