direction of the line gradient and often shaped withchannels for carrying the water across the box fromthe inflowing pipe to the outflowing pipe.STORM SEWER ROUTE SURVEY.— Thecharacter of the route survey for a storm sewerdepends on the circumstances. The nature of theground may be such as to indicate, without thenecessity for reconnaissance and preliminary locationsurveys, just where the line must go. This is likely tobe the case in a development area; that is, an area thatwill be closely built up and in which the lines of thestreets and locations of the buildings have alreadybeen determined. In these circumstances, thereconnaissance and preliminary surveys may be saidto be done on paper.On the other hand, a line—or parts of it—oftenmust be run for considerable distances over rough,irregular country. In these circumstances the routesurvey consists of reconnaissance, preliminarylocation, and final-location surveys. If topographicmaps of the area exist, they are studied to determinethe general area along which the line will be run. If nosuch maps exist, a reconnaissance party must selectone or more feasible route areas, run random traversesthrough these, and collect enough topo data to makethe planning of a tentative route possible.After these data have been studied, a tentativeroute for the line is selected. A preliminary surveyparty runs this line, making any necessary adjustmentsrequired by circumstances encountered in the field,taking profile elevations, and gathering enough topodata in the vicinity of the line to make design of thesystem possible.The system is then designed, and a plan and profileare made. Figure 10-3 shows a storm sewer plan andprofile. The project here is the installation of 230 feetof 18-inch concrete sewer pipe (CSP) with a curb inlet(CI “A”). The computational length of sewer pipe isalways given in terms of horizontal feet covered. Theactual length of a section is, of course, greater than thecomputational length because of the slope.The pipe in figure 10-3 is to run downslope froma curb inlet to a manhole in an existing sewer line. Thereason for the distorted appearance of the curb inletand manhole, which look much narrower than theywould in their true proportions, is the exaggeratedvertical scale of the profile. The appearance of the pipeis similarly distorted.The pipe to be installed is to be placed at a gradientof 2.39 percent. The invert elevation of the outflowing21-inch pipe at the manhole is 91.47 feet; that of theinflowing 18-inch pipe is to be 92.33 feet. Obviously,there is a drop here of 0.86 foot. Of this drop, 0.25 footis because of the difference in diameters; the other0.61 foot is probably because of structural andvelocity head losses.From the invert in at the manhole, the new pipewill extend 230 horizontal feet to the invert at thecenter line of the curb inlet. The difference inelevation between the invert elevation at the manholeand the invert elevation at the curb inlet will be theproduct of 2.39 (the grade percentage) times 2.30(number of 100-foot stations in 230 horizontal feet),or 5.50 feet. Therefore, the invert elevation at the curbinlet will be 92.33 feet (invert elevation at themanhole) plus 5.50 feet, or 97.83 feet. The invertelevation at any intermediate point along the line canbe obtained by similar computation.The plan shown in figure 10-3 is greatly simplifiedfor the sake of clearness—it contains the bareminimum of data required for locating the new line.Plans used in actual practice usually contain moreinformation.The plan and profile constitute the paper locationof the line. A final-location survey party runs the linein the field. Where variations are required because ofcircumstances discovered in the field (such as thediscovery of a large tree or some similar obstructionlying right on the line), the direction of the line isaltered (after receiving approval to do so) and the newline is tied to the paper location. The final-locationparty may simply mark the location of the line and takeprofile elevations, or it may combine the final-locationsurvey and the stakeout (which is part of theconstruction survey, rather than the route survey) inthe same operation.Other Route SurveysWhile highways and the various types of utilitieshave differing design requirements that must beconsidered when conducting route surveys, you haveprobably observed in your studies that much of routesurveying is similar regardless of the type ofconstruction being planned. This is especially trueduring the reconnaissance phase. Therefore, with afirm understanding of the preceding paragraphs andof the EA3 TRAMAN discussion of route surveying,you should have little difficulty in planning andperforming other types of route surveys. For roadsand highways, however, you also must have an10-6
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business