A new evaluation of groundwater in the Williston Basin oil production area of Montana found the energy production activities have not affected shallow groundwater quality.
The study looked at concentrations of a number of chemicals found in the groundwater, and compared them to health-conscious drinking water standards and evaluated for methane content, the U.S. Geological Survey (USGS) reported. To make their findings the team looked at 30 randomly distributed, non-federal domestic wells screened in the upper Fort Union Formation.
"These results are good news for water users, and the data provide a valuable baseline against which future water-quality data can be compared," said Peter McMahon, a USGS hydrologist and lead author of the study. "However, it is important to consider these results in the context of groundwater age."
Based on carbon-14 dating, most of the tested water was about 1,000 years old and originated before the oil boom occurred in the region. The researchers chose this approach because shallow wells are more effective for detecting contamination caused by recent surface spills than domestic ones.
This groundwater could be contaminated by subsurface leaks released by poorly cemented oil or gas wells, but groundwater velocities calculated from the carbon-14 ages would have moved far from their original source at this point and more research is needed to make a full assesment.
"The groundwater age results indicate that a long-term commitment to monitoring is needed to assess the effects of energy development on groundwater quality in the Williston Basin production area," McMahon said.
The study was the "first comprehensive regional assessment of shallow groundwater quality and age in the Williston Basin production area." This is also the first time the effects of energy development on groundwater quality have been determined groundwater-age measurements; the new approach help lead to more effective monitoring processes in the future.
While regulators working in North Dakota receive several spill reports every day, Karl Rockeman, director of the water quality division within the North Dakota Health Department, told the News Tribune. Despite the potential danger, most of these spills are dealt with quickly before they have a chance to contaminate groundwater. As many as 60,000 more wells could be drilled in the Northern Plains in the near future.
"Companies in general are doing a better job of preventing and mitigating spills to keep them as small and have as minimum an impact as possible," Rockeman told the News Tribune.
The findings were published in a recent edition of the journal Groundwater.
