Ala wai openhouse_presentation_20may2014_draft
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  • 1. Ala Wai Canal Projectj Flood Risk Management Project Open House Meetings Athline Clark Project Manager Civil and Public Works Branch U.S. Army Corps of Engineers Honolulu DistrictHonolulu District May 20 and 21, 2014 US Army Corps of Engineers BUILDING STRONG®
  • 2. Ala Wai Canal ProjectProject Authority: Section 209 of the Rivers & Harbors Act of 1962 Non-Federal Sponsor: State of Hawaii (DLNRState of Hawaii (DLNR Engineering Division) Key Partner: Cit d C t fCity and County of Honolulu (ENV) Product: Integrated Feasibility Report and Environmental Impact Statement BUILDING STRONG® (EIS) 2
  • 3. Historical Perspective Ala Wai Canal was built toAla Wai Canal was built to provide drainage, not for flood protection (estimated capacity for 10-percent chance flood) Non-systematic flood projects result in reduced capacityresult in reduced capacity Aging and inadequate drainage infrastructuredrainage infrastructure Multiple flood events have overtopped Canal in past BUILDING STRONG® 3 pp p century, resulting in property damage and loss of life
  • 4. PROJECT DEVELOPMENT PROCESSPROJECT DEVELOPMENT PROCESS Sponsor R t NEPA 100% federally funded Request NEPA Purpose dependent Purpose dependent 100% non-federally funded BUILDING STRONG® 4
  • 5. 19981998 Ala Wai Canal Flood Control Project initiated Reconnaissance study for Project History 20002000 20022002 Reconnaissance study for ecosystem restoration; added to Ala Wai Flood Control Project Cost Share agreement signed with DLNR, renamed Ala Wai20022002 20042004 with DLNR, renamed Ala Wai Watershed Project ManoaManoa FloodFlood Ala Wai Watershed Project 20062006 Ala Wai Watershed Project expanded to include upper watershed NRCS funded to identify 20082008 20102010 NRCS Manoa Technical Study incorporated into Ala Wai NRCS funded to identify actions to reduce flooding in Manoa 20102010 20122012 Watershed Project Analysis of baseline conditions completed Rescoping of remainder of feasibility study BUILDING STRONG® feasibility study 20142014 Anticipated issuance of Final Feasibility Study and EIS Anticipated issuance of Draft Feasibility Study and EIS
  • 6. Project Objective Reduce riverine flood hazards to property and life safety in the Ala Wai watershed, including: Improving waterImproving water conveyance; Using environmentally t i bl d i f fl dsustainable design for flood risk management features, where practicable; and Integrating non-structural approaches, where practicable BUILDING STRONG® p 6
  • 7. 100-Year FloodplainFloodplain (Existing Conditions) BUILDING STRONG®
  • 8. BUILDING STRONG® 8
  • 9. Estimated Damages •3,000+ properties in modeled floodplain for the 1% annual chance flood (100-year event) •Estimated property damages ~$397 million (2013 price level) •Life safety risk (~54 000•Life safety risk ( 54,000 residents, ~85,000 students/ workers, ~79,000 Waikiki visitors in existing floodplainvisitors in existing floodplain •Flooding of surface streets, impacting emergency access •Impacts to critical infrastructure (e.g., power, telecommunications, sewer, BUILDING STRONG® 9 water)
  • 10. Alternatives Formulation Process BUILDING STRONG® 10 Variations based on further analysis and refinement
  • 11. Criteria Used in Alternative iFormulation Process T h i l f ibilit Fl d i k d tiTechnical feasibility Implementation cost O& Flood risk reduction Life safety risk reductionO&M requirements Cost-effectiveness reduction Community resilience E i t l i tAvailability of land Acceptability Environmental impact Archaeological/cultural impactSocial fairness impact BUILDING STRONG® 11
  • 12. Approaches/Tradeoffs Considered in Alternati es Formulation ProcessAlternatives Formulation Process Approaches: Tradeoffs:Approaches: Attenuate water where the highest volume of peak flows occur upper Manoa Tradeoffs: Potential issues with public acceptability of one measure over anotherflows occur – upper Manoa and Palolo Attenuate water within tl d l d measure over another Use of the golf course and/or park space for d t ti i t tcurrently developed portions of the watershed Maximize solutions where h j i f h fl d detention versus impacts to forest reserve lands Holding large volumes of i Mthe majority of the flood risk occurs – the lower watershed, including Waikiki water in upper Manoa versus building higher levees in Waikiki BUILDING STRONG® 12
  • 13. Alt. 3A. 3 (Conceptual) F th l i d• Further analysis and refinement may result in variations f lt tiof alternative • Tentatively Selected Plan to be identifiedPlan to be identified from these variations BUILDING STRONG®
  • 14. Detention Basins (Mid to Upper Watershed) Earthen berm across channel 20-24 feet high Arch culvert (allows small storm flows to pass) Vegetation to be kept clear within 20’ perimeter around berm Emergency spillway (riprap) N t id d l t d dNot considered regulated dam Mitigation to be incorporated Inundation area Generally < 1 acre, drains in ~9-12 hours (1% chance storm) O&M requirements BUILDING STRONG® 14 q Sediment/debris removal Vegetation clearing
  • 15. Waihi Stream Detention Basin (Manoa) BUILDING STRONG® 15
  • 16. Conceptual Renderings of DetentionDetention Basins Waiakeakua Stream (Manoa) Pukele Stream (Palolo) BUILDING STRONG®
  • 17. Conceptual Renderings of DetentionDetention Basins Woodlawn Ditch (Manoa) Makiki Stream BUILDING STRONG®
  • 18. Debris Catchment Debris catchment structure 8' wide concrete pad Steel posts (Up to 7' high),p ( p g ), spaced every 4' along concrete pad Excavation to allow high fl it ( tflows across site (at Innovation Center) Mitigation to be incorporated O&M i tO&M requirements Debris removal BUILDING STRONG®
  • 19. Manoa In-Stream Debris Catchment BUILDING STRONG® 19
  • 20. Ala Wai Canal Floodwalls Wall / berm set back from existing walls Up to 5’ feet highUp to 5 feet high Flap/slide gates and pump stations to prevent back flow via existing drainage featuresg g Bridges and roadways to be maintained (possibly some impacts along Ala Wai Blvd) Recreational access to be maintained (design features to be determined) Aesthetic improvements may beAesthetic improvements may be added by non-federal sponsor Impacts to historic floodwalls to be considered, with mitigation BUILDING STRONG® 20 be considered, with mitigation as appropriate
  • 21. Ala Wai Canal Floodwalls BUILDING STRONG® 21
  • 22. Conceptual Renderings ofRenderings of Ala Wai Canal Floodwalls BUILDING STRONG® 22
  • 23. Detention Basins (Lower Watershed) Earthen berm around detention area Up to 5 feet highUp to 5 feet high Passive drainage back into Ala Wai Canal Slide/sluice gates at HaustenSlide/sluice gates at Hausten Bridge Multi-purpose features Detention area currentlyDetention area currently floods in 1% chance storm Recreational activities to be maintained during non-floodg periods O&M requirements Sediment and debris removal BUILDING STRONG® 23Slide/sluice gate maintenance (Hausten Ditch)
  • 24. Ala Golf Course Detention Basin BUILDING STRONG® 24
  • 25. Hausten Ditch Detention Basin BUILDING STRONG® 25
  • 26. ConceptualConceptual Renderings of i iDetention Basins Ala Wai Golf Course Hausten Ditch BUILDING STRONG® 26
  • 27. Key Challenges and Opportunitiesy g pp Challenges: Funding for future phases Opportunities: Stakeholder support forg p of the project (both federal and local) No solution will eliminate pp continued funding Flood risk planning is a necessity now and in theNo solution will eliminate all risk of flooding Non-federal sponsors are necessity, now and in the future Special area designationp responsible for operations/maintenance S p g may help resolve O&M constraints P t ith kSome measures may benefit from aesthetic improvements Partner with key organizations to aesthetically improve BUILDING STRONG® flood measures 27
  • 28. Schedule to Complete Study MILESTONE ANTICIPATED COMPLETION DATE Public Review of Draft Feasibility ReportPublic Review of Draft Feasibility Report and Environmental Impact Statement (EIS) Fall 2014 Development of detailed design and cost for Wi t 2014 S i 2015 Development of detailed design and cost for Final Feasibility Study/EIS Winter 2014 – Spring 2015 R l Fi l F ibilit R t/EIS F ll 2015Release Final Feasibility Report/EIS Fall 2015 Chief’s Report (USACE Recommendation Fall 2015 ( to Congress) Fall 2015 BUILDING STRONG® 28
  • 29. Questions?Q For more information contact:For more information contact: Athline M. Clark Project Manager, USACEj g , 808-835-4032 athline.m.clark@usace.army.mil BUILDING STRONG® 29