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White Tanks Flood Retarding Structure No. 4 Rehabilitation Contract FCD 2008C002

White Tanks Flood Retarding Structure No. 4 Rehabilitation Contract FCD 2008C002. March 12, 2007. 1. Project Watershed. 2. Project Area. 3. White Tanks #4 Project History. 1951 - August Floods (7.3”-24hr., 13.6” total storm)

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White Tanks Flood Retarding Structure No. 4 Rehabilitation Contract FCD 2008C002

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  1. White Tanks Flood Retarding Structure No. 4 RehabilitationContract FCD 2008C002 March 12, 2007 1

  2. Project Watershed 2

  3. Project Area 3

  4. White Tanks #4 Project History • 1951 - August Floods (7.3”-24hr., 13.6” total storm) • 1954 - White Tanks FRS No. 4 built by Soil Conservation Service (SCS) now NRCS • 1979 - Crack investigation on White Tanks #4, mitigation recommended for transverse cracking • 1982 - NRCS installed granular centerline filter drain and finger drains to reduce potential for piping and seepage erosion • 1994 – Concrete inlet channel built to convey 100yr runoff to White Tanks #4 4

  5. White Tanks #4 Project History • 2003 - Phase I assessment • 2005 - Rehabilitation project begins in cooperation with NRCS as federal sponsor • 2008 – NRCS plans to complete the Work Plan and Environmental Assessment for the rehabilitation • 2008 - Final design begins 5

  6. White Tanks #4 Project Background • 54 year old earthfill flood control dam • Function was to protect agricultural lands and irrigation structures • Provides 100 year flood protection • Crest length is 6,839 feet • Structural height is 20 feet • Upstream/Downstream slopes 2:1 • Total watershed area is 20.25 square miles • Operated and maintained by the District 6

  7. White Tanks #4 Project Background • ADWR is the State jurisdictional agency • NRCS is the Federal jurisdictional agency • Dam classification: High Hazard/Small • Design requires more stringent of ADWR or NRCS criteria be used; at times FCD too i.e. hydrology 7

  8. White Tanks #4 Deficiencies • CMP outlets for principal spillways (ADWR) • CMP outlets lack diaphragm filters (ADWR) • Left spillway obstructed by farm machinery store (ADWR) • Concrete inlet channel may impact functioning of left spillway • Erosion of earthen spillways • Partially penetrating central filter 8

  9. White Tanks #4 Deficiencies • Transverse embankment cracking (ADWR) • Foundation adequacy? • Inadequate freeboard • Inability to safely pass the PMF (ADWR) 9

  10. Major Design Tasks • Data collection/Data Review • Survey, photogrammetry and mapping (1 foot), must have capability to do • Hydrology: inflow design flood (IDF): • what will it be (PMF, NRCS PSH, or something else) • Jackrabbit Channel capacity • I-10 embankment • Hydraulics: emergency spillway and principal spillway • Geotechnical investigation of site 10

  11. Major Design Tasks • Landscaping • Final design of rehabilitated structure: 30%, 60% 90% and 100% final design process • Failure modes and effects analysis (FMEA) • Value engineering • Constructability analysis 11

  12. Major Construction Tasks • Oversight of construction as the Engineer-of-Record for the project 12

  13. Important Project Issues • Project management communication • Consultant team capabilities • Identifying and resolving design issues early on in the process • ADWR coordination – ADWR permit needed • NRCS coordination – project partner, 65% reimbursement 13

  14. Important Project Issues • Maintaining project schedule • Timely and accurate invoicing • Quality deliverables 14

  15. WT #4 FRS inlet channel 15

  16. WT #4 left abutment and spillway 16

  17. CMP outlet at Sta 17+32 17

  18. Principal outlet at Sta 17+32 18

  19. Upstream side of dam looking west from sta 17+32 19

  20. ADOT borrow pit from crest of dam 20

  21. Principal outlet at sta 58+50 21

  22. CMP outlet at sta 58+50 22

  23. Future housing downstream of dam 23

  24. Avondale Wash in impoundment area 24

  25. Right spillway from left containment dike 25

  26. Sept 1970, view from left spillway @ Roosevelt Street. What do you see in the impoundment area? 26

  27. Questions? 27

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