This slideshow gives information about the variety of options studied by Gannett Fleming on the dam technology choices for Tempe Town Lake. More information can be found at www.tempe.gov/lake and click on Dam Replacement in the blue box in the upper right hand corner of the webpage.

1. Tempe Town Lake Downstream Dam ReplacementALTERNATIVES EVALUATION UPDATE IRS Tempe City Council September 22, 2011

3. Project Update with Council – September 22

4. Phase 1 Validate Concept & Select Dam Technology – November

5. Phase 2 Design New Dam – August 2012

6. Acquire Permits – July 2013

7. Bid and Procure Construction Contract – October 2013

8. Fabricate New Dam – November 2014

9. Construction Complete – December 28, 2015** Per current agreement with Bridgestone.

10. Town Lake: Part of a River System Granite Reef Dam Watershed Map

11. Town Lake: Part of a River System Salt River Watershed Schematic Diagram Tempe Town Lake Dam

12. Current Level of Flood Protection Designed to maintain or improve current levels of flood protection – 210,000 cubic feet per second (cfs.) This is consistent with the rest of the river system.

14. Handle Flows from Storms, Regular Water Sources

15. Return Lake to Normal After Floods

16. Handle Water from Extreme Flood Events Smaller Than 210,000 cfs

17. Meet Regulatory Requirements

19. Regulatory Conditions

21. West Dam 200-Year Discharge: 204,000 cfs

22. East Dam 200-Year Discharge: 207,000 cfs

24. Bascule or Bottom-Hinged Leaf Gates

25. Inflatable Rubber Dams (water and air-filled)

26. Ogee Crest Weirs

27. Labyrinth Weirs

28. Many Styles of Fuse Plugs

29. Several Styles of Pneumatically-Operated Hinged Crest Gates (Obermeyer)

30. Hydraulic Hinged Crest Gates

31. Dyrhoff Rubber Dams (Sumitomo)

32. Vertical Lift Gates

33. Swing Gates

34. Fusegates (Hydroplus)

35. Earth Embankment/Fuseplug

36. Several Styles of Mixed-type Spans

37. Cable-Operated Hinged Crest Gate

39. Concrete dams in outer spans and gates in inner spans

41. Results of Restricted Flow Results of Mixed Type Alternative that Impedes Two Spans

43. Zoned earth and rockfill embankment with a sloping impervious core

45. Alternatives Carried Forward Obermeyer Crest Gates Fusegates Hinged Crest Gates Inflatable Rubber Dams 1 2 4 3

47. Inflated by pumping air or water until height is reached

57. Dam Budget Minus $367,000 Gannett Fleming Contract for Dam Technology Analysis

59. Includes Design, Materials, Construction

60. Does Not Include East Dam or Pump System

61. Finance Options Include:Use Remaining $3,633,000 Seek Voter Approval for Bond Authorization for Dam Replacement Capital Costs Sale of City Properties Combinations

63. Failure Modes and Effects Analysis

64. Third Party Review

65. Gannett Fleming, Staff Will Recommend Dam Technology

66. Review Financing Options