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PondPack Interconnected Ponds and Composite Outlet Structures Issue


I am trying to model 3 interconnected ponds all with composite outlet structures. It seems like I am doing something wrong because PondPack is having a hard time computing the rating curve for the first outlet structure. By a hard time I mean that the model is taking several hours to generate the curve (after 4 hours it did not get past TW elevation of 4.5 ft out of 9 ft). I am able to see the rating curves for the following composite outlet structures in the next 2 ponds when computed separately for verification purposes.

The first composite outlet structure consists of 3 weirs and a box culvert. Basically we have a culvert which discharges to a small 4ft tall weir and then to another 3 ft tall weir in series. The 3rd and last weir represents the roadway. The 4 ft weir is being modeled as an irregular weir and the 3ft one as a suppressed one. The weir representing the roadway is being modeled as an irregular weir approximately 330 ft long. For each pond, I am imputing elevation-area curves and with large catchment areas. The elevation-area curve for the first pond looks like this:

Elevation (ft) Interval (ft) Area (SF)
1 1 0
2 1 285506
3 1 338887
4 1 366592
5 1 1513573
6 1 2515509
7 1 4138611
8 1 6005119
9 1 8572238

Table above shows SF but area used for PondPack model was acres.

The cross-section for the irregular weir representing the road in the first pond looks like this:

Here are the screenshots for each component of the first composite outlet structure:

Weir one and XS:

Weir 2:


Weir 3 (Roadway) and XS:

Does anyone know why this issue may be happening? Any help is much appreciated. Thank you