Taper is the upper part of a tapered manhole where its width gradually narrows. A tapered manhole is used to provide more room to work in the chamber once the worker has passed through the manhole cover. Trenchless construction workers often enter manholes when performing installation or rehabilitation tasks.
Trenchlesspedia Explains Taper
Tapering is a design feature in many manhole structures. A cross-section view of a manhole with a taper shows one edge angling at the top of the shaft toward the manhole cover. Manholes are used to access underground infrastructure such as municipal sewer systems. While the entranceway through manhole covers may be of a limited size, the working space below can be much wider.
Some utility companies, such as Sydney Water, have made tapered manholes a standard requirement. A typical manhole may taper from a width of 1,050 millimeters (41.33 inches) to 600 millimeters (23.62 inches) at the opening. Working with utility companies and accessing manholes is a major part of the trenchless construction industry.