Storm Water Attenuation design parameters

[pba]

Here is a philosophical question:

We have a new building to be constructed on a site where the storm water run off will discharge through an attenuation facility. After periods of heavy rain the tank will be full of water and will take about two days to empty. The location has quite high annual rainfall.

There is a risk of fire within the building and a sprinkler system is to be installed. If there is a fire the fire water will enter the attenuation tank which will be automatically sealed to prevent outfall. The tank is sufficient to hold the total amount of fire water.

Now we have established a method of draining the tank down during a fire so this problem did not effect the design, but how much storm water, if any, should we consider to be present in the tank during a fire event?

 

[SlideRuleEra]

20% of capacity. Since there is no way of knowing, this seems like a good time to use Pareto's Principle, the 80-20 rule. There are two advantages:

1. You will have some provision for stormwater in the system.

2. Because of the established psychology of the 80-20 rule, the above assumption will be accepted as "reasonable" by many people.

Here is a link on the history of Pareto's Principle

http://management.about.com/cs/generalmanagement/a/Pareto081202.htm

http://www.SlideRuleEra.net

 

[bimr]

Take the probablility of rain each day and then multiply it by twice the average daily rainfall. If you then subtract the drainage volume over 2 days, that would give you the residual amount in the basin.

 

[ACtrafficengr]

Put a dry hydrant in the basin, so the fire department can recycle the sprinkler water!

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