A 6-inch Parshall flume in a 72-inch diameter domed top fiberglass Packaged Metering Manhole prior to commissioning.  

Sediments have collected in the inlet end adapters as gravel, debris, and other materials have been washed down into the line prior to commissioning and start-up.  

Under normal flow conditions, the energy of the transition from the round pipe to the rectangular end adapter provides sufficient turbulence and transport velocity to allow all but the densest sediments to stay in suspension.