Effluent from an abandoned gas well affects benthic macroinvertebrates in Big Creek, Norfolk County

Natural gasHealth Risk - Do Not Enter Sign reservoirs were first discovered in Ontario in 1866, and drilling to extract the new source of energy began in the early 1900s. Since then, thousands of natural gas wells have been drilled in southwestern Ontario. As extraction became inefficient due to the depletion of gas reservoirs, many of these wells were abandoned. Most wells abandoned before the 1970s were inadequately plugged to the standards of the time. These well plugs have deteriorated over time, causing untreated effluent, which contains contaminants such as hydrogen sulfide, to pollute the air and leak into local soils and streams. Nearby residents have been cautioned of life-threatening concentrations of hydrogen sulfide and they have noticed a strong rotten egg odour and experienced watering eyes, headaches, and nausea characteristic of exposure to hydrogen sulfide.  Residents are concerned for their safety and impacts to the environment.

The goal of this preliminary study, supervised by Dr. Simon Courtenay (UW SERS) and Dr. Mark Servos (UW Biology), was to investigate the effect of one leaking natural gas well in Norfolk County, Ontario on fish and benthic macroinvertebrates in Big Creek. Big Creek, the largest sub-watershed in the Long Point region of Lake Erie, is a cold-water stream renowned for Rainbow, Brown and Brook Trout fishing and is important habitat for species at risk. In the fall of 2019, benthic macroinvertebrate communities were sampled upstream, at the discharge site, and 200 m downstream of the effluent discharge from the leaking well into Big Creek. The upstream site acted as a reference site while the downstream site was sampled to help determine the extent of impacted area. It was hypothesized that biotic communities would differ as a function of proximity to the gas well discharge. Benthic macroinvertebrate communities at the upstream and downstream sites had significantly higher proportions of pollution-sensitive taxa when compared to the discharge site, indicating a decline in water quality. SERS Adjunct Professor Brian Craig

These results suggest that the liquid effluent from this natural gas well is affecting the local biota of Big Creek and more research in this and other creeks of Norfolk County is warranted. Until possible impacts are more thoroughly investigated, the precautionary principle should be applied throughout decision-making, as the lack of scientific certainty should not be used as a reason to postpone mitigation measures. Unfortunately, the cost of capping abandoned natural gas wells in Ontario falls on the landowner if no well operators are found to be responsible. With other abandoned natural gas wells in Norfolk county costing up to $500,000 to cap, most landowners do not have the funds to seal wells. Our research will become increasingly important as the number of leaking abandoned gas wells increases due to the deterioration of well seals.

For more information: