Storm and Sanitary analysis - Closed Detention through Underground Exfiltration

[rsucre4ST9M]

Hi Everyone,

I am trying to model an underground detention system with no outfall discharge. I am using the hydrodynamic flood routing method (because the other ones don't seem to work for this scenario).

Since I am using the hydrodynamic method and the system is supposed to not have any outfall I am trying to set up the outfall in a way that it doesn't get any inflow so that it doesn't impact the system capacity. However it is creating unstable conditions and when I run the model it gives me a super high water elevation. I am thinking it is probably because the system needs more storage because when I add significantly more it seems to work. 

Adding more storage barrels to my system seem to work. Also changing the inlet an outlet elevations of the pipe conveying water to the outfall helps. When I set up the these pipes high to avoid having a discharge the problem occurs. It also occurs when I reduce my storage capacity removing underground storage barrels. 

Do you have any idea on how can we set up such a system in SSA? 

[rsucre4ST9M]

See attached max water elevation. It went up to a nonsense level because I change the outfall inlet and outlet elevations. It also happened when I reduce the storage barrels on the storage nodes. 

[arodriguezDQBHW]

Graph the node time and head and determine at what time the systems goes beserk. if it is a time=0 start the system with water level = 0. Sometimes for example if setting a manual outfall tailwater elevation, at time=0 the flow in the outfall reverses through the system and that sometimes becomes the maximum flow reported in the model. To avoid this I either start reporting after some time has elapsed or put a check valve in the outfall to prevent the reverse flow. Not saying that is your problem though...