SEWERAGE 



Capacity Required for Storm- Water Sewer. Various for- 

 mulas are used for the capacities of storm-water sewers. Of 

 these the formula proposed by Buerkli, a German authority, 

 is probably the most reliable. It is as follows: 



E=fre, 



in which e= \SA 3 and is tabulated in the accompanying table. 

 Im these formulas, E is the total flow in cubic feet per second 

 from a sewer district containing A acres ; 5, the average surface 

 slope (presumably toward and along the drain), in ieet per 

 thousand feet through drainage district; /, a coefficient relating 

 to "the proportion of rainfall that will reach the sewer"; r, the 

 coefficient representing rate of rainfall, in inches per hour, 

 "during period of greatest intensity of rain. " 



VALUES OF . OR 



To the coefficient / in the Buerkli formula are given values 

 ranging from .31 in rural districts and suburbs to .75 in cities 

 well built up, with a mean value of .62. By mean value is 

 here meant that value which best represents the most usual 

 conditions. 

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