Hello,

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:

Culvert:

Weir 3 (Roadway) and XS:

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

Sergio