SEWER CROSS-SECTIONS 



211 



Metropolitan sewerage systems, by Howard Carson, Chief 

 Engineer. 



While the circular section is always employed for terra 

 cotta pipe, in the case of larger sewers, made of brick or concrete, 

 there is not the same necessity for adhering to the circular 

 section. It is sometimes economical not to do so and a large 

 number of peculiar and interesting sections may be found by 

 reference to the larger text books and to the files of the periodi- 

 cals. A floor of nearly flat area saves on the cost of forms. 



1.0 



0.9 



0.6 



"S0.3 



0.2 



0.1 



0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 L2 



Proportional Velocities and Discharges 



FlG. 60. 



these floors being laid very much like sidewalks. Then, in firm 

 earth where good lateral support may be had, light sidewalls 

 can carry an arch cover at the minimum of expense. In deep 

 cuttings, sometimes elliptical or oval sewers have been used 

 with a view of saving excavation by limiting the width of the 

 trench. Where, in other places insufficient head room has 

 been encountered, the circular form has been changed to an 

 ellipse with the long axis horizontal or to a section having very 

 short sidewalls and with flat arcs for the top and bottom. 



It is not possible in these pages to take up in detail the 



