Summary

After a conduit is installed in a trench and has been backfilled, but before any surface construction begins, it is common practice to check duct quality because certain plastic conduits can become oval-shaped, pierced or broken. Recommendation ITU-T L.73 describes inspection methods such as the use of test mandrels and closed-circuit television (CCTV) systems to check duct quality, and also describes various methods that are utilized to repair underground conduits. Repairing methods without digging, called "trenchless techniques" are introduced, and traditional repairing methods (dig and replace) is also presented. Additionally, guidelines for selecting appropriate repairing methods are proposed. It is expected that this Recommendation will provide alternative solutions for inspection and repair work.