5.3.1 Impressed Current Systems
Impressed current CP systems are typically installed as retrofitted systems to existing UST systems. They are not used on new installations.
Impressed current systems must be designed, installed, operated and maintained so that DC (direct-current) interference to or from any underground structure (e.g. utility lines) is minimized.
Readings for impressed current systems must include instant-off potentials.
Impressed current systems shall be tested annually, as well as inspected and evaluated by the Class B or Class C operator at least once every sixty (6) days to ensure that the equipment is providing adequate current in accordance with its design.