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Converting a supply well into an ASR well: Case Histories

Converting a supply well into an ASR well: Case Histories. Roger Dittus PG – United Water Idaho Inc. United Water Idaho Serving Boise area Several pressure zones 80+ supply wells Two surface water treatment plants. Idaho. Boise. ?. Conceptual Cross-Section (Regional Scale).

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Converting a supply well into an ASR well: Case Histories

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  1. Converting a supply well into an ASR well: Case Histories Roger Dittus PG – United Water Idaho Inc

  2. United Water Idaho • Serving Boise area • Several pressure zones • 80+ supply wells • Two surface water treatment plants Idaho Boise

  3. ? Conceptual Cross-Section (Regional Scale) Shallow coarse-grained sediments and basalt W E Municipal 4,000 2,000 2,000 4,000 Municipal Domestic Interbedded sand, silt, clay ? Elevation (feet) Fine-grained Sedimentswith sand lenses Mudstone 0 ? VolcanicRocks ? ? Adapted from cross section by S. Wood, BSU Geosciences C. Petrich

  4. Uranium > MCL ARSENIC > MCL Most problematic Manganese &Iron

  5. Settlers well Swift well Maple Hill 2 well Mn U Market St. well U United Water ASR projects United Water ASR projects As

  6. Piping Tee 10-inch to 4-inch Cla -valve Flow Meter Flow During Injection

  7. History of Swift Well: Looking for a Solution: Well Drilled in 1978 1986 to 1992: increase from 0.04 mg/L to 0.53 mg/L 1992 to 1996: increase from 0.53 mg/L to 0.94 mg/L 1997: tried to drill out of manganese but deeper water unacceptable United Water Idaho’s first ASR Well

  8. 6-inch Private Well in vicinity of Swift well limits injection rate

  9. Swift 1 Mn vs. % recovery

  10. Swift 1 Mn vs. % recovery

  11. Swift 1 Mn vs. % recovery

  12. Loss of well efficiency during injection

  13. injected v. recovered water Swift Well 1 Swift well Increase pump capacity

  14. Shallow Aquifers Shallow-Intermediate Aquifers Vertical Extent of GW-SW Interaction SW NE Terrace Gravels Boise River MediumTDS Low TDS Elevated Uranium High TDS Low TDS Deep Aquifers (Conceptual Model) C. Petrich

  15. Settlers Well: Native Water has 40 ug/L Recharge water source: groundwater – mix from two wells Maple Hill 2 Well: Native Water has 42 ug/L Recharge water source: deep groundwater Used as non-peak season supply while treatment system shut down

  16. Pilot-testing two wells with elevated uranium

  17. Pilot-testing two wells with elevated uranium

  18. Uranium trend for pilot tests

  19. Maple Hill 2: Estimated Mixing of native and injected Water 50% Native Water Native Water 25% Native Water 10% Native Water Recharge Water 51 Million Gallons

  20. Maple Hill 2 well: D.O. in recovered water Dissolved Oxygen in Recharge Water = 0.25 mg/L

  21. Screened Interval and Injection v. Recovery Rate Settlers well Maple Hill 2 well 85 % Recovery 100+ % Recovery 200- 230 GPM 800 GPM 200 - 230 GPM 175 - 400 GPM 47 FT 92 FT

  22. Market Street Well: primary recharge water source has some arsenic Native Water has 13 ug/L arsenic

  23. RECHARGE RECOVERY Multiple completion intervals Potential for preferential recharge in some zones Pumping rate greater than recharge rate may draw in native water with arsenic 500 feet 1 2 3 4 5 6 900 feet 7

  24. Pre-ASR Arsenic concentration Injection rate = 270 gpm Storage Time = 5.9 days Recovery Rate = 775 gpm

  25. Second Test Injection rate = 270 gpm Storage Time = 4.2 days Recovery Rate = 665 gpm

  26. Third Test Injection rate = 290 gpm Storage Time = 5.1 days Recovery Rate = 690 gpm

  27. Market St. well ASR • Pilot testing indicates ASR may be feasible • 100% recovery may not be possible • Distribution system manipulation to improve recharge source water/ ASR compatility may be worthwhile • Based on nearby ASR testing: after 1-2 weeks Trihalomethanes increase in this aquifer but decrease to original levels after 2 months storage • Currently storing 15 MG (ten times test volume) for first “production test” of this well

  28. Summary & Conclusions • Prior to ASR, several United Water Idaho Supply wells were unusable due to their water-quality • Small-scale ASR test results may only give a rough approximation of actual operations-scale ASR results • ASR at most locations where it has been implemented has proved feasible • ASR wells are more trouble than regular supply wells • Overall, ASR has been cost-effective

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