Scale model testing and calibration of City of Ottawa sewer weirs

This paper reports the results of a laboratory study of the effects of (i) manhole proximity to installation site, (ii) pipe slope (i.e., approach vel ocity), (iii) upstream head measurement location, and (iv) submergence on t he "hydraulics" of two types of sewer weirs used by the City of Ottawa. The City's streamlined form of broad-crested weir and its compound-shaped shar p-crested weir were initially calibrated for a "pipe straight"-arrangement (no upstream manhole is present) for a wide range of flow conditions at 0.2 %, 0.4%, and 1.0% pipe slopes. The calibration tests were then repeated wit h the weirs positioned immediately downstream of a model manhole structure ("manhole"-arrangement). Corresponding data sets were compared to determine the effects of (i) approach velocity and (ii) manhole proximity (for two d ifferent shapes of manhole "benching") on the respective weir discharge coe fficients.