CHARACTERIZING THE ROLE OF BAROMETRIC PRESSURE IN OXYGEN–DEPLETED BREATHING WATER WELLS

Breathing water wells are wells completed within partially saturated aquifers, below perched or low conductivity zones, where the completion interval extends above the water level. Changes in barometric pressure lead to air pressure gradients between the atmosphere and the subsurface, driving gases either into, or out of, the well. During low barometric pressure events, air blown out of these wells is commonly depleted in oxygen. In July 1999, two teenagers died of asphyxiation near Sylvan Lake, Alberta, because of low oxygen concentrations in the air emitted from the breathing water well on their farm. This study was conducted to investigate the link between oxygen-depleted breathing water wells and barometric pressure fluctuations.

Barometric pressure, well air-flow rates, and oxygen and carbon dioxide concentrations were monitored for a year at several breathing wells in Central Alberta. Water quality and stable isotope analyses were conducted for each well. Results show that changes in oxygen and carbon dioxide concentrations are significantly correlated to changes in barometric pressure. During periods of rising or stable barometric pressure events, oxygen concentrations are at, or near, atmospheric levels; however, oxygen concentrations drop, to a minimum of 4%, within hours of a decrease in barometric pressure. The behavior of carbon dioxide is opposite to that of oxygen but dampened in magnitude, rising above 3000 ppm during low barometric pressure events. Groundwater chemistry, and oxygen-18 and deuterium analysis of the water, verified that these wells are in groundwater recharge areas and the water is oxygen deficient. These data suggest that any oxygen reaching the variably saturated aquifer is consumed by organic and inorganic reactions, being partially transformed to carbon dioxide. These results highlight the risks associated with such wells, and emphasize the need for proper well completions in areas prone to such behavior.