This document specifies the measurement of pore water pressures and piezometric levels in saturated ground by means of piezometers installed for geotechnical monitoring. General rules of performance monitoring of the ground, of structures interacting with the ground, of geotechnical fills and of geotechnical works are presented in ISO 18674‑1. If applied in conjunction with ISO 18674-5, the procedures described in this document allow the determination of effective stresses acting in the ground. This document is applicable to: — monitoring of water pressures acting on and in geotechnical structures (e.g. quay walls, dikes, excavation walls, foundations, dams, tunnels, slopes, embankments, etc.); — monitoring of consolidation processes of soil and fill (e.g. beneath foundations and in embankments); — evaluating stability and serviceability of geotechnical structures; — checking geotechnical designs in connection with the Observational Design procedure. NOTE – This document fulfils the requirements for the performance monitoring of the ground, of structures interacting with the ground and of geotechnical works by the means of piezometers, installed as part of the geotechnical investigation and testing in accordance with References [4] and [5] This document relates to measuring devices, which are installed in the ground. For pore water pressure measurements carried out in connection with cone penetration tests, see ISO 22476-1.