62 BULLETIN 126, U. S. DEPARTMENT OF AGRICULTURE. 
EAST CONTRA COSTA IRRIGATION PROJECT, BRENTWOOD, CAL. 
This enterprise, although much larger, is similar in design, purpose, 
and scope to that at Patterson. Mr. A. Kempkey, the engineer in 
charge, in writing of this project claims that some improvements 
have been introduced in the lining as planned over the lining used 
on the Patterson project. One of these is the insertion of two expan- 
sion joints at the toe of each slope and parallel to the canal axis. It 
is also proposed to apply the mortar coat by means of a cement gun 
at an estimated cost of 1 cent per square foot of surface. 
The expansion joint used on both projects is shown in detail in 
figure 5, page 60. It has given good satisfaction wherever used in 
both canal and reservoir lining. A medium grade of asphalt, applied 
warm enough to flow readily but not smoking hot, is considered best 
to fill the joints. In using this joint it is not necessary to place the 
lining in alternate sections, as a tapering strip of wood may be in- 
serted between adjoining sections. These strips can be afterwards 
removed and the joints formed by pouring asphalt into the grooves 
and applying a |-inch coat of plaster on top of the asphalt. Plate 
III, figure 1, shows the work of lining this canal in progress and in 
Plate III, figure 2, is shown a portion of the completed canal lining. 
NORTH SIDE TWIN FALLS LAND & WATER CO., MILNER, IDAHO. 
This company lined 8,400 feet of its main canal to increase its 
capacity. The canal is carried for several hundred feet along a 
rough lava rock cliff and is 60 feet above low water in the river. The 
outer bank through this section is a concrete retaining wall. The 
remainder of the lined section is excavated almost wholly in solid 
lava. The grade varies from 0.001 in narrow places to 0.0002 and 
0.00025 in the wider sections. 
The canal was emptied October 10, 1909, and the work of preparing 
it for the concrete was commenced as soon as the channel had dried 
sufficiently. In places for several hundred feet from the headgates 
the canal bed was considerably below grade. The rock projecting 
into the canal section in the sides and bottom was blasted and 
smoothed, the low places being filled to subgrade with broken stone 
and puddled earth. 
An 8-inch thickness of concrete was applied to the sides of the 
rock sections and a 6-inch thickness to the bottom. The sides of 
the rougher rock sections were riprapped to secure a better align- 
ment and to save concrete. Cavities and large irregularities were 
back-filled with stones and puddled earth. It seems to the writer 
that the 6-inch thickness laid on the bottom of rock sections might 
have been reduced to 3 or 4 inches if the bed had been better pre- 
pared by the placing of finely crushed stone, compressing this mate- 
rial by rolling to secure an even surface and uniform grade, as is done 
in macadamized road construction. 
