18 CFR 12.51: Monitoring instruments.

(a) In designing a project, a licensee must make adequate provision for installing and maintaining appropriate monitoring instrumentation whenever any physical condition that might affect the stability of a project structure has been discovered or is anticipated. The instrumentation must be satisfactory to the Regional Engineer and may include, for example, instruments to monitor movement of joints, foundation or embankment deformation, seismic effects, hydrostatic pore pressures, structural cracking, or internal stresses on the structure.

(b) If an applicant or licensee discovers any condition affecting the safety of the project or project works during the course of construction or operation, the applicant or licensee must install and maintain any monitoring devices and instruments that may be required by the Regional Engineer or other authorized Commission representative to monitor that condition.