Benching or Bench

The floor of a manhole into which the channel is set; the bench is raised so that it can drain to the channel.

Benchwall

The horizontal bottom of the manhole normally out of the flow path.

Bent Sub

An offset section of drill stem close behind the drill head that allows steering corrections to be made by rotation of the drill string to orientate the cutting head. Frequently used in directional drilling.

Bentonite

A colloidal clay sold under various trade names that forms a slick slurry or gel when water is added. Also known as drillers mud. See Drilling Fluid.

Berlin Construction Method

A sewer collection system developed in Berlin, Germany, whereby sewer laterals are brought to a manhole and then dropped into the sewer interceptor. This method of connecting laterals to sewer is more compatible with trenchless installations.