BISMARCK, N.D. (AP) — Regulators are monitoring tests to determine if an oil field spill near Williston has tainted drinking water sources in the area, the North Dakota Department of Health said Tuesday.
Denver-based Zavanna LLC told regulators a faulty valve caused a spill of more than 114,000 gallons of oily saltwater at a well site about 4 miles northeast of Williston on Sunday.
State environmental scientist Bill Suess said crews will bore holes in the area to see if the spill reached groundwater supplies. Some private drinking water wells also are being tested as a precaution, he said.
Williston’s drinking water is safe because the city draws its water from the Missouri River, Suess said.
The company, which did not immediately return telephone calls for comment on Tuesday, planned to excavate spill-tainted soil, Suess said. Two state inspectors were on site Tuesday, he said.
Suess said the company had a berm around the oil well site but it wasn’t adequate to contain the spill, which contained so-called produced water, a mixture of saltwater and oil that can contain drilling chemicals.
“It either flowed over the berm or there was a bad spot in the berm and it went through it,” Suess said. “A better berm would have kept it on the pad.”
North Dakota regulators last month proposed a spate of new rules aimed preventing spills, including one that would require berms of at least a foot high to be built around a well site.
Public hearings on the proposals will be done in several cities in April. Regulators have said October is the earliest the rules could be in place.
Suess said Zavanna has had 55 oilfield spills since 2012, including 20 spills that migrated from the well site.
Zavanna last month paid a $69,000 penalty for a March 2014 oil spill near the confluence of the Yellowstone and Missouri rivers. Regulators said a company oil well was swamped by floodwaters with water that backed up in the ice-choked channel. An unanchored tank floated at the well site and broke a valve, spilling about 1,400 gallons of oil.
Most of the spill was contained by booms as floodwaters receded, but the oil coated brush, trees and grass in the area, regulators said.
Records show there have been 233 oil field spills so far this year in North Dakota, including 72 that have left the well site.
In 2015, there were 1,635 spills reported, including 495 that were not contained at the well site. That was down from a record 2,184 spills in 2014, including 631 that were not contained, data show.
“Everything is kind of improving because of the oil slowdown and because companies are getting better,” Suess said. “But they still have a long way to go.”
Copyright 2016 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.