Outlet Control Structures (square vs. circular)
Outlet Control Structures (square vs. circular)
(OP)
I have an outlet control structure in a standard detention pond that I specified as a square concrete shape. I was told that most engineers use ciruclar due to cost, also how well it holds on to an earth pond embankment... is this correct?, and is this a better shape when placing the outlet in an earthen pond embankment?





RE: Outlet Control Structures (square vs. circular)
does your outfall structure contain multiple stage weirs or orifices?
does the design call for the structure to be cast-in-place or pre-cast?
how large of a structure are we talking about here (height and width/diameter)?
I have been working with storm water design for several years now and have never specified a circular outfall structure. I have seen ponds overdesigned and their discharge limited by one outfall pipe, without a structure.
The structures I typical specify have to control the release of multiple storm events and therefore typically have multiple weirs and/or orifices. They are also specified as cast-in-place due to the complexity of the weir/orifice structures and the size of the units. I recently specified a polygonal outfall structure with the largest face containing the primary orifice and the multiple orifice system. It was approximately 30' wide, 12' deep, and 12' tall made of 8" thick reinforced concrete.
If your system requires only a single orifice (and possibly an open top of structure) I see no problem specifying a circular structure. I would count this as the exception rather than the rule.
Nate
RE: Outlet Control Structures (square vs. circular)
I'm not sure I know what you mean by "how well it holds on to an earth pond embankment..."
RE: Outlet Control Structures (square vs. circular)
Most of our structures, i believe are precast... say 4' x 4' inside diameter, no more than 12-14 feet tall. Mine is 16 in this case.
RE: Outlet Control Structures (square vs. circular)
RE: Outlet Control Structures (square vs. circular)
See http://ww
B-10.40 and B-10.60
Large projects often require custom structures, which could be cast-in-place or precast vaults with internal weirs, baffles, orifices added.
RE: Outlet Control Structures (square vs. circular)
Just remember the poor guys that have to construct the forms. And also be nice to yourself and make you orifice or weir calculations easier on you with the simplest shape you can get away with (ie circles or squares).