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Table 7 <br />Event RDII Volume vs. Rainfall Achieved Compared to WWFMP Predictions <br />(Excerpts from Figure 5-10 in the WWFMP} <br /> Percent of Total Pipe WWFMP Estimated Achieved <br /> Rehabilitated RDII Volume (%) <br /> (%) Reduction Public Only <br /> System* <br /> (%) <br />Sub-basin 84 49 26 <br />DA-21 <br />Sub-basin 64 44 43 <br />DA-22 <br />Sub-basin 91 50 71 <br />DA-23 <br />Sub-basin 56 42 59 <br />DA-24 <br />* Public Only System Rehabilitation recommended by WWFMP <br />Based on the results of this analysis, it is reasonable to conclude that the City of Eugene's <br />rehabilitation program has been successful and should continue as it is currently being <br />implemented. <br />Two recommendations for the City to consider relative to monitoring the flow-reduction <br />progress of rehabilitation projects are more detailed modeling and detailed mapping of <br />rehabilitation projects. The R-value method of effectiveness assessment provides a reasonable <br />metric that could be enhanced or complemented with computer modeling at the sub-basin <br />level. Because RDII is influenced significantly by antecedent moisture conditions in the soil, <br />the flow versus rainfall and the RDII volume versus rainfall graphs can be quite scattered in <br />the R-value method. Therefore, comparing the slopes of the lines before and after <br />rehabilitation may not give a full representation of the RDII reduction actually achieved. <br />Calibrating the City's RDII simulation model to the sub-basin level would provide the <br />advantage of including the antecedent moisture conditions in the soil and providing simulated <br />long-term periods (in addition to monitoring periods) over which to evaluate RDII reduction <br />effectiveness. <br />More detailed mapping of the sub-basins undergoing rehabilitation would augment the <br />descriptions and analysis described in this report. Information amenable to spatial <br />presentation (GIS mapping) that would support a reader's understanding could include: <br />• Maps of basins being evaluated <br />• Highlight of wastewater collection system portions that have undergone rehabilitation <br />(possibly color coded by date of rehabilitation) <br />• Mapping indication ofnon-standard rehabilitation (e.g., outside the public right-of- <br />way) <br />• Mapping indication if objective focused primarily on inflow or infiltration reduction <br />• Location of monitoring locations <br />• Location of rainfall gauges used in the analysis <br />34 <br />