72 BULLETIN 852, TJ. S. DEPARTMENT OF AGRICULTURE. 



puted, from which other similar chutes could be designed from a 

 capacity standpoint without regard to the actual velocity attained. 

 However, we do know, from experiments made on open-channel 

 concrete chutes, that the value of n in the Kutter formula must be 

 raised 0.002 to 0.004 when a chute is designed from a capacity 

 standpoint. 1 In other words, the series of experiments on this 10-inch 

 pipe chute indicates that a value of n of about 0.014 or 0.015 should 

 be used in designing for capacity, instead of the values as shown in 

 Table 11, namely, about 0.0119. 



A view of one of these pipe chutes, in course of construction, and 

 showing the vertical curve mentioned above, is given on Plate 

 XXVIII in Volume II of Prof. Etcheverry's work. The writer 

 believes this view is of the 10-inch chute discussed above. 



No. 52, Experiment S-41. — 36-inch jointed concrete flow line, 

 Colorado Power Co., near Nederland, Colo. — In 1909 a flow-line 

 conduit 12 miles in length was laid down the canyon of Middle 

 Boulder Creek from the dam at Barker Reservoir to a small reservoir 

 about 4 miles from Boulder, Colo., and about 2,000 feet in elevation 

 above the creek bottom, where one of the plants of the Colorado 

 Power Co. is located. This conduit is laid on an even gradient of 5 feet 

 per 1,000 feet of pipe, except where inverted siphons are required 

 to cross gulches and draws leading into the canyon. An article 

 describing this installation says: 2 



The 3-inch shell of the pipe that is laid on the hydraulic grade consists of one part 

 Portland cement and three parts aggregate, graded from sand to stones having a 

 maximum dimension of 1 inch. The pipe was cast in sections 2 feet long, with 

 socket on one end and a bevel on the other end of each section to form the joints. 

 Each section contains two hoops of No. 5 steel wire having a high tensile strength, 

 one hoop being placed 6 inches from each end. These" hoops are not considered to 

 be of much value as reinforcing, but rather as an aid in preventing breakage before 

 the concrete has set. The line of the conduit is very crooked, the longest tangent 

 not exceeding 500 feet. Straight and beveled pipe were employed together to build 

 the conduit on curves. The latter were located so their radii were as nearly uniform 

 as possible, requiring only two kinds of beveled pipe. 



The mixture was placed in rather dry layers 3 inches thick and 

 carefully tamped. This allowed the forms to be pulled immediately 

 after which the pipe section was kept thoroughly wet for 7 days, then 



the inner surface of the the sections was coated with a thick wash of neat cement to 

 fill all irregularities. This surface was thus finished quite smooth, and, with the 

 manner in which the joints were made, produced a conduit having a large carrying 

 capacity. 



During the season of 1915 the writer conducted a series of experi- 

 ments upon the carrying capacity of a portion of this conduit near 

 the upper end. A reach 1,977 feet long was chosen. Open stand- 



Eipes near each end of the reach and approximately each 500 feet 

 etween the ends gave opportunity for measurement of the pipe 

 segment not occupied by the water at five evenly spaced stations on 

 the reach. For each run the quantity of water flowing in the pipe 

 was varied by regulation of the outlet gates of Barker Reservoir. 

 The velocity of the water in the flow line was determined by accepting 



i The fact that the fundamental hydraulic equation Q = A Fdoes not hold for chute drops, where high 

 velocities, wave action, and turbulence exist, was first called to the attention of the writer by Mr. W. G. 

 Steward, of the United States Reclamation Service. The results of his experiments, which have been 

 corroborated in essentials by those of the writer, are found in Irrigation Practice and Engineering, by 

 B. A. Etcheverrv, Vol. Ill, p. 261. 



2 Engin. Rec.,'Nov. 6, 1909, vol. 60, p. 514. 



