Phase A - Alternatives Analysis Report - Urban Drainage and Flood ...

PHASE A – ALTERNATIVES ANALYSIS REPORTMajor Drainageway Planning Update for Hidden Lake-Bates Lake6 ALTERNATIVE EVALUATION6.1 Evaluation ProcessAlternatives were evaluated on a reach by reach basis. Several factors were considered in the evaluationprocess. These factors include: effectiveness in reducing the 100-year floodplain limits, project costs, publicsafety, impact on wetland and other natural resources and habitat, implementation of other priorities for thecorridor including RTD/FasTracks.6.2 Combination of AlternativesFor some of the reaches it made sense to combine some of the alternatives mentioned in Section 5 togetherto provide the best overall plan to provide a means of improving stormwater conveyance, reducing flooding,and improving stormwater quality for the reaches identified in the Hidden Lake and Bates Lake project area.Reach H-1 and Reach B-1 where the two reaches that were benefited by a combination of alternatives.6.2.1 Reach H-1This reach extends from the Hidden Lake watershed headwaters, near the intersection of Carr Street and 69 thPlace to the intersection of Sheridan Boulevard and 69 th Avenue. A schematic of this reach can be seen onFigure 5-1.Alternative 5a: Combination of AlternativesThis alternative is a combination of Alternatives 2a, 4a, 3b, and 3c. This alternative takes into considerationthe peak flood attenuation that is occurring in Alternative 2a when sizing Alternatives 3b and 3c. Thisalternative eliminates the flooding along Reach H-1 as well as the overtopping of Sheridan Boulevard in a100-year storm event.Alternative 5b: Combination of AlternativesThis alternative is a combination of Alternatives 2b, 3b, and 3c. This alternative takes into consideration thepeak flood attenuation that is occurring in Alternative 2b when sizing Alternatives 3b and 3c. Thisalternative eliminates overtopping of Sheridan Boulevard in a 100-year storm event.Alternative 5c: Combination of AlternativesThis alternative is a combination of Alternatives 3a, 3b, and 3c. This alternative eliminates the floodingalong Reach H-1 as well as the overtopping of Sheridan Boulevard in a 100-year storm event.Alternative 5d: Combination of AlternativesThis alternative is a combination of Alternatives 3b and 3c. This alternative eliminates overtopping ofSheridan Boulevard in a 100-year storm event.Alternative PlanTable 6-1: Reach H-1 Combination of Alternatives Cost EstimatesStructuralImprovementsTrafficControlUtilityRelocationsREACH H-1: Watershed Headwaters to Sheridan Boulevard5a5b5c5dCombination ofAlternatives 2a, 4a,3b & 3c.Combination ofAlternatives 2b, 3b& 3c.Combination ofalternatives 3a, 3b,& 3c.Combination ofalternatives 3b &3c.PropertyAcquisitionEngineering,CM, &ContingenciesOperation &MaintenanceAlternativeTotal$965,596 $89,975 $59,983 $15,585 $337,959 $47,000 $1,516,098$746,915 $94,420 $62,946 $15,585 $261,420 $24,000 $1,205,286$4,705,677 $303,307 $470,568 $15,585 $1,646,987 $57,000 $7,199,124$680,232 $102,035 $68,023 $15,585 $238,081 $17,000 $1,120,9566.2.2 Reach B-1This reach extends from the Bates Lake watershed headwaters, near the intersection of Pierce Street and 67 thAvenue, to the intersection of Sheridan Boulevard and the Union Pacific Railroad. A schematic of thisreach can be seen on Figure 5-5.Alternative 5a: Combination of AlternativesThis alternative is a combination of Alternatives 2b, 4c, 3a and 3b. This alternative takes into considerationthe peak flood attenuation that is occurring in Alternative 2b when sizing Alternatives 3a and 3b. Thiscombination of four alternatives conveys the entire 100-year peak runoff tributary to the intersection ofSheridan Boulevard and the Union Pacific Railroad, eliminates the overtopping of the Union PacificRailroad, eliminates the flood of structures north of the tracks between Sheridan Blvd. and Tennyson St.,and eliminates the overtopping of Tennyson St.Alternative 5b: Combination of AlternativesThis alternative is a combination of Alternatives 3a and 3b from Reach B-1 and Alternatives 3a and 3b fromReach B-2. This combination of four alternatives conveys the entire 100-year peak runoff tributary to theintersection of Sheridan Boulevard and the Union Pacific Railroad, eliminates the overtopping of the UnionPacific Railroad, eliminates the flood of structures north of the tracks between Sheridan Blvd. and TennysonSt., and eliminates the overtopping of Tennyson St.6-1