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The Danger of Breathing Water Wells

The Danger of Breathing Water Wells . Sarah Hill and Carl Mendoza Department of Earth and Atmospheric Sciences University of Alberta. Outline. What is a breathing well? The silent killers Objectives Methods Results Conclusions. What is a Breathing Well?.

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The Danger of Breathing Water Wells

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  1. The Danger of Breathing Water Wells Sarah Hill and Carl Mendoza Department of Earth and Atmospheric Sciences University of Alberta

  2. Outline • What is a breathing well? • The silent killers • Objectives • Methods • Results • Conclusions

  3. What is a Breathing Well? • Completed in a partially saturated aquifer • Overlying confining layer present • Completion interval extends above water level

  4. What is a Breathing Well? • Barometric pressure rises • Air pushed into lower pressure subsurface

  5. What is a Breathing Well? • Barometric pressure falls • Air drawn out of unsaturated zone

  6. What is a Breathing Well? • Oxygen depleted air blown out during exhaling periods

  7. Well Pits • Cold winter air freezes well water • Pits below frost line prevent freezing • Hazard in confined space

  8. A Disturbing History 1922 • Two men died in hand dug well (66 ft) east of Red Deer • Deaths attributed to a “black damp gas” 1970 • A couple died in a well pit east of Delburne • Well confirmed as a breathing well • No mention of what gas present in pit

  9. The Staudinger Story 1999 • Two teenagers died of asphyxiation after losing consciousness in their farm well pit near Sylvan Lake • Gas analysis of air from the pit: • low oxygen (8.7%) • excess nitrogen gas (>90%) • Low pressure period prior to deaths Vancouver Sun (August 14, 1999)

  10. Objectives • Investigate the physical relationship between barometric pressure and oxygen-depleted breathing water wells • Determine the cause of oxygen depletion in the unsaturated zone of the partially saturated aquifer

  11. Methods • Continuous air monitoring: • Barometric pressure • Air flow rate • O2, CO2, CH4 • Groundwater samples: • Water chemistry (field and lab) • Presence of various bacteria • Oxygen-18 and Deuterium isotopes

  12. Staudinger Well Results

  13. Sylvan Lake Medicine River Staudinger Well

  14. Methane Barometric Pressure (BaroP) and Oxygen Distribution

  15. BaroP and Oxygen Distribution

  16. Daily Change in BaroP and O2 • Positive linear correlation between BaroP and oxygen change • During exhaling periods, O2 concentrations drop

  17. Daily Change in BaroP and CO2 • Inverse relationship between BaroP and carbon dioxide • During exhaling periods, CO2 concentrations rise

  18. Elevated Nitrogen • Denitrification • >10 mg/L NO3 in shallow groundwater • <0.3 mg/L NO3 in deeper groundwater • Moderate levels of denitrifying bacteria detected • Evidence of excess N2 • Water in equilibration with air = 17.7 mg/L (78%) • Staudinger groundwater contains over 20 mg/L of N2 • 20 mg/L »90% Nitrogen gas!!!

  19. “Pop bottle effect” • Excess dissolved gas • 112 to 115 % • High BaroP • High gas solubility • N2 remains in solution • Low BaroP • Decrease solubility • Gases exsolve from solution

  20. Inhaling Periods • Atmospheric air drawn into confined unsaturated zone • Oxygen consumed: • Microorganisms • Oxidation of pyrite • Carbon dioxide produced

  21. Exhaling Periods • Subsurface air blown out of well • Denitrification of commercial fertilizers • N2 released from water, diluting remaining O2

  22. Breathing Well Distribution • Consistent results found at other monitored sites: • Ammeter • Onoway • Delburne • Breathing wells reported in: • Alberta • Saskatchewan • Southern Ontario • Central USA

  23. Additional Monitored Wells

  24. Ammeter Well (Sylvan Lake)

  25. Onoway

  26. Onoway

  27. Delburne

  28. Conclusions • Breathing water wells inhale or exhale “air” as barometric pressure varies over time • These wells have been linked to a number of deaths • Incoming oxygen consumed by microorganisms, producing carbon dioxide • Excess N2 gas, produced during denitrification, dilutes the remaining subsurface gas

  29. Conclusions • Understudied in Earth sciences • Not freak geological occurrences, but common across North America • Public Awareness • Important to inform those who live in prone areas or already own such wells • Falling water levels – potential for more of these wells

  30. Acknowledgements • Staudingers and other landowners • Canadian Ground Water Association • Hydrogeological Consultants Ltd. • Natural Sciences and Engineering Research Council of Canada • Geological Society of America • Prairie Farm Rehabilitation Administration

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