source also lends itself readily to the purification equipment common to most engineer units. Surface water is the most easily developed source of water. Methods of constructing intake points for land surface water sources are discussed below.

If the stream is not too swift and the water is sufficiently deep, an intake may be prepared quickly by placing the intake strainer on a rock. This will prevent clogging of the strainer by the streambed and provide enough water overhead to prevent the suction of air into the intake pipe. If the water source is a small stream or shallow lake,

Figure 9-5. - Direct intake with hose on bottom of water source.

the intake pipe can be secured to a post or pile as shown in figure 9-5.

When a stream is so shallow that the intake screen is not covered by at least 4 inches of water, a pit should be dug and the screen laid on a rock or board placed at the bottom of the pit. Pits dug in streams with clay or silt bottoms should be lined with gravel to prevent dirt from entering the purification equipment (fig. 9-6). The screen is surrounded by gravel to prevent collapse of the sides of the pit and also shield the screen from damage by large floating objects. The gravel also acts as a coarse strainer for the water. A similar method may be provided by enclosing the intake screen in a bucket as shown in figure 9-7.

The level of the water in small streams can be raised to cover the intake strainer by building a dam.

In swiftly flowing streams, a wing or baffle dam can be built to protect the intake screen without impounding the water.

Floats made of logs, lumber, sealed cans, or empty fuel drums can be used to support the intake strainer in deep water. Floats are especially useful in large streams where the quality of the water varies across its width or where the water is not deep enough near the banks to cover the intake strainer. The intake point can be covered by an adequate depth of water by anchoring or stationing the float at the deep part of the stream. The intake hose should be secured to the top of the float, allowing enough slack for movement

Figure 9-6. - Surface intake with hose buried in gravel-filled pit.