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. . 11 conditions, and others which are used in estimating the amount of runoff generated from a storm. We will use HYdrometeorological Report No. 55 for estimating' the "Probable ~Iaximum Precipi ta tion" (PMP). The 100 year storm precipitation values will be taken from NOAA Atlas No.2. Flood hydrographs will be determined using the synthetic unit hydrog~aph approach developed by the U.S. Bureau of Reclamation. We expect that both the general (areal) and thunderstorm bydrographs will have to be constructed for comparison. From our cursory review of available information we believe that it is likelY a spillwaf can be constructed that will be smaller than that required to pass the flood resulting from the PMP. This may result in considerahle cost savings in construction. To obtain the State Engineer's aPproval of such downsizing of the spillway will require an~incremental damage study. An incremen- tal damage study involves determining the expected flood plain due to an overtopping dam failure and comparing th~s flood plain to that which would occur bad the dam not been constructed. The intent is to find a spillway size and an associated inflow deSign flood such that there would be no additional loss of life or significant increase in property damage from an overtopping dam failure. Hazard Rating Analysis--This analysis is done to determine the hazard clasS of the dam. The basic steps in this analysis will be to determine the flood plain that would result from the fail- ure of the dam assuming no inflow and a full reservoir. A flood wave from the dam failure is routed in the downstream channel until the flood stage is equal to the 100 year flood plain, An analysis of the possihle damage from such a failure is tben the basis for the hazard classification.