(3) Shore the sides of the hole if there is a possibility that it will cave in. Use a barrel with
the head removed or a section of metal culvert pipe. As the earth is removed, force the shoring down.
The sharing can be removed easily and the cut edges bent over. Drill two holes near the top of the barrel
of culvert pipe to attach a winch line. Use this line to pull the barrel or culvert pipe from the hole.
b. Boring holes with an earth boring machine. Use the earth boring machine (Figure 1-2) to
bore holes up to 20 inches in diameter and up to 7 feet deep. When using this machine, proceed as
(1) Position the truck so the auger of the earth borer is directly over the hole location. Set the
truck brakes. Chock the truck wheels to prevent any shifting during the boring operation.
(2) Start the auger at a rotation speed of about 25 revolutions per minute. Control truck
engine speeds by signaling the truck operator. Bore until a depth of about 18 inches is reached.
(3) Raise the auger above the ground. Increase the auger speed to throw off the borings. The
nature of the soil can usually be determined by the first soil removed.
(4) Maintain a slow rotation speed when boring holes in sandstone, shale, or frozen ground.
Increase the auger rotation speed to about 125 revolutions per minute for average soil, sand, or clay.
(5) Bore 18 inches more. Raise the auger. Throw off the borings. Repeat this operation
until the hole is bored to its proper depth. Loose and remove by hand all large stones.
c. Waterjet method of setting poles. The waterjet method is used if caving soil or subsurface
water makes the use of other methods of hole digging impractical. Poles are set by the water jet method
(Figure 1-3) in the following manner:
(1) Dig the pole hole with shovels until the soil begins to cave in or until water is
encountered. The surface diameter of the hole must be 16 inches greater than the pole diameter at the
butt. Erect the pole in the hole. Use four people with pike poles to hold the pole erect.
(2) Lash a short pike pole to a fire hose and hose nozzle.
(3) Place the nozzle in the pole hole and turn on the water pressure. The water will gradually
undermine the pole and the pole will sink into place. Move the hose nozzle around the pole to prevent
the hose from being wedged as the pole sinks. A water pressure of approximately 25 pounds per square
inch is adequate. However, the quantity of water is more essential than high pressure. Ease off
carefully on the pike poles as the pole sinks.