AutoCAD Civil 3D - Stormwater

[#1]

I have set up a portion of my system as follows:  I have a junction where I enter my external flow which flows to a storage node.  From the storage node are two pumps, each with their own respective lag & lead starts and stop heights.  My problem with surcharge and flooding always occurs in the junction just following the pumps that are then followed by a single 3" forcemain (approx 4000 ft long with a -0.001 ft/ft slope).  What is a simple fix to this problem?

Matthew Dillman

NIES Engineering, Inc.

[#2]

Also, just noticed that only one of the pumps was working.  Any other ideas why the other wouldn't kick on?  The controls are: Pump 1 - on @ 6 ft, off at 3 ft; Pump 2 - on at 6.75 ft, off @ 3 ft.

[#3]

I haven't used the pumps function at all, I just have a few thoughts.

What type of link are you using to connect the junction and the storage node?

Is there a reason you can't enter your external inflows at the storage node instead of at the junction?

Is there an option to increase or decrease the time step when using pumps?

There might be an issue with the junction surcharging before allowing the flow to get to your storage node. By decreasing the time step it might even the flow calculations out.

Let me know if any of that helps.

Ryan

[#4]

I haven't used it in SSA yet, but  in EPA SWMM you can set a max surcharge depth before flooding at junctions to simulate bolted/sealed manhole covers.. Then you can see how high the HGL can go.

SSA has a surcharge setting for junctions.

[#5]

rdbrennan:

- I'm connecting the sotrage to the junction via pump link.

- SSA will not allow external flows directly to storage.

- Cannot increase or decrese time steps on pumps; they are based on real time data (pump curves, start and stop heights, etc).

fcernst:

- I set my surcharge elevation to an exaggerated 10,000 ft and there were still all sorts of problems.  (I read somewhere that if you did this it'll eliminate flooding problems; apparently not the case).

- I'm trying to simulate real time flow and there is never actual surcharge problems at this storage tank.

All-in-all, I'm trying to calibrate this model based on real time DWF data I already have.

Many thanks!

Matt 

[#6]

"- SSA will not allow external flows directly to storage."

• I see External inflows here under flow properties.
• I'm sure he meant try taking your Routing time step down to 1 second for stability.

[#7]

I didn't even notice that! Thanks.  And my routing time is at 1 second.

[#8]

Would it be possible to attach a model, I would be interested in looking at it.

[#9]

Here you go.