16 BULLETIN 1408, U. S. DEPARTMENT OF AGRICULTURE 
used an opening is left under the floor through which water is very 
likely to pass even though good cut-off walls have been installed. 
Some engineers build these structures without foundations with the 
expectation that they will settle somewhat. The sluiceways are 
designed to withstand the strain of such movement, and an effort 
is made to weight them so that the settlement will be uniform. This 
method appears to be satisfactory. 
Cut-off walls are an important part of all such structures. Not 
less than two lines should extend crosswise under the bottom, up 
the sides and well out along the line of levee. Where piles are not 
employed care should be used that portions of the cut-off walls do 
not reach into firmer material and prevent uneven settlement; it 
may be necessary to depend upon a greater number of lines of short- 
length sheet piling. Head walls and cut-off walls are equally nec- 
essary where pipe is used for conduits. 
Iron tide gates, machined to provide close seating, in many cases 
have been highly satisfactory. Where chemicals in the water may 
corrode iron, bronze or wooden gates should be installed. Wood 
gates have had wide use and where properly constructed and con- 
tinuously submerged have given excellent service. Figure 12 shows 
a wooden flap valve made up of a double thickness of 2-inch mate- 
rial cross lapped and well bolted together, with an angle iron frame 
on the outside. Three-inch material embedded in concrete forms 
the seat. This particular gate is suspended from two trolley rails, 
which readily permit it to move outward. This gate will operate 
under very low heads and was designed especially for districts in 
the vicinity of Portland, Oreg. 
Many types of hinges have been designed to meet particular con- 
ditions. A short single-pin hinge is not desirable; better balance 
and action will be obtained from a double-pin hinge connected with 
a long link or hanger bar and fastened to the gate about one-third 
the distance from the top. The lower part of the gate should be 
arranged so that weights can be attached or removed readily, and 
adjustments made after the gate is in place so that it will operate 
under a very low head. The seat should incline from the vertical 
slightly, but not more than 18°, so that the gate will seat tightly at 
low water. Careful and accurate construction should insure this. 
Plate 2, A shows the land end of a reinforced concrete sluiceway. 
This particular structure has a superimposed culvert and a platform 
on the interior end to provide for the installation of an electrically 
driven chain-lift pump the use of which may be required occasionally 
when the gravity discharge is not sufficient. 
Where tidal range permits and much water is to be passed, sluice- 
ways with wide gates hinged at, the side are used. These gates are 
the so-called " barn-door " type which has had successful use in cer- 
tain sections of the Southeast. The bearings supporting the gate 
should be bronze or some other noncorrosive material. The frame 
should be wood, which best absorbs the shock occurring when the 
gates close against each other. The gate panels may be steel as in 
Plate 2, B. When closed the gates should be at an angle of from 18° 
to 23° with a line connecting their points of support. The bottom 
of each gate fits against an offset on the concrete floor of the 
structure. 
