Abstract: An insert system for repairing defects in underground conduits in situ comprises a tubular inner liner of stiff material having a generally smooth inner surface and a plurality of integral outer circumscribing ribs defining a plurality of valleys between the ribs. An outer sleeve circumscribes the inner liner and is formed of an elastomeric material. A mid-layer of reinforcing woven material is wrapped about the inner liner within the outer sleeve. A hardenable resin saturates the mid-layer and fills the valleys. The resin bonds to the inner liner to form a structural insert, and the outer sleeve provides a deformable seal against an inner surface of a conduit when the insert system is operatively positioned.