Pond Node Outlet Structure Question

[OxEng]

I am reviewing a design of an underground detention system that is using 96-inch diameter storage pipe. The design engineer is modeling the control for the pond node as an 18-inch diameter culvert for the primary outlet and routing a weir plate with orifices through it. However, the plan layout has the control structure shown as a 2-foot diameter manhole located downstream of the storage pipe with 45 feet of 18-diameter pipe connecting them.

It still appropriate to model it this way or should the actual outlet from the pond node be an 18-inch diameter culvert that then connects to a catch basin node representing the control?

 

[psmart]

As long as the weir plate is the effective control point, and the WSE remains equalized between the pipe storage and the control structure, modeling as a single pond is the recommended solution. It's easier to setup and produces more stable results than a 2-pond solution, which requires a tailwater-sensitive routing procedure because the effective outlet control for the pipe storage is in the downstream node.


Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[beej67]

It all goes down to how much flow that 45 ft of 18 inch pipe can convey. If it can convey the peak flow out of the facility without a significant head loss, then it's the right method. If it can't, then you've got a more complicated situation on your hands. Check the 100 year (or etc) flow from the facility in the model.

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