Construction of a foamed polymeric manhole chimney

摘要

A stackable polymeric foam adjustment or grade ring is provided for the construction of the adjustment courses or manhole chimney portion of a sewer system. The adjustment ring is circular and may include concentric annular grooves on at least one surface and male portions corresponding in size and shape to the concentric annular grooves on a second surface. The adjustment rings are stacked one on another with the respective male portions being coupled within a corresponding annular groove to provide a manhole construction that is resistant to inflow, chemicals and freeze-thaw cycle damage.