Underground Detention

[mdriver1]

I have modeled an underground detention system utilizing a 40' x 250' area and all is fine modeling/outlet/diversion control but the reviewer is asking to demonstrate that at least 50% of the parking spaces be inundated if underground system fails. This particular system is solid storage piping (non-arch chamber and no infiltration into surrounding stone/soil).

Kind of understand the logic for asking but how to model in HydroCAD???

My thoughts:
create a pond representing the area and volume for the parking lot surface. pretty flat based on other requirements.
then route the respective post drainage basins to the surface pond peak elevation to plot.

Anyone else hear of such a request and have modeled it?

Thanks,
mdriver1

 

[psmart]

I could understand concerns about the potential failure of an infiltration system, but I don't see how a system of "solid" chambers could fail (other than getting filled completely with sediment.)

Anyway, your approach seems correct: Model the system using only storage in the parking lot, ignoring the chambers.


Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[mdriver1]

Hi Peter,
Yes sir. I agree. I'm just beginning to explain my design to the reviewer but it's in his mind infiltration and chambers!
It's clearly identified in my hydrology report using solid piping.
My client hasn't made up his mind whether to go with pavers and/or chambers w/infiltration.
In the spirit of the typical fast paced submittal world we live in, I chose to model solid hdpe pipes with headers until further notice.

Modelling in this manner seemed logical. Thanks for confirming!

Mark H. Driver, PE, PLS
Landmark Engineers & Surveyors, LLC

http://www.landmarkesllc.com

mdriver@landmarkesllc.com
(865) 776-9074