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Water Well Design August 6, 2015 AL/MS AWWA

Water Well Design August 6, 2015 AL/MS AWWA. Ralph Hayes, P.E., BCEE Engineering Director MSDH, Bureau of Public Water Supply. Water Well Design. -Why drill a water well? -How to get started. -Where to drill a water well -Steps in drilling a water well. Why Drill a Water Well.

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Water Well Design August 6, 2015 AL/MS AWWA

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  1. Water Well Design August 6, 2015AL/MS AWWA Ralph Hayes, P.E., BCEE Engineering Director MSDH, Bureau of Public Water Supply

  2. Water Well Design • -Why drill a water well? • -How to get started. • -Where to drill a water well • -Steps in drilling a water well

  3. Why Drill a Water Well --usually when someone decides they need more water, or a more dependable water supply. Longer Run Times- if consistent run times of 12 hrs + Average Well Life- if average well service life is high, expect failures to occur more frequently Back up Supply- if lose water service, need supply to bring plant or factory down

  4. How to Get Started • MUST DETERMINE -- How much water needed (maybe need 2 wells) -- Where is water needed (have it close to demand point) - What quality? ( potable or process water)

  5. How to Get Started • First Round Considerations • -Once preliminary considerations are resolved, the investigation begins. The question now is, can you get the amount of water needed, delivered to where it is needed, in the quality needed.

  6. How to Get Started • Resources to help determine the likely availability of water……….. • DEQ, with location can get other wells in area • Well Driller, can get specific data of existing wells in area • MSDH, Bureau of Public Water Supply • USGS, or USGS Retired

  7. How likely is water available • Take collected data, interpolate between wells to determine “expected” well depth, static water level, well yield.

  8. Sample Example • For this discussion, we will estimate the following parameters- • --500’ to bottom of aquifer • --aquifer thickness is 60 feet • --pump rate needs to be 500 gpm

  9. Test Hole • A Test Hole is a pilot hole drilled to expected Total Depth (TD) of the well, expecting to penetrate the aquifer completely. Sand samples are collected and an e-log is run on the Test Hole. • Sand Sample when analyzed, help determine the slot size of the well screen. • E-log determines where the top and bottom of the screen begin and end.

  10. Electric Log

  11. E-log, marked up

  12. Test Well • A Test Well is a small diameter (4” -6”) well and screen, set in the “sands” seen from the e-log and a pump capable of pumping 100-200 gpm. • The Test Well is set and developed and pumped until a representative sample is collected and tested.

  13. Sample Test Well Results • 1

  14. Test Well • Pro- get good idea of water quality before making permanent well. • Con- 20-40 feet of screen might not cover entire aquifer and water quality might be different in areas not screened • Com- pump rate of 100-200 gpm usually significantly less that permanent pump rate, • Chance of 500 gpm pump producing turbidity

  15. Permanent Well • Ream Test Hole and set & cement casing to top of water bearing sands. • Under ream sand zone (below casing) and set screen/lap, gravel

  16. Casing • Have to determine if you want Foreign or Domestic Pipe, (foreign typically cheaper). • Have to determine if you want Prime (w/mill certs) or Structural grade pipe, (Prime is more expensive). • Determine if welded or threaded joints, welded is the standard. • Specify pipe must have factory bevel, not torch cut

  17. Setting Casing • 1

  18. Welding Casing • 1

  19. 2-Piece Well

  20. We Drawing • 1

  21. Well Screen • Typical well screen is referred to “Stainless Steel Wire Wrapped Rod Base Screen” • Typical in 20’ or 10’ sections • Slot size determined from info obtained in TH

  22. Stainless Steel WW Rod Base • 1

  23. Drill Rigs • 1

  24. Drill Rig

  25. Mud Pits, Mud Pump • 1

  26. Drill Rig

  27. Finished Water Wells • Various ages

  28. Well w/ Generator • 1

  29. Tight Location • 1

  30. What I have run across in 30 years • Bid Form, what a Contractor likes to see…… -Test Hole to specific depth, +/- on depth, include in TH site prep • Test Well to a general depth range, +/- for additional Test Wells • Perm Well, +/- to specific well depth (Bot of screen is TD • Screen length specific, +/- for adjustments

  31. Continue • Control Panel & Electrical • SCADA System • Generator • Above Ground Piping • Tie-in to system • Chemical Feed Equipment & Building • Fence, finished site work, gravel driveway

  32. What I have seen: • Bid Forms with 40-50 line items • Bid Forms with one (1) line item • Ideal BF should have about 10 line items • Requirements saying a well must be made in the original TH or Contractor will not get paid, (old Water or No Pay)(this is outdated)

  33. More: • Requirements Contractor must guarantee water quality (only Mother Nature knows what the water quality is)

  34. Questions ? • Ralph Hayes • Ralph.Hayes@msdh.state.ms.us • 601-576-7518

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