Locating Utility Lines

It is absolutely essential to accurately locate utility lines for safety during construction, future maintenance of the utilities, and layout of the proposed design. Some utility lines are above ground and are fairly easily to locate. Other utility lines are under­ground and potentially more problematic even though they cannot be seen.

Above-Ground Utilities There are five suggested measurements for locating above­ground utilities like electricity, telephone, and cable. First, locate utility poles on or near the site by determining their position in relation to the property corners or by triangulation from two nearby corners of the house.

Second, estimate the height of the wires on the utility pole. This can be done by having an assistant stand at the base of the pole and then estimating the pole’s height in relation to this person (Figure 6-31).

Third, establish the point where the wires attach to the house by using the base­line method of measuring (Figure 6-32).

Fourth, estimate the height of the wires where they attach to the house by using the same method for approximating the height of the wires on the utility pole (Fig­ure 6-31). Another method is to measure an individual feature or element on the house wall, such as a brick or a piece of siding. Then count the number of bricks or pieces of siding there are between the ground and the point where the wires attach to the house.

Finally, it is necessary to locate the low point in the height of the wires above the ground between the utility pole and the house. The plan location of the low point can be determined by measuring along the wire or by triangulation. The height of the low point is found with the same method previously described for estimating heights (Figure 6-33). These dimensions are vital when studying the location of proposed trees and structures.

Underground Utilities Underground utilities almost always include gas, water, and sewer. In addition, underground utilities may comprise electric, telephone, and/or cable, especially in neighborhoods developed in the past 25 years. Because they cannot be seen, underground utilities are difficult to locate and are a safety hazard if they are cut or punctured. The first thing that should be done to locate underground utilities is to ask the homeowner to contact the local underground utility locating service that is usu­ally listed in the telephone directory under a “call before you dig” number. This service typically uses ground-penetrating radar (GPR) to locate utilities and then marks them on the ground surface with small colored flags and/or painted lines. This survey should be done before on-site measuring so that measurements can be taken of the markings.

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The preceding method for locating underground utilities is the most reliable and should be followed whenever possible. However, when this process is not feasible or when it is necessary to augment the information it provides, then the following steps should be taken.

First, locate the source of underground utilities along the property line, in the right-of-way, or in adjoining yards. In the case of electric or telephone lines, there may be transformers, junction boxes, or other metal containers where these utilities origi­nate. For gas and water lines, there should be shut-off valves located at or just below the ground’s surface somewhere on the site or in the street right-of-way. They usually have a cast-iron cover that identifies their location. These features can be located with the triangulation method of measuring.

Second, note the length, width, and height of the electric and telephone trans­formers and junction boxes.

Third, locate where the utilities enter the house. With a house that has a base­ment, a close inspection of the basement wall usually reveals where this occurs. If a house doesn’t have a basement, then carefully look in the crawl space or along the base of the first-floor wall to find where the utilities enter the house.

Finally, determine the depth at which the utility lines are located beneath the ground surface. This information may be difficult to find out, although contacting the various utility companies is a recommended place to start. The depths of the gas line, telephone wire, and cable are especially critical because they can easily be severed when digging into the ground.