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e e e The dam height is based on the necessary reservoir capacity plus 5 feet of freeboard. Five feet of freeboard is the minimum allowed by the Regulations, but since essentially all of the reservoirs have small surface areas the wave action should not require more than 5 feet. If freeboard is increased at any site, it was to raise the water depth over the spillway to pass the inflow design flood. The maximum crest width is 25 feet as stated in the Rules and Regulations. The typical upstream slope is 3.0H:l.OV and the downstream slope is 2.5H:l.OV, which should provide a good factor of safety unless the soils tests shows the material to have some deficiency. If there is an impervious core with a pervious shell, the impervious core has minimum slopes of 1.OH:l.OV upstream and downstream. The embankment quantity is estimated by using the best available topography to determine the cross section at the dam centerline; the average end area method is used to estimate the volume. The embankment volume is increased by 30% for compaction to determine the quantity of material to be placed. If an RCC dam best fits the site, the upstream slope is vertical and the downstream slope is 0.8H:l.OV, as suggested in the publication "Roller Compacted Concrete II". A cutoff trench is included in all embankments, normally 20 feet wide and 20 feet deep. The trench wall is assumed vertical for quantity estimates but will probably not be vertical in actual construction. The crest width is determined from the Regulations which state that the crest width shall be the "height divided by 5 plus 10 feet" or 25 feet which ever is less. The outlet pipe size, if not an enlargement, is assumed to be larger than necessary, usually 3 or 4 feet in diameter. The pipe material is suggested to be reinforced concrete or steel. A slide gate is included if not already in place. Most of the dams include a hand wheel to control the gate; a motorized control mechanism is needed on only a few of the dams. The appropriate inflow design flood to be passed around the dam is based on Bureau of Reclamation criteria for reconnaissance studies. Where the spillway is existing, the current size is assumed to be adequate for an enlargement, unless there is a known safety problem. Most of the reservoirs have very small drainage areas. A concrete cutoff wall is included at each spillway, if not in rock, to maintain the channel shape and the channel crest elevation. Rip rap was assumed on the face of each dam to be 2 feet thick including the blanket. Small Dam Site Recon. Study 10