Research examines groundwater contamination in North Dakota

WILLISTON (AP) — Oil and gas practices that were common decades ago in the Williston Basin left behind a salty legacy that still poses problems for groundwater and is the focus of ongoing research by the U.S. Geological Survey.

A recent study by the Geological Survey shows it could take several hundred years before the salt concentration in groundwater near at least one longtime oil- and gas-producing area returns to normal levels.

Brine makes its way up to the earth’s surface when oil and gas is extracted. Today, that saltwater is injected back underground for storage. Decades ago, brine was dumped into temporary “reserve” pits at well sites or at central collection facilities known as “evaporation” pits.

“They would pump out the water at the end and leave behind a saline slurry and backfill it, burying a large amount of salt,” Geological Survey geologist Todd Preston said.

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