CONCRETE LINING FOR IRRIGATION CANALS. 
81 
THE LOS ANGELES AQUEDUCT, L*OS ANGELES, CAL. 
About 37 miles (196,402 feet) of canal forming part of this aque- 
duct is concrete lined. The excavation was made with a steam 
shovel, and some of the excavation was in very rocky ground. The 
slopes and bottom of the channel left rough by the steam shovel were 
brought to a fairly even surface by trimming off the high places, and 
the low portions were shoveled full of moist earth which was tamped 
to place. The guideboards set to allow a slab length of 12 feet were 
held to place by stakes driven into the earth. 
In placing the concrete for lining, a platform was built half wa}^ up 
the slope, and in order to reach the upper half of the slope the con- 
crete was handled a secoifd time from this platform. Alternate slabs 
were first laid and these were brought to surface by the use of a straight- 
edge supported on the guideboards. After this concrete had set and 
the forms were re- 
moved the interme- 
diate slabs were con- 
creted in and brought 
to a true surface, 
using the straight- 
edge on the hardened 
slabs as guides. A 
f-inch plaster coat 
of 1:2 mixture was 
finally applied. The bottom lining was afterwards laid continuous 
and with a curved bottom as shown in figure 15. The work in various 
stages of construction is shown in Plate XII, figures 1 and 2, and 
Plates XIII and XIV. 
This canal was designed to carry 923 second-feet of water at a mean 
velocity of 4.05 feet per second. The coefficient of friction n was 
taken at 0.014. 
No reinforcement was used, and on most of the work the lining is 
made of a concrete mixture having 1 part cement to 6 parts sand and 
gravel, but in some portions a 1:5 mixture was used. A blended 
mixture of one-half tufa and one-half hydraulic cement was used for 
all the lining. The total cost of the concrete per cubic yard in place 
was about $5, and the materials used in a cubic yard of concrete cost 
about as follows: Cement, $2.60; sand and gravel, $1; and mixing 
and placing, $1. 
RIDENBAUGH CANAL, BOISE, IDAHO. 
The 2-mile portion of this canal which is concrete lined is along a 
gravelly sidehill that had formerly caused large seepage losses and 
expensive maintenance. 
48307°— Bull. 126—14 6 
Fig. 15. — Cross section of concrete-lined channel, Los Angeles Aque- 
duct, Los Angeles, Cal. 
