AWWA D100 Overflow Weir Interpretation

[512Engineer]

AWWA D100 indicates:

"The overflow shall have a capacity at least equal to the specified inlet rate, with a
head above the lip of the overflow of not more than 12 in. (304 mm) for side-opening
overflows and not more than 6 in. (152 mm) for other types of overflows."

I can't find a technical definition of a "side-opening overflow". Is this just a sharp crested weir box inside of the tank, or does AWWA have another interpretation for this term? It doesn't appear be an industry term. For "other types of overflows", I'm assuming they are talking about Morning Glory Spillway type weirs/overflows?

I'd appreciate any guidance on what AWWA means with these terms. Thanks! Chuck

 

[Rubje]

Usually a side-opening overflow uses a weir or other type of opening that is located along the side of the tank, rather than at the top or bottom. The overflow may be designed to discharge water continuously, or it may be designed to discharge water only when the water level in the tank reaches a certain level.

As for your second question, I'm not sure

 

[georgeverghese]

There is also the V notch type over weir - this is a series of saw teeth cut into the weir. This reduces head over the weir lip at higher capacity, hence enables better turndown.