Guidelines Bulletin 17B (Interagency Advisory Committee on Water Data, 1982) and were carried out <br />using the H-SSP v.2.1 2016). The <br />results of the peak flow evaluation where compared with the peak flows reported for the project area in <br />the Flood Insurance Study (FIS) for Lane County, Oregon (FEMA 1999a). For design purposes a <br />combination of the Bulletin 17B peak flow statistics and the FIS report values were selected as shown in <br />Figure 3. <br />Return Period (years) <br />11.525102550100200500 <br />150,000 <br />100,000 <br />70,000 <br />50,000 <br />Dec. '96 <br />30,000 <br />Gage peaks <br />Dec. '16 <br />Low outliers <br />20,000 <br />Nov. '17 <br />5% conf. limit <br />Bulletin 17B curve <br />95% conf. limit <br />10,000 <br />FEMA FIS Values <br />Project Design Values <br />5,000 <br />100%67%50%20%10%4%2%1%0.5%0.2% <br />Annual Exceedance Probability <br /> <br />Figure 3. Flood frequency analysis plot - FEMA FIS & Bulletin 17B. Gage peaks are discharge from USACE Gage EUGO at the <br />Former EWEB Steam Plant in Eugene, OR for the available post dam period of record (1976-2018). The 5% confidence, Bulletin <br />17B curve, and 95% confidence lines are from HEC-SSP version 2.1. FEMA FIS values are as reported in the Lane County Flood <br />Insurance Study (FEMA 1999a) at the former USGS Gage 14158000 at State Hwy 125 near Springfield, OR. The design values are <br />a combination of Lane County FIS (FEMA 1999a) values and Bulletin 17B analysis results. <br />The available post-dam annual peak flow record period (1976-2018) from the on-site gage (USACE <br />EUGO) was also used for the purpose of evaluating seasonal flow hydrology. A number of statistical <br />analysis were done on the data including; daily and monthly average, minimum, maximum, and flow <br />exceedance probabilities (from 5 to 95 percent). Mean daily discharges were used in the analysis and a <br />normal distribution was assumed for exceedance probability calculations. The results of these analysis <br />are shown in Figure 3. <br />12 <br />