The tocElevation is the single most important surveyed value for a MonitoringWell. Every field water-level measurement is taken as depth below the TOC; subtracting that depth from tocElevation yields the groundwater elevation used in trend analysis and potentiometric surface maps. If the casing is cut or raised, tocElevation must be resurveyed and updated to keep historical water-level data comparable.
Technical section
Data model, API, and internals — visible to developers.