Stephens Creek Culvert Replacement. CAC April 28, 2010

Transcription

1 Stephens Creek Culvert Replacement CAC April 28,

2 Top of Bank Willamette Moorage Park Existing Culverts 50 ft Greenway Setback 200 ft Greenway Setback Existing Macadam Bay Access Stephens Creek Existing Conditions 2

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4 Willamette Moorage Park Macadam Bay Veg. Sloped Walls Veg. Sloped Walls W. Greenway Trail To Remain Open for Emergency Access Stephens Creek Proposed Construction 4

5 Willamette Moorage Park Macadam Bay Foot Bridge W. Greenway Trail Bridge Bridge A (100 Span) Bridge A (100 Span) Elevation 5

6 Macadam Bay Willamette Moorage Park Foot Bridge W. Greenway Trail Bridge Bridge B (50 Span) Plan Bridge B (50 Span) Elevation 6

7 Willamette Moorage Park Macadam Bay Foot Bridge W. Greenway Trail Box Culvert Concrete Box Culvert Plan Concrete Box Culvert Elevation 7

8 Willamette Moorage Park Macadam Bay Foot Bridge W. Greenway Trail Open Arch Culvert Open Bottom Metal Plate Arch/Precast Concrete Arch Culvert Plan Open Bottom Metal Plate Arch/Precast Concrete Arch Culvert Elevation 8

9 Macadam Bay Willamette Moorage Park Foot Bridge W. Greenway Trail Ellipse Metal Plate Ellipse Plan Metal Plate Ellipse Elevation 9

10 Culvert Profile Construction Duration/ Trolley Closure Duration In-water Construction Aquatic Benefits Terrestrial Habitat Benefits Opportunties for Re- Vegetation Long Term Maintenance Bridge A (100' span) 6 mo + Bridge can be constructed outside Open bottom of in-water work provides window, limiting natural aquatic amount of work disturbances to the stream Provides unrestricted terrestrial Large area under the bridge will remain without water or light limiting re-vegetation Another bridge to maintain Bridge B (50' span) 6 mo + Bridge can be constructed outside Open bottom of in-water work provides window, limiting natural aquatic amount of work disturbances to the stream Provides terrestrial Smaller area under the bridge (low flow channel and the floodplain bench) - more area for vegetated slopes (See for details) Another bridge to maintain Concrete Box Culvert 6 mo - Most work would Closed bottom need to be culvert provides completed within simulated the in-water work streambed window Provides terrestrial Large area for revegetation on steepened side slopes Potential for blowout of simulated streambed in high flow situations Evaluation matrix 10

11 Sellwood Bridge Stephens Creek Alternative Evaluation Matrix Construction Duration/ Trolley Closure Duration In-water Construction Aquatic Benefits Terrestrial Habitat Benefits Opportunties for Re- Vegetation Long Term Maintenance Construction Cost (2014 $) Bridge A (100' span) 6 mo + Bridge can be constructed outside of in-water work window, limiting amount of work disturbances to the stream Open bottom provides natural aquatic Provides unrestricted terrestrial Large area under the bridge will remain without water or light limiting re-vegetation Another bridge to maintain 4.6M Bridge B (50' span) 6 mo + Bridge can be constructed outside of in-water work window, limiting amount of work disturbances to the stream Open bottom provides natural aquatic Provides terrestrial Smaller area under the bridge (low flow channel and the floodplain bench) - more area for vegetated slopes Another bridge to maintain 2.5M Concrete Box Culvert 6 mo - Most work would need to be completed within the in-water work window Closed bottom culvert provides simulated streambed Provides terrestrial Large area for re-vegetation on steepened side slopes Potential for blowout of simulated streambed in high flow situations 2.9M Open Bottom - metal plate arch/ precast concrete arch culvert 3 mo + Most work would need to be completed within the in-water work window Open bottom provides natural aquatic Provides terrestrial Large area for re-vegetation on steepened side slopes Long term corrosion issues with metal plate Precast concrete has lower maintenance 2.3M Metal plate ellipse 4 mo - Most work would need to be completed within the in-water work window Closed bottom culvert provides simulated streambed Provides terrestrial Large area for re-vegetation on steepened side slopes Long term corrosion issues with metal plate Potential for blowout of simulated streambed in high flow situations 2.3M Precast Concrete Box Culvert (low clearance) 3 mo + Most work would need to be completed within the in-water work window Closed bottom culvert provides simulated streambed Provides terrestrial Large area for re-vegetation on steepened side slopes Potential for blowout of simulated streambed in high flow situations 1.5M All alternatives meet SLOPES IV criteria for functional floodplain.

12 Sellwood Bridge Willamette River Non-numbered Stream Existing Culvert Stream #1 New Culvert Powers Marine Park Stephens Creek Possible Wildlife Crossing 11