Abstract: A manhole base comprising a benching portion, an annular wall portion surrounding the benching portion and extending axially therefrom, the annular wall portion having inside and outside surfaces and at least two angularly spaced apart passages extending through the annular wall portion, each passage having inner and outer portions respectively, the inner and outer portions being disposed within the annular wall portion, the inner portions having respective inner openings in the inside surface and the outer portions having respective outer openings in the outer surface, the inner and outer openings being in communication with their respective passages. There is at least one canal in the benching portion for connecting at least two of the passages in communication with each other, the canal having an open top portion.

Abstract: The invention provides for a process for constructing manhole assemblies in an excavation or elsewhere, by the utilization of an outer form, a preformed manhole barrel which is positioned and propped within the outer form pipe stub inserted partially into the inside of the preformed manhole and resting under notches cut into the preformed manhole barrel, inflatable or rigid forms (or both) are used to form simple or complex channels in the concrete which is to be poured. The form ends are adapted to fit into the pipe stub ends or may abut other forms, where complex channels are desired. The forms are carefully positioned to allow for the proper height and grade of the channel in the completed manhole assembly. Concrete is poured and when it is set, the forms are deflated where applicable and removed to be reused.