Government scientists say initial tests of shallow groundwater in the Northern Plains oil patch found no evidence of contamination from an energy boom that's already seen more than 8,500 wells drilled.
But the scientists caution that the results were unlikely to pick up contamination from surface spills or leaking well casings because the water they tested was from aquifers that predate oil and gas drilling.
The U.S. Geological Survey study released Monday looked at 30 domestic water wells in North Dakota and Montana.
Researchers found no evidence of contamination by methane, saltwater brine or other drilling byproducts.
USGS hydrologist Rod Caldwell says more research is needed to assess the continuing impacts of energy development. As many as 60,000 more wells could be drilled in coming decades.
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