Error Conundrum

[DavidGMartin92]

I'm modeling a stormwater system that incorporates a series of detention/exfiltration "pods" and each pod has a storage pipe at the bottom of them. The issue I'm having is that when I increase the storage pipe size, the [93] error (Pond X Storage range exceeded by X.XX') fluctuates (e.g. storage range with a 12" pipe is exceeded by 0.29' vs. storage range with a 15" pipe is exceeded by 0.10' vs. storage with an 18" pipe is exceeded by 0.24'). What's causing this and how can I fix it for it to make sense with the size changes?

 

[psmart]

Your pond storage is being completely filled and the volume is becoming pressurized. This is generating warning [93] which indicates the effective WSE (pressure) in each pond.

The first step is to be sure you have defined all available storage and overflow paths that would be active at the reported WSE. For full details click the help button on the warning message, as copied below.

If you need further assistance please post the HydroCAD project file or email it to HydroCAD support.

[93] Warning:
Pond Storage range exceeded by xx'

The water surface elevation has exceeded the highest defined stage. All defined storage has been filled. Routing continues by applying additional head to the outlet(s), but without utilizing any additional storage. In essence, the pond has been extended upward as a pencil-thin chamber with no additional storage. (For details, see the pond's stage-storage plot.)

Important: For accuracy, you must define additional storage in order to accurately represent the physical situation being modeled. This may consist of additional stage-storage data and/or storage chambers, as required to describe the actual storage. The additional storage may also resolve other warnings (such as oscillations) that can result from inadequate storage.

This warning commonly results from a failure to provide storage data above the highest outlet device, such as an emergency spillway. Although you may not intend to utilize this storage, complete storage information is required in order to perform an accurate routing. When using custom stage-storage data, the situation is easily resolved by entering storage at one or more elevations above the upper-most outlet.

It is also possible that you have failed to include an overflow device for the pond, causing the elevation to rise beyond the expected level.

Note: If the storage volume is actually sealed (no additional storage is available) then the warning does not necessarily indicate a problem. Under these conditions the storage volume will become pressurized.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[beej67]

This is basically a design error. Increase your pipe size, or more generally your storage in each pod, until you don't get the error.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

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