Re: Storm Water Pumping

In article <[EMAIL PROTECTED]>  David King says...
> In my location, Vancouver, Canada, the most common (and only as far as I am
> aware) form of stormwater pumping is in low lying areas adjacent to the
> dyked Fraser River, where storm pumps kick in to pump urban run off into a
> river that is high due to snow melt or tidal effects - in less extreme
> circumstances the runoff is carried through the dykes by culverts  equipped
> with a flap gate.
> 
> Does anyone have any examples, good or bad, of storm water pumping in lieu
> of a gravity system?
> 

David:

Are you looking for requirements for large scale pumping or the smaller 
scale pumping sometimes required in urban areas?  As you probably know 
Seattle faces this problem when a house is built on the downhill side of 
a street when the sewer (usually a combined sewer) is fairly shallow in 
the street above the house.  In this case it is often required that both 
sanitary and storm must be pumped up to the street.

The City of Seattle requires that the rate of discharge from a property 
be no more than 0.2 CFS/Acre for 25-year, 24 hour storm, 0.15 CFS/Acre 
for 2-year, 24-hour storm, or 0.5 CFS/Acre for a 100-year, 24-hour 
storm.  In general, a pumped system must be able to handle the 100-year, 
24-hour event.  

>From the above you can see that a pumped system will require a fairly 
large detention tank or vault in order to handle the 100-year event with 
a maximum discharge rate of 0.5 CFS/Acre.

When designing these types of systems I have always specified a duplex 
pump system so that if one pump fails you at least get some action.  
However, in most cases it is necessary to add a throttle valve to reduce 
the discharge rate to meet the required max allowed discharge.

-- 
Bob Morrison
R.L. Morrison Engineering Co.
Structural and Civil Engineering
Poulsbo WA