SEWERAGE 



Egg-shaped sewers have a larger hydraulic radius than cir- 

 cular sewers when the flow is shallow; consequently, they 

 reduce the likelihood of deposits. The general form of the 

 cross-section of an egg-shaped sewer is shown in the accompany- 

 ing illustration. The part above the line OO' is a semicircle, 

 the part below the line OO' is 

 formed by the three arcs DE, 

 EG and GA , the arcs DE and 

 GA having equal radii. It will 

 be noticed that three different 

 radii are used in constructing 

 the figure; namely, CA = CB 

 = CD = r for the upper semi- 

 circle, OD = OE = O'G = O'A 

 = r\ for the two side arcs DE 

 and GA, and C'E = C'F = C'G 

 = ro for the lower arc EFG, commonly called the invert. 



The proportions of the different dimensions, as well as other 

 useful data, are given in the accompanying table, and the dis- 

 charge and velocities for various grades in the preceding table. 



ELEMENTS OF CROSS-SECTION OF EGG-SHAPED 

 SEWERS 





