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SECTION 3 Flood Control Euaination 3.5.1 Capital Projects to Address Capacity Deficiencies All flooding problems (i.e., capacity deficiencies) identified through modeling and proposed capital projects (CPs) to address these problems are referenced in Table 3 -2 and presented in Table 3 -5. Prior to this study, design standards for flood protection levels in Eugene were based on the previous storm drainage master plan (OTAK 1990). The 1990 plan includes varying degrees of protection depending on the size of the drainage area, type of system (open channel or pipe), and type of roadway (local collector vs. major arterial). Depending upon these factors, the standards for designing CIPs ranged from the 5 -year to the 50 -year recurrence interval storm. For this plan, the City elected to retain the flood protection levels listed in the 1990 plan with the exception that the minimum level of protection would be the 10 -year as opposed to the 5 -year storm (see Section 3.1.4, Table 3 -1 of Volume 1 for exceptions). Flooding problems were identified for the open waterways and the pipe system and CIPs were developed based on the relevant design storm as listed in Table 3 -2. A flooding problem was identified for an open waterway if the water depth exceeded the top of bank elevation. For the pipe system, surcharging was allowed, however, if the water entered the street a flooding problem was identified. In all, 10 flood control CPs focused on existing culvert replacement and upsizing of the culverts are proposed. Two CPs are proposed that include regrading of the existing channel to improve conveyance capacity. Three CPs are associated with providing storage to relieve predicted capacity issues and one CP is associated with additional survey efforts. Table 3 -5 Capacity Deficiencies Identified Through Modeling and Proposed Capital Projects to Address Them Selected Flood Controlapital' elected Flood Control Capital Conduits Addressed with Capital Project Name Project Descri tion Project Al Channel AM Regrade the existing open channel RSA1090B, RSA1090CI and C2, segment (RSA1090B) from node and RSA1090D 72789 to 78790 (18'). Al -2 Upsize and replace the existing 36" RSA1090A, RSA1090B, CMP culvert (RSA1090A) with a RSA1090CI and C2, and 48" CMP culvert. RSA1090D Al -3 Construct storage facilities at nodes RSA1090A, RSA1090B, 72782 and 72102 to provide a total RSA1090CI and C2, RSA1090D, of 85 acre -ft of storage. RSA1090E1, E2, and E3, RSA1090F, RSA1080B, RSA1060H, RSA1060M, RSA10600, RSA1060Q, RSA I060U, RSA 1100B.1, RSA1100C, RSA1100D.1, RSA1100E, RSA1100F.1, RSA 1100G, RSA I100H, and RSA 1100K Al -4 Upsize and replace the existing 24" RSA I100I.1, RSA 1100J, CMP culvert (RSA11001) with a 36" RSA1110A1 and A2 CMP culvert. 0: 25695978 Eugene RR -SC Final Basin P1an\Master P1anTINAL 2- 2010\Master_Plan 3- 11- 10_FINAL_ Word _Version.doc 3-11