JOB LAYOUT

Many excavation jobs are small and routine. Other jobs may be quite extensive. On small jobs, you will normally be shown where to dig and to what depth you must dig. On larger jobs, you maybe shown the plan of the proposed ditches. Grade stakes on the projects are marked to indicate to what depth the ditches must be excavated. (Chapter 15 covers grade stakes in detail.)

NOTE: Before starting any excavation, you must ensure a valid digging permit is present that covers the area you are tasked to excavate.

When arriving at the project site, you may notice two rows of grade stakes: one row on the center line of the proposed ditch and the other row offset a given distance from the center line. Do not disturb the offset stakes. They are the stakes you will follow while excavating the ditch that have information relative to the depth of the excavation written on the side.

Figure 9-62.-Measuring the depth of a ditch.

As a guideline, you can use a string drawn taut from the first centerline stake to the following centerline stakes for a distance of several hundred feet ahead of the machine. Then spray paint over the string with a bright-colored paint that will mark the ground to be excavated. With the bucket centered over the first centerline stake, you will be able to excavate the painted line. If you get off center, you can bring the backhoe back into alignment gradually by steering the machine in the desired direction.

Check your grade (ditch depth) frequently. You can do this by using a straight board, a carpenter's level, and a measuring stick or tape measure. Align the corner bottom of the horizontal board on the crowfoot cut, marking of the offset stake. Place the level on the horizontal board and adjust the board opposite the stake until the level indicates the board is level. Measure from the bottom edge of the board to the bottom of the ditch, as shown in figure 9-62. This measurement should correspond to the amount of cut indicated on the stake. All of the stakes will be cut stakes. You should always try to excavate to the depth specified on the stakes.

NOTE: It is better to excavate an inch or two below grade than not excavate deep enough.

FOUNDATION EXCAVATION

The backhoe is used to make excavations for basements or any other square- or rectangular-shaped job. It is also used extensively for digging wide trenches for laying water and sewer pipe. When the backhoe is used for the digging of square- or rectangular-shaped jobs, the procedures may vary with the shape of the job, restrictions caused by surrounding buildings, or special requirements for disposal of the spoil. In all cases, the starting point and digging sequence must be planned, so the backhoe conveniently works itself out into the clear. Improper procedures will not only trap the machine, but can lead to situations where the machine cannot be positioned to complete the job. In this situation, hand digging may be required to complete the excavation.

An accepted starting and digging sequence that can be followed for excavating a small foundation is shown in figure 9-63. Remember that digging time is lost each

Figure 9-63.-Foundation excavation.

time the machine must be moved. The digging sequence is planned, so a maximum amount of spoil can be excavated before the machine is moved to the next position.

For example, the first cut is to be made on the west line (fig. 9-63, view A). The starting position of the machine would be on the west line at a point where the boom and dipper stick will reach the northwest corner. The machine and boom are lined up parallel with the west cutting line, so the outer edge of the bucket is exactly in line with the cutting line.

The first cut is made by digging a ditch along the west cutting line. The ditch should be dug to its full depth and grade. This depth and grade serves as a depth guide for the other cuts. When the west wall has been dug as close as possible to the machine position, you then swing the boom to reach near the center of the north cutting line. The second cut, as shown in figure 9-63, view A, is made by digging a trench back from the north wall. The material cut in the angle formed between these two trenches is removed in layers until the bottom grade is reached.

NOTE: Ensure that the desired grade is reached before moving the backhoe.

The backhoe is then backed up into the second position, as shown in figure 9-63, view B. Digging is continued in steps, as shown in figure 9-63, view A. The ditch is dug first along the west line. The boom is then swung around to cut the angle trench and the material is removed to grade. Digging is continued in this manner until the south line is reached.

The backhoe is then moved to the unexcavated portion of the south line. This position is shown in figure 9-63, view C. Here, the backhoe is positioned with the bucket in the excavation at the southwest corner to begin the ditch along the south cutting line. Again, after the ditch is dug along the cutting line, you should swing the boom toward the center to remove as much spoil as possible from this machine position.

You should continue to move the backhoe around the excavation, repeating the digging steps until all four cutting lines are cut and the spoil removed. To make the final cut to remove the material, you may have to position the machine at the edge so the bucket can dig straight up. This cannot be done unless the soil type is known to have good-bearing qualities. Cave-ins will result if the soil will not support the weight of the machine.

NOTE: Before excavating at a jobsite, always consult with the project supervisor or crew leader about your excavation plans. Keep in mind that the area you might be placing the spoil material might be an area for other construction tasking. Excavating at a jobsite must be a well-thought-out plan.

SAFETY

Safety precautions that apply when you operate front-end loaders, backhoes, and excavators are as follows:

. Clear the immediate area of personnel or obstructions before starting the engine.

. Keep the bucket as close to ground level as possible when transporting loads on grades or slopes.

. Never operate any control from any position except in the operator's seat.

. Be extra careful when working on banks or hillsides.

. Always keep the machine in gear when going down steep grades. Never coast or freewheel.

. Drive at speeds slow enough to ensure safety and complete control especially over rough terrain.

. Reduce speed when making turns or applying brakes.

. Always lower the lift arms or boom to the ground or block them securely before performing any service or when leaving the machine unattended.

. Never dismount the loader, backhoe, or excavator when it is in motion.

. Never permit anyone to ride on the equipment.

. Do not oil, lubricate, or make adjustments when the engine is running or the bucket is raised and unblocked.

. Never refuel when the engine is running.

. Do NOT smoke when refueling.

. Never operate in a closed area; provide proper ventilation.

. Do not wear loose fitting clothing which may catch in moving parts.

. Always wear seat belts, steel toe safety shoes, hard hats, gloves, and other required personal protective equipment.