other existing utilities, there should be existingutilities maps that can be used in the design of the newutility line. Consequently, in cases such as this,reconnaissance and preliminary surveys are seldomnecessary. On the other hand, a power transmissionline or other utility running through open country ona large military installation may require reconnais-sance and preliminary surveys in addition to the final-location survey.For discussion purposes, let’s consider routesurveys for overhead electrical lines.Route Surveys for Overhead ElectricalDistribution and Transmission LinesThe reconnaissance survey for electrical powerlines employs many of the same principles andpractices that you studied for highway work; however,the design considerations are different. For a powerline, the design engineer considers principles that youstudied in chapter 2 of this TRAMAN to select one ormore tentative routes over which the line will pass. Forconvenience, those principles are listed as follows:1. Select the shortest possible route.2. Follow the highways and roads as much aspossible.3. Follow the farmer’s property or section lines.4. Route in the direction of possible future loads.5. Avoid going over hills, ridges, swamps, andbottom lands.6. Avoid disrupting the environment.During the reconnaissance phase, you should firststudy all available maps of the area to gain a generalunderstanding of the landscape. If a portion of the lineis off the military installation, determine the owner-ship of the lands through which the line will pass. Thatis necessary to obtain permission to run the line. Lookfor any existing utilities that may already exist inthe area. If there are existing utilities, then look forexisting utilities maps. Visit the area to examine theterrain and look for any natural or man-made featuresthat may hinder or help the construction. In short,gather all information that the engineer will need toselect one or more general routes for the power line.With the tentative route or routes selected, you areready to conduct a preliminary survey from which amap is prepared showing the country over which theline will pass. Since the final location is not known, awide strip of land needs to be mapped. When runningthe preliminary survey, incorporate all pertinenttopographic information into the field notes. Noteparticularly any existing overhead or undergroundlines and indicate whether they are power orcommunications lines. Locate such features as hills,ridges, marshes, streams, forests, roads, railways,power plants, buildings, and adjacent military campsor bases.When the preliminary mapping is completed, theengineer selects the final route. Again, the engineerconsiders the principles listed above to select theroute.POLE LINE SURVEYS.— When the route hasbeen selected, a plan and profile are plotted. The planshows the route the line will follow and the significanttopography adjacent to the route. The profile showsthe ground elevation along the line and the top eleva-tions of the poles. These elevations are set in accord-ance with minimum allowable clearances specified inthe National Electrical Safety Code (NESC), ANSIC2, and the most recent edition of the NationalElectrical Code® (NEC®).For distribution lines, poles should be placed onthe side of the street that is most free of other lines andtrees. Try to keep off the main streets. As much aspossible, you should use the same side of the roadthroughout the length of the line. For straight portionsof lines, the usual spacing between poles is about 125feet (100 feet minimum and 150 feet maximum);however, to make the poles come in line with propertylines or fences, the span length may need to beadjusted. The engineer will determine the spans.Along roads, poles should be placed 2 feet from theinside edge of the curb or 2 feet from the edge of theroad surface where curbs do not exist. On openroadways or highways, poles should be set 18 inchesfrom the outside of fences.For transmission lines, poles should be located inhigh places so that shorter poles can be used and stillmaintain the proper ground clearance at the middle ofthe span. Avoid locating poles along the edge ofembankments or streams where washouts can beexpected. In rolling country, the grading of the lineshould be considered when determining polelocations. A well-graded line does not have any abruptchanges up or down the line and will appear nearlyhorizontal regardless of small changes in ground level.Sometimes, by shifting a pole location a few feet, astandard length pole can be used where otherwise anodd-sized pole would be needed. In addition,transmission line poles should be located at least 2 feet10-2
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