How Big Is That Overflow?

How Big Is That Overflow?

When you see a manhole gushing, how do you estimate the size of the overflow? The Southern Section Collection Systems Committee, a part of the California Water Environment Federation, is offering collection system operators in that state a simple visual tool for estimating (see photos).

These handy rulers picture manhole overflows gauged at various flow rates in gallons per minute (gpm). The intent is to help collection personnel accurately determine the severity of overflows they encounter in the field.

For years, says SSCSC representative Jim Aanderud, collection personnel have been using pictures from overflow simulations taken 12 to 15 years ago. “For various reasons, those pictures were not great,” he says. “SSCSC decided to re-shoot these pictures at a local water district.

“The pictures start at 5 gpm and go up to 400 gpm. What’s different about them is that we include not only a close-up of the water spilling out of the manhole, but also a picture showing the surrounding wet area.

“Our intent is for every collection person in California to have one of these rulers so they can better gauge the quantity of water coming out of a manhole during a sewer overflow. The estimating of quantity is very important, because that is what is reported to the EPA, and fines are levied according to the number of gallons released.” The SSCSC is printing 8,000 to 10,000 rulers to be handed out to collection system personnel.


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