How is design storm interval determined? I looked into the LEED BD+C Reference Guide on page 97 in the example (last calculation) at the top of the page. From where do the 3 days / 72 hrs come?
I have an infiltration pond and it can hold the volume that is calculated, but it needs to be emptied before the next storm arrives. Is 3 days a default value or how can I determine the time to use between two storms? The actual project is in Warszawa, Poland.
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Amy Rider
Sustainability ManagerKEMA Services
161 thumbs up
August 31, 2012 - 6:46 pm
Therese,
The days is not a default value, but an example from the Maryland Stormwater Design Manual.
Also in this manual is this definition, "The detention lag time (T) for the one-year storm is defined as the interval between the center of mass of the inflow hydrograph and the center of mass of the outflow hydrograph." (p. 48). Does that help?
Sandro Tubertini
ChapmanBDSPJanuary 20, 2014 - 1:32 pm
Dear Amy and Therese,
Considering that we are using the ACP to calculate the reduction of the volume of stormwater runoff, what should be the time interval we have to use? Bare in mind that we are in a tropical zone and the average 30% rainfall in the month with highest average rainfall is over 70 mm.
Thanks a lot.
Michael DeVuono
Regional Stormwater LeaderArcadis North America
LEEDuser Expert
187 thumbs up
January 20, 2014 - 2:06 pm
Time interval refers to the spacing (time) between points used to plot a hydrograph. But I do not think this is what you are referring to?
Are you trying to develop a percentil storm using local rainfall data?
Sandro Tubertini
ChapmanBDSPJanuary 20, 2014 - 2:57 pm
Hi Michael,
Thanks for your prompt reply.
Our understanding is that this credit requires a diminishing in the volume of water sent to the city rainwater drainage system (in this case this is achieved by a reduction on the flow).
The sizing of this retention tank, based on the number above is becoming massive and therefore we are trying to understand if we should consider the volume of run for one hour our smaller interval.
Also if we decide to discard the water, when and how long should I take to do that?
Best
Michael DeVuono
Regional Stormwater LeaderArcadis North America
LEEDuser Expert
187 thumbs up
January 20, 2014 - 4:12 pm
The time interval in this equation refers to the interval between design storms.
So: If you are designing for 1-year storm 31,536,000 seconds. Divide the volume of your tank by that to determine the minimum drawdown rate. Then you need to design an orifice Q=C(2gh)^1/2 that meets that rate.
See the SSc 6.1 forum for a more detailed discussion of this.
http://www.leeduser.com/credit/NC-2009/SSc6.1