1. AHWATUKEE-FOOTHILLS ADMS MANDAN STREET DESIGN CHARRETTE Valerie Swick, Project Manager Flood Control District of Maricopa County

2. Mandan St. Design Charrette Meeting Purpose Develop a consensus alternativeDevelop a consensus alternative Build support needed for implementationBuild support needed for implementation Identify other project opportunities or constraintsIdentify other project opportunities or constraints

3. Design Charrette Meeting Agenda Welcome/IntroductionsWelcome/Introductions Area Drainage Master Study OverviewArea Drainage Master Study Overview Mandan Street Project NeedMandan Street Project Need Preliminary Alternatives OverviewPreliminary Alternatives Overview Design Charrette Process and ConsiderationsDesign Charrette Process and Considerations Consensus Alternative DevelopmentConsensus Alternative Development Next StepsNext Steps

4. Introductions

5. Ahwatukee-Foothills ADMS

6. Project PurposeProject Purpose –Identify flood hazards –Identify problems –Develop possible solutions City of Phoenix a partnerCity of Phoenix a partner

7. Mandan Street Flooding Mandan Street Flood Risk

8. Mountain runoff into backyards has damaged residential properties Warner/Elliot Loop Mandan St.

9. Mandan Street Flood Risk Mountain runoff ponds behind residentsMountain runoff ponds behind residents Some residents have been flooded more than onceSome residents have been flooded more than once Homeowner wall extensions contributing to floodingHomeowner wall extensions contributing to flooding

10. Mandan Street Flood Risk Mountain runoff ponds behind residentsMountain runoff ponds behind residents Some residents have been flooded more than onceSome residents have been flooded more than once Homeowner wall extensions contributing to floodingHomeowner wall extensions contributing to flooding

11. Preliminary Flood Mitigation Alternatives Nine preliminary alternatives developed and presented to the public for commentNine preliminary alternatives developed and presented to the public for comment

12. Alternative 1 - No Build (Do Nothing)

13. Alternative 2 - Preserve Boundary Floodwall

14. Alternative 3 - Floodwall 20’ E of Preserve

15. Alternative 4 - Floodwall, Swale & Berm + Optional Onsite Detention Basin

16. Alternative 5 - Remove Wall Extensions & Regrade

17. Alternative 6 - Large Natural Channel on Preserve

18. Alternative 7 - Retention Basin on Preserve

19. Alternative 8 - Storm Drain on APS Easement

20. Alternative 9 - Purchase Property, Route Flow on Streets

21. Input Received on Alternatives ResidentsResidents –Held meeting 8/15, met/spoke with others –Want options that can be done quickly w/ fewest impacts to properties, views, access APS APS –Maintain easement access & 100’ buffer around lines –Nothing 1’ above or 2’ below existing grade –Storm drain option would require special pipes ($$)

22. Resulting Proposed Alternatives Floodwall only at property line and preserve boundaryFloodwall only at property line and preserve boundary Floodwall with minor grading for positive drainageFloodwall with minor grading for positive drainage Natural channelNatural channel

23. Mandan Street Consensus Alternative Goal: Develop a consensus alternativeGoal: Develop a consensus alternative How: Use proposed alternatives, considerations, and collaborative process to build from “kit of parts”How: Use proposed alternatives, considerations, and collaborative process to build from “kit of parts” Why: Solution needs to be implementable, seek added valueWhy: Solution needs to be implementable, seek added value

24. Mandan Street Consensus Alternative “Kit of parts” concept“Kit of parts” concept

25. Mandan Street Consensus Alternative “Kit of parts” concept“Kit of parts” concept Configuration requirements Aesthetics Added value O&M

26. Significant Utilities Arizona Public Service (APS)Arizona Public Service (APS) –120 foot easement, established in 1962 –230 kV transmission line and 69 kV distribution line Grading limitsGrading limits –2 feet down –1 foot up Access concernsAccess concerns Heavy equipmentHeavy equipment APS Powerline Corridor

27. Local Concerns Resident valuesResident values –Proximity and access to the preserve –Privacy –Mountain viewshed –Watchable wildlife ABMABM –Maintain wash south of residents –Sedimentation Recent Sediment Removal with Preserve in Background

28. City of Phoenix South Mountain Park / PreserveSouth Mountain Park / Preserve –Largest municipal park in the country 16,000+ acres –Purchased by Phoenix in 1924 Chapter 26 of The Phoenix CharterChapter 26 of The Phoenix Charter –Protects Mountain Preserves like South Mountain –Requires that any proposed flood control facilities: be recommended by the Parks and Recreation Board be recommended by the Parks and Recreation Board and be established by ordinance by the City Counciland be established by ordinance by the City Council Other Concerns:Other Concerns: –Who would maintain repairs –Revegetation / restoration of any disturbed preserve lands –Access points into preserve – potential for trail connection

29. Flood Mitigation Requirements Minimum dimensions required for Proposed Alternatives to provide 100-year flood protectionMinimum dimensions required for Proposed Alternatives to provide 100-year flood protection Other spatial considerations:Other spatial considerations: –Additional disturbance for construction not shown –Access for construction/O&M not shown

30. Alternative 1 – Floodwall Flood Mitigation Requirements

32. Alternative 1 – Floodwall Examples Floodwall with View Fence (Source: 12 News; Sept. 5, 2014) Gabion Wall (Source: www.weld-mesh.com)

33. Alternative 2 – Floodwall/Drainage Flood Mitigation Requirements

35. Alternative 2 – Minor Drainage Examples

36. Alternative 3 – Channel Flood Mitigation Requirements

38. Alternative 3 – Channel Natural channel examplesNatural channel examples

39. Proposed Alternatives Pros/Cons DescriptionAlt 1.Alt 2.Alt 3. Maintains access/views to Preserve Possibly with Design Strong Pro Dual use of APS O&M road possible Yes for wall, not sediment Yes, but requires access to channel from road Requires long term maintenance Yes, wall and sediment Yes, sediment Addresses sediment NoModerate yes Provides positive drainage NoYes

40. Mandan Street Design Charrette

41. Mandan St. Alternatives Next Steps FCD and COP to identify Preferred Alternative Present Preferred Alternative to residents (2/4) Prepare 15% design concept Apply for funding If no consensus/fatal flaws on alternatives, only option is for minor improvements on properties projected to flood

42. Study Contact Information Valerie A. Swick, EIT, PH, CFM Project Manager Flood Control District of Maricopa County vas@mail.maricopa.gov (602)506-2929 www.fcd.maricopa.gov