The Danger of Breathing Water Wells

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The Danger of Breathing Water Wells Powered By Docstoc
					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?
• Completed in a
  partially saturated
  aquifer

• Overlying confining
  layer present

• Completion interval
  extends above water
  level
What is a Breathing Well?

• Barometric pressure
  rises

  – Air pushed into lower
    pressure subsurface
What is a Breathing Well?

• Barometric pressure
  falls

  – Air drawn out of
    unsaturated zone
What is a Breathing Well?

• Oxygen depleted air
  blown out during
  exhaling periods
Well Pits
• Cold winter air
  freezes well water

• Pits below frost line
  prevent freezing

• Hazard in confined
  space
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
    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)
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
  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
Staudinger Well
    Results
Staudinger Well
Barometric Pressure (BaroP)
and Oxygen Distribution




               Methane
BaroP and Oxygen Distribution
Daily Change in BaroP and O2
• Positive linear
  correlation between
  BaroP and oxygen
  change

• During exhaling
  periods, O2
  concentrations drop
Daily Change in BaroP and CO2
• Inverse relationship
  between BaroP and
  carbon dioxide

• During exhaling
  periods, CO2
  concentrations rise
 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!!!
“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
Inhaling Periods
• Atmospheric air
  drawn into confined
  unsaturated zone

• Oxygen consumed:
  – Microorganisms
  – Oxidation of pyrite

• Carbon dioxide
  produced
Exhaling Periods
• Subsurface air blown
  out of well

• Denitrification of
  commercial
  fertilizers

• N2 released from
  water, diluting
  remaining O2
Breathing Well Distribution
• Consistent results found
  at other monitored sites:
  – Ammeter
  – Onoway
  – Delburne

• Breathing wells reported
  in:
  –   Alberta
  –   Saskatchewan
  –   Southern Ontario
  –   Central USA
  Additional
Monitored Wells
Ammeter Well (Sylvan Lake)
Onoway
Onoway
Delburne
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
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
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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posted:5/19/2012
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