92 SEWER DESIGN 



Before considering the relation between the amount of water 

 finally determined on and the resulting size of the sewer, other 

 sources of sewage are to be considered. 



PROBLEMS 



30. Show that by changing 6.8 to 8 in the Hawksley formula, the 



A 3 



value of D 10 becomes .001615. 



o 



31. Show that the numerical value of the constant in the Biirkli-Ziegler 

 formula is changed from 0.60 to 4.23 by substituting English units of 

 measure. 



32. Taking the five formulae of p. 85, plot curves for each equation, 

 taking areas up to 1000 acres for abscissae and run-off in cubic feet per 

 second per acre for ordinates. 



33. Determine the probable run-off from some definite district or 

 area. Use all the methods and compare results and make a final decision 

 in the light of all the evidence. 



34. Show by numerical explanation how the constant of a formula 

 representing the method of Chapter V, viz., Q = C-vA can be reconciled 

 with the constants of Chapter VI. 



35. Show by a diagram how much effect the term S' 25 has in the math- 

 ematical formula, that is, plot two curves with run-off per second per 

 acre for ordinates, and values of S for abscissae, with A = 500, and = 50 

 acres, and with assumed values of C and r. 



36. Plot curves from the 5 formulae of p. 85, with run-offs as ordinates 

 and areas as abscissae in order to show the effect of the exponent of A. 

 Take a fixed value for C-r, and the values of S, i.e., 5" = .ooi, 5" = .005 and 

 S = .05. 



