Method of installing subsurface barrier

A method of installing a subsurface barrier, comprising:

• emplacing a first casing having at least one male interlock structure and a plurality of female interlock structures defining recesses adjacent to a zone of interest;
• emplacing a second casing having at least one male interlock structure and a plurality of female interlock structure recesses adjacent to said zone of interest, such that said at least one male interlock structure of said second casing is received by at least one female interlock structure recess of said first casing;
• and
• forming a seal between said first casing and said second casing to form a continuous subsurface barrier.