Underdrain pipes in SSA connect to sturm structure

[cadman1957]

Good morning, all...

Due to water quality requirements in a project, I am modeling a bio-retention pond in SSA which includes a gravel storage area below the "hard" bottom of the pond. Stormwater is conveyed out of this gravel area via perforated pipes that connect to an overflow unit in the center of the pond. The water is conveyed to a downstream drainage stricture and to a standard detention pond.

My problem is that I can model the gravel area and the pipes just fine in the storage curve for the pond, but I don't see any way to connect the underdrain pipes to a structure, so the model is left with just allowing the underdrain water to exfiltrate, which isn't the case. Can anyone tell me how to connect the pipes to my structure?

Thanks,

Tom