26 
BULLETIN 190, IT. S. DEPARTMENT OP AGRICULTURE. 
driven by means of a heavy maul and may be removed by a three- 
legged derrick and a special grabhook, as shown in the figure. 
If the soil in the bottom of the completed trench be so soft that it 
will not support a man's weight, boards should be laid under the tile 
to keep them in line and on grade. For large-sized tile the planks 
should be built into a triangular trough ; or, if conditions are exceed- 
ingly bad, piles should be driven and planks secured to them in the 
form of a cradle. Under such conditions it is often advisable to 
employ sewer pipe in place of drain tile, as the bells aid in keeping 
the line intact. Second-quality pipe is suitable and may generally 
be purchased at about 
Cottonwood Maui & ^V^"!^* ■ the same cost as drain 
tile. Under ordinary 
conditions, however, 
the use of sewer sec- 
onds is not recom- 
mended, as the cost 
of freight and haul- 
ing is higher than for 
drain tile and the 
former are heavier 
and more difficult to 
handle. Also in sta- 
ble ground it is nec- 
essary to dig out 
places for the bells, 
which cons iderably 
increases the cost of 
trenching. 
The tile should be 
hauled and distribut- 
ed in one operation 
and should be strung 
out end to end in a 
line about 10 feet to one side of the proposed trench, with an occa- 
sional length laid down to allow for breakage. 
Lines and grades for drainage work should be carefully established 
by surveys. To obtain a guide for hand trenching, a cord or wire 
should be stretched along the ground at one edge of the proposed 
trench, and to afford a convenient method of determining the proper 
depth at all points grade planks should be set up at each 50-foot sta- 
tion, as shown in figure 21. These planks should all be of the same 
height above the proposed grade of the trench, so that a cord stretched 
over the center of the trench will be at a uniform height above grade. 
Fig. 
20.— Method of sheeting trenches of moderate depth (Miller 
system). 
