The International Society for Trenchless Technology

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There are 211 entries in this glossary.
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Term Definition
Impact Moling

Method of creating a bore using a pneumatic or hydraulic hammer within a casing, generally of torpedo shape. The term is usually associated with non-steered or limited steering devices that rely upon the resistance of the ground for forward movement. During the operation the soil is displaced, not removed. An unsupported bore may be formed in suitable ground, or a pipe drawn in or pushed in behind the impact moling tool. Cables may also be drawn in.


The downward movement of water from the atmosphere into soil or porous rock. The unintended ingress of ground water into a drainage system. Water from the surrounding ground which enters through defects in pipes or joints in a pipeline or through the lateral connections, manholes or inspection chambers.

Infiltration/Inflow (I/I)

The total quantity of water from both infiltration and inflow without distinguishing the source.


Flow which enters the sewer generated by rainfall or an industrial discharge or other particular connection. Water discharged into a sewerage system and service connections from sources on the surface.

Interjack Pipes

Pipes specially designed for use with an intermediate jacking station.

Intermediate Jacking Station

A fabricated steel cylinder fitted with hydraulic jacks that is incorporated into a pipeline between two pipes segments. Its function is to distribute the jacking load over the pipe string on long drives.

Intersect Method

Horizontial directional drilling method that allows accurate installation over longer distances than can be achieved by conventional means. The Intersect method employs two rigs starting from opposite ends of the project to create pilot bores using conventional drilling tools. A magnetic source is substituted for the conventional steering tool in one of the rigs, which allows the other rig to accurately measure its position relative to the electromagnetic signal. The rig with the magnetic source tool advances toward the other rig until it intersects the bore and continues through the bore to the other side as the conventional tooling is retracted.

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