Accessing Your Lake Water Supply During Drought Conditions

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Accessing Your Lake Water Supply During Drought Conditions presented by Brian Coltharp & Steve Watters at TWCA Annual Conference www.twca.org

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Accessing Your Lake Water Supply During Drought Conditions

  1. 1. Accessing Your Lake WaterSupply During DroughtConditionsBRIAN COLTHARP & STEVE WATTERSMarch 8, 2012 1
  2. 2. How Bad is the Drought? Mexico may export water Fort Worth Star-Telegram October 17, 2011 Drought brings toilet to tap to fore United Press International August 23, 2011 2
  3. 3. Overview• Issues that May Affect Pumping from Lake• Alternative Strategies• Permitting Issues 3
  4. 4. Issues That May AffectPumping from LakePhysical Ability for Water to get to Pump Stations Full Drought 4
  5. 5. Issues That May AffectPumping from LakeNet Positive Suction Head (NPSH)• Available (NPSHa)• Required (NPSHr) set by pump manufacturer• NPSHa = Patm + (Lake Elev. – Impeller Elev.) – Hsuct. – Vapor Press.• Margin = NPSHa/NPSHr = 1.3 or higher 5
  6. 6. Issues That May AffectPumping from LakeMinimum Submergence• Distance from water surface to suction bell• Submergence Required (from pump mfr) O  6
  7. 7. Issues That May AffectPumping from LakePumping Capacity Pump and System Curves 200 180 160 140 Pump AOR 120 Head (feet) 100 80 60 40 20 0 0 5000 10000 15000 20000 25000 30000 35000 40000 45000 Flow Rate (GPM) 7
  8. 8. Alternative StrategiesTemporary Pumping 8
  9. 9. Alternative StrategiesTemporary Pumping Considerations1. How long will I have to do this?2. Where do I need to pump to?3. What type of pumps should I use?4. How am I going to operate this facility?5. How much will it cost?6. How long will it take to implement? 9
  10. 10. Alternative StrategiesTemporary Pumping Considerations1. Time period to be in-service – Own vs. lease – Electric vs. generator2. Pump to existing structure or all the way to destination – Alleviate NPSH & submergence of existing pumps – Flow & head considerations3. Types of pumps – Horizontal – Vertical – Submersible 10
  11. 11. Alternative StrategiesTemporary Pumping Considerations4. Ease of Operations – Use of existing facilities – User friendly5. Costs – Size & number of pumps – Power requirements – Length of piping6. Schedule – Availability of power & pumps – Permitting 11
  12. 12. Alternative StrategiesDredging 12
  13. 13. Alternative StrategiesDredging Considerations1. Undisturbed lake bottom vs. silt – Availability of contractors – Permitting – Costs (recent bids $57/CY vs. $7/CY)2. Equipment considerations – 20’ to 30’ depth max for small dredge – Accessibility – Dredge power, electric vs. diesel – Noise abatement needs – Impacts on lake recreation and lake safety – Increased TSS at treatment plants during dredging 13
  14. 14. Alternative StrategiesDredging Considerations3. Cost considerations – Mob/demob large percentage – Economy of scale – Impacts of rock, stumps and logs – Distance to disposal site – Availability of dredge contractors (this is a limited community of contractors and availability can change quickly)4. Dredge disposal – Upland disposal lends to Nationwide Permit – In-lake disposal requires at least LOP – Large area, flat disposal site ideal – Control of TSS from decant water – Various disposal options – disposal pit, land application, rapid dewater 14
  15. 15. Permitting forAlternative Strategies 15
  16. 16. Permitting Authority• It’s my water, so why do I need a permit?• Waters of the U.S. – governed by the U.S. Army Corps of Engineers – Section 10, Rivers and Harbors Act of 1899 • Navigation protection – Section 404, Clean Water Act • Water quality protection 16
  17. 17. What’s Regulated• The discharge of dredged material (33 CFR 323.2) – Material excavated from waters of the United States – Runoff or overflow from a contained land or water disposal area – The redeposit of dredged material other than incidental fallback 17
  18. 18. What’s NOT Regulated• Discharges associated with onshore processing of dredged material extracted for commercial use• Activities involving only cutting or removing vegetation so that root systems are not disturbed• Incidental fallback of dredged material – the redeposit of small volumes of dredged material incidental to excavation activity…when such material falls back to substantially the same place as the initial removal (33 CFR 323.2(d)(2)(ii)) 18
  19. 19. Permitting• Good News…there are options: – Some activities are exempt – Sometimes Corps notification is NOT required – General permits (Nationwide and Regional General Permits) – Modified individual permits (Letter of Permission procedures) – Standard individual permits• Bad News – Sometimes permits require Corps notification – Sometimes multi-agency review is required – Sometimes public notice is required – It can take more time than you think 19
  20. 20. Permitting Considerations• Purpose and Need for dredging• Area and volume of dredging• Alternatives to avoid, minimize, and mitigate impacts• Who owns/operates the lake?• State-owned water body?• Dredged material disposal site• Handling of return flows• Threatened and endangered species• Historical and archeological resources 20
  21. 21. Corps Districts in Texas 21
  22. 22. Permitting• Issued in response to Texas drought• Summarizes 7 existing permitting options• Intent – to streamline authorization by informing 22
  23. 23. Public Notice Overview• “Drought conditions do not diminish federal jurisdiction”• Some permits require application or PCN• Compensatory mitigation may be required• Regional and General Permit Conditions always apply• Section 401 Water Quality Certification Conditions always apply 23
  24. 24. Permits• NWP 3(b) – Maintenance – Preconstruction notification (PCN) required for sediment removal – No volume or area limits (according to Public Notice) – Sections 10 and 404• NWP 12 – Utility Line Activities – Applicable for temporary pumping facilities – PCN required sometimes – 1/2 acre impact limit – Sections 10 and 404• NWP 16 – Return Water from Upland Contained Disposal Areas – PCN and individual 401 certification required – 300 mg/L TSS limit – Section 404 24
  25. 25. Permits• NWP 19 – Minor Dredging – No PCN – Maximum volume = 25 cy – Sections 10 and 404• NWP 35 – Maintenance Dredging of Existing Basins – Sediment removal around existing marinas, boat docks, etc. – No PCN – Dredging limited to previously authorized depth of basin – Section 10 25
  26. 26. Permits• Regional General Permit (RGP) 2 – Utility Lines and Intake and Outfall Structures – Allows for temporary structures to operate existing intake facilities – PCN required – 1/4-inch mesh intake screen, 1/2 ft/second max intake velocity – Sections 10 and 404• RGP 8 – Boat Ramps and Minor Facilities – 200-ft dredging limit – PCN triggers: • 1/10-acre PCN limit • Impacts to forested wetlands • Sediment return flows to waters of U.S. – Sections 10 and 404 26
  27. 27. Permits• LOP 1 - Letter of Permission Procedure for Activities at Certain Reservoirs and Federal and State Sponsored Projects – Allows sediment removal and other activities – Application letter required – Agency consultation typical – Sections 10/404• LOP 2 - Letter of Permission Procedure for Excavation Activities – Allows sediment removal, primarily – Application letter required – Agency consultation typical – Sections 10/404 27
  28. 28. Permits• Programmatic General Permit-2 (PGP-2) - Activities Authorized by Lower Colorado River Authority Lakewide Permits – Allows dredging during lakewide drawdowns. – Apply to LCRA 28
  29. 29. Permit Timing• After PCN/application filing: – NWPs w/o PCN – good to go immediately – NWPs with PCN – allow at least six weeks – RGPs – allow at least six weeks – LOPs – allow at least eight weeks, often more – Standard IP – allow at least six months 29
  30. 30. Accessing Your Lake WaterSupply During DroughtConditionsBRIAN COLTHARP & STEVE WATTERSMarch 8, 2012 30

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