All earth dams must be provided with a wasteway, ample to discharge the maximum flood tributary to the reservoir. Whatever type of wasteway be adopted, no reliance should ever be put upon the outlet pipes for this purpose. The outlet should only figure as a factor of safety for the wasteway, insuring, as it were, the accuracy of the estimated flood discharge. The safety of the dam demands that ample provision be made for a volume of water in excess of normal flood discharge. This most necessary adjunct of earth dams may be an open channel, cut through the rim of the reservoir basin, discharging into a side ravine which enters the main drainage way some distance below the dam. It may be necessary and possible to pierce the rim by means of a tunnel where its length would not prohibit such a design. Lastly, there may be no other alternative than the construction of an overfall spillway, at one or both ends of the embankment. This last method is the least desirable of any and should be resorted to only when the others are impracticable; even then, the volume of water, local topography, geology, and constructive materials at hand must be favorable to such a design. If they are not favorable it may be asked, “what then?” Simply do not attempt to build an earth dam at this site. PHYSICAL FEATURES, MATERIALS, ETC.–An investigation of the location and the physical features of the dam site should include a careful and scientific examination of the materials in the vicinity, to determine their suitability for use in construction. An earth embankment cannot be built without earth, and an earth dam cannot be built with safety without the right kind of earth material. Test pits judiciously distributed and situated at different elevations will indicate whether there is a sufficient amount of suitable material within a reasonable distance of the dam. The type of earth dam best suited for any particular locality, and its estimated cost, are thus seen to depend upon the data and information obtained by these preliminary studies. Economical construction requires the use of improved machinery and modern methods of handling materials, but far more important even than these are the details of construction.