Finish Grade Stakes

When performing final grading, you are likely to work with stakes called blue tops. These are hub stakes, which are usually 2 inches by 2 inches by 6 inches. These hubs are driven into the ground until the top is at the exact elevation of the finished grade as determined by the surveying crew. They are colored with a blue lumber crayon (keel) to identify them as finish grade stakes. Red crayon is normally used to indicate the subgrade elevation. Blue top stakes are placed when the existing grade is within 0.2 feet (2.4 inches) above the final or desired grade. The desired grade is obtained by lowering or raising the compacted grade with a grader until it is flush or even with the top of the hub (fig. 15-36).

Figure 15-35.-Right-of-way stake symbol.

Figure 15-34.-Slope stake set in existing natural groundline.

LEVELING EQUIPMENT

To set, use, and compute grade stake measurements, you must be able to measure the vertical distance from one point to another. This process is called leveling and is accomplished by using leveling equipment.

A level is an instrument used for measuring vertical distances. All levels have a line of sight with a bubble device for maintaining the instrument in a _{horizontal plane.} Levels vary in their accuracy

Figure _15-36.-Finish grade stake.

according to the quality and magnification power of the lens.

Vertical distances are actually measured by sighting on a graduated rod, called a level rod. Like other surveying equipment used for measuring distances, level rods usually are graduated in feet, tenths, and hundredths.

HAND LEVEL

The hand level is generally a round metal tube about 6 inches long with an eyepiece at one end, a cross hair at the other end, and a level vial on top (fig. 15-37). Part of the cross-hair end is covered with a mirror that reflects the image of the bubble to the viewer.

To use the hand level, look through the eyepiece end at the rod with the level vial on top. Tilt the entire hand level until the bubble is centered on the cross hair while looking through the eyepiece. It is sometimes necessary to know the height of the level above the ground where you are standing. This may be accomplished by resting the level on a stick of known

Figure 15-37.-Hand level. 15-21

Figure 15-38.-Using a Jacob's staff with a hand level.

Figure 15-39.-Dumpy level.

length. This stick is known as Jacob's staff, as shown in figure 15-38. For rough work, you may ignore the use of a stick and merely use the height of your eye above the ground in your normal standing position.

The hand level is used for checking grade during the rough or early part of a construction project and is not used at distances greater than about 50 feet or even lesser distances if an accuracy of more than 2 or 3 tenths is required.