be used to intercept or control surface water. Theseshould be dug by bulldozers, scrapers, backhoes, ormotor graders, depending on circumstances. Culvertsare constructed to drain water across a constructionsite. Subdrains to drain groundwater are usuallyexcavated with ditchers or backhoes. The drains usedare french drains (perforated or open-joint tilepipes). Figure 15-65 shows typical covered andfrench drains.Runoff water from rain or melted snow is removedfrom the area by constructing an adequate transverseslope or crown. This runoff is collected in ditches anddrained into the nearest natural drainage channel.Drainage for construction sites can be provided bybuilding the ends of the site sloping towards themiddle or sloping from one end to the other. Thesetypes of drainage construction are shown on therunways in figure 15-66.Figure 15-65.—Typical sections of covered and french drains.Figure 15-66.—Longitudinal drainage of runways.,-15-41
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