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When duplicating assumptions and report. the earlier results of the Corps, their methodology were used where stated in their Specifically, the Bulletin states that if regional skew information is available, it should be used by the analyst, In the case of the gage at the bluffline, Table 1 of the 1981 report (Appendix 4) indicated that a regional skew of +1.0 be used for the mountainous terrain involved. In the case of the Greeley gage, no such information was available, and the generalized skew map contained in Bulletin #17B was consulted. The map (Appendix 6) indicated that a value of - 0.1 be used for the area, At the B1uff1ine As mentioned previously, the Corps in their 1973 study computed a peak lOa-year discharge of 17,400 cfs. An analysis of their data set by our firm produced station statistics very close to those computed in the 1973 study (Appendix 1). As it is unlikely' that the methods used to compute these have changed, and all computations were performed using logarithms, it is assumed that roundoff errors are the cause of any discrepancy in the mean or standard deviation computed. The 1973 study did not weight the station skew, but instead adopted a regional skew of +1.0 to shape the final curve, By using the Corps data set and adopting the Corps regional skew, the 100-.year peak discharge was calculated by our firm as 17,427 cfs, The station statistics (number of data points, mean, and standard deviation) calculated by the Corps in 1981 are not published in their report, Conversations with personnel from the Omaha branch, who published the study revealed that this information was not readily available, and that the methods used to adjust the data for the historical extension have changed since that time. Further, the final curve published in the 1981 report was adju.sted upward for expected probability. The lOa-year discharge from the 1981 Corps' curve (Figure 2, Appendix 4) is 16,500 cfs. Subtracting the adjustment for expected probability of 700 cfs (from the conversation with the Corps), gives a value for the lOa-year discharge published by the COl:'PS of 15,800 cfs. Our firm analyzed the data set from 1910 to 1976, and included the 1904 flood of 25,000 cfs as a historic event using the guidelines of Bulletin #17B. The historically adjusted station statistics were calculated and, weighting the calculated skew of 0.992 with a regional skew of +1.0 gave a weighted skew of 0.995. This was used by our firm to calculate the laO-year discharge as 15,008 cfs for the 1981 Corps data set. Page 8