Question regarding Modeling Retention basins in SSA 2014

[loretom]

I have been trying to model a storm drain system with SSA 2014 that contains a Retention (not Detention) basin.  I think I'm entering everything okay, but it continues to ask me for an outfall.  If I add an outlet it seems to work depending on the pipe size what elevation I use for the outfall.  I have seen models that other people have done without an outfall and they work fine, but if I do it it tells me that no outfall has been designated for the system and it won't run.

What am I doing wrong?

I tried attaching my file, but he system said it does not accept the .spf extension.  How can I attach the file?

Thank you in advance.

Miguel

[wfberry]

Rename the to suffix to something like .txt.

Surely you have an overflow in this basin, use that as the outfall.

Bill

[loretom]

Bill,

I have attached the spf file.  Like you suggested I changed the extension to .txt.

The retention basin has no outfall.  Here in bakersfiled we have basins that are supposed to hold the 100 year storm and percolate in 7 days.  There is no overflow.  They are designed with a watersurface that is 1-foot below the lowest catchbasin inlet elevation, so you have at least a 1-foot buffer.

I have seen more complex systems modeled with this program that have basins with no outfall and work fine.  Those were provided to us by the public agancy for coordination, so I can not share those files.

I think I must be doing somthing wrong here.

Thank you,

Miguel

[wfberry]

Miguel:

I am about the last person to try to help you on this.  I keep hoping that Fred would enter this discussion.

I ran your file and it ran just fine.  Unfortunately, I have no idea how your Retention basin should be set up.  Your program setup has a one hour  10 year storm that raised the basin up four feet.  Most of your pipes are surcharged but did not over top their inlets so I guess that is OK.

What kind of duration storm do your agencies require?

Bill

[loretom]

Bill,

The local agancy only requires a 10 year storm.  Things on the file seem to function because it has an outfall, but I would like to run it without the outfall.  In real life the sump has no outlet.  It is sized to hold a 100 year storm and percolate in 7 days.  I also tried it with a wier at the water surface elevation and it seems to work, but as I said this is not the true condition.

I can see if it was a detention basin, then this would work just fine with an outfall.

I can get the model to work with no sump and just an outfall.  This is what I did.  I will keep reviewing other files where they have managed to get the sump condition to work with no outfall.

Thank you,

Migul

[fcernst · Accepted solution]

.. I will keep reviewing other files where they have managed to get the sump condition to work with no outfall...

They are probably running the models with Kinematic Wave flow routing.

[loretom]

Fred,

Your are right.  That is what they did.

As far as you know is that the only way to do it if you don't want an outfall?

Thank you,

Miguel