Clogging Factors and other questions for modeling Intakes On Grade

[tstadel]

I am a new StormNET user with a converted XPSWMM model that I am trying to re-enter all the inlet data that was lost in the conversion.

I have several questions regarding inlet modeling:

1. The clogging factor box is grayed out when I select a Neenah grate on grade. How can I apply a clogging factor to these grates?

2. I also apparently cannot apply a clogging factor to a curb opening inlet on grade - whenver I enter a value, it defaults back to 0%. Also, the Curb opening height box is grayed out with a value of 1.75 inches. Why can I not enter the actual curb opening height?

3. Finally, two of my on grade inlets are generating ERROR 600, even though the error message does not apply. I am attaching my model.

Thanks.

[Chris Maeder]

Note that we reviewed your model. Here are the answers to your questions:

1. The clogging factor box is grayed out when I select a Neenah grate on grade. How can I apply a clogging factor to these grates?

Answer : Note that the Neenah storm drain inlet capacity equations and performance curves do not account for clogging. Hence, we cannot include clogging in our computations, since we are using their equations and performance curves.

2A. I also apparently cannot apply a clogging factor to a curb opening inlet on grade - whenever I enter a value, it defaults back to 0%.

Answer : We reviewed your model and of the non-Neenah inlets that were in the model, none had this issue. Make certain you are using the latest StormNET. You can download the latest release from this link:
StormNET Downloads, STORMNET Software, stormnet tutorials, and stormnet documentation

2B. Also, the Curb opening height box is grayed out with a value of 1.75 inches. Why can I not enter the actual curb opening height?

Answer : The field you see is a place holder for On Sag inlets. As such, we then need to model the inlet as an orifice and the "area" of the inlet opening is used in the orifice equation. For On Grade inlets (like the ones in your model), this curb opening height is not used in the HEC-22 inlet equations.

3. Finally, two of my on grade inlets are generating ERROR 600, even though the error message does not apply. I am attaching my model.

Answer : StormNET did report the error correctly. However, it is software program (and not an engineer) so was unable to figure out how to fix it for you. Check pipe P1205. It has a negative (adverse) slope, so StormNET is stating that the pipe is not routing flow "downstream" from the inlet. I have fixed the model and attached it to this post. The model has a small positive slope for this link.

[tstadel]

In regards to item #3: I realize one of the connecting pipes has adverse slope, and I am interested in modeling the problems caused by this condition. I was under the impression StormNET had the ability to model adverse sloped pipes?

[Chris Maeder]

The fundamental issue is that we borrowed some of the EPA SWMM flow diversion element programming when we developed the On Grade inlet programming. EPA SWMM flow diversions do not allow the downstream link to have adverse slope (i.e., negative slope)--even when running hydrodynamically. So, presently the downstream link for On Sag inlets must have a positive slope.

However, we have on our development list to change how EPA SWMM handles this, and allow adverse slopes for the downstream link. This will be addressed in a future release of the software.