192 SEWER DESIGN 



cubic feet per second, or the amount of run-off to be cared for 

 by the drain at that point. It may be noted here that on steep 

 hillsides 5 to 10 per cent is sometimes added, but as this area 

 is entirely unimproved and likely to remain so, having a large 

 proportion of lawn and no paved streets, nothing need be 

 added. 



By diagram on Plate 3, to discharge 18.8 cubic feet per 

 second on a grade of 10 per cent, which the hill from this 

 point down is seen to be, will take a 15 -inch pipe, which will 

 run to Spring Street. Here an area of 540,950 square feet, 

 or 12.4 acres, discharging 25.3 per cent, adds 10.0 cubic feet 

 per second. Since the diagram does not show the intersection 

 of the 30 cubic-foot line with the 10 per cent grade line, the 

 size must be computed. It is found to be an 1 8-inch pipe. 

 At the foot of the hill, 400 feet from Aurora Street, the grade 

 changes to 0.5 per cent, and on this grade a 3O-inch pipe is 

 required, which will run the 400 feet to the corner. Here the 

 drainage of 7 acres, or 5.6 cubic feet per second, enters, making 

 34.4 cubic feet in all. On the same grade of 0.5 per cent this 

 takes about a 33-inch pipe. At Seneca Street will enter the 

 water from the area between Seneca and State streets and west 

 of Stewart Avenue. This amounts to 11.2 cubic feet per 

 second, making 45.6 in all, requiring a 39-inch pipe. This 

 may be taken from the diagram on Plate 4 and will be either 

 brick or concrete. At Buffalo Street the contributing area 

 is 13.7 acres, or 10.9 cubic feet per second, making a total of 

 56.7 cubic feet, requiring a 42-inch sewer. On account of 

 the amount of sediment brought down the hill, and the large 

 deposits where the velocity is so retarded, it will be wise to 

 increase the size from here to the creek, making it 48 inches 

 for the remaining distance. 



Reviewing the velocities, the farthest point is at the corner 

 of Quarry and Buffalo streets. From here to State Street, 

 with a grade of 6 per cent, the water flowing in an open 

 gutter will have a velocity of about 9 feet per second, requir- 

 ing, for the 1085 feet, 120 seconds or 2 minutes. Still flowing 



