A containment system for use adjacent to a selected region of a subterranean formation and comprising a plurality of laterally interlocked casing strings. At least one electrically conductive element is disposed along at least a portion of a casing string and is used for performing electrical time domain reflectometry. At least one protective element may be positioned between portions of adjacent casing strings of the barrier, and at least one electrically conductive element may be disposed at least partially within the at least one protective element for use in indicating at least one characteristic of at least a portion of the containment system. Electrical time domain reflectometry (TDR) may be used to indicate the at least one characteristic; for instance, TDR may be used to indicate leakage through the barrier or a discontinuity or void in a barrier filler material.