An about 200-barrel oil pipeline leak in February - about one mile from Lake Sakakawea in the Little Missouri National Grasslands - that was thought to have been cleaned up adequately, may not have been.

High concentrations of groundwater contamination have been found in a drainage area in the Charlson area where the released oil and saltwater ended up after flowing about 7/10 of a mile over frozen ground, said Larry Melvin, minerals and geology program manager of Dakota Prairie Grasslands, a division of the U.S. Forest Service.

He said as far as he knows now, the contamination is still "over a mile away" from Lake Sakakawea. But he said holes, which were dug near a 10-yards-in-diameter catch pit that was excavated in February to contain the spill, also show contamination and it's not known yet how much farther, if at all, that contamination has migrated.

He said it's possible the contamination found in the drainage could have been from an old spill even decades ago when there weren't many regulations. But he said the contamination is probably from the February leak. And when test results received about one week ago showed there was groundwater contamination to a depth of 8 to 10 feet, the forest service notified the North Dakota Department of Health.

"I'd call that significant," said Kris Roberts, an environmental geologist with the Department of Health's division of water quality, about the size of the spill. He will meet Wednesday on site with an environmental consultant and others.

Melvin said the estimated amount of oil and salt water, 200 barrels, was based mainly on the drop in the well's production.

He said the company that owns the well, Petro-Hunt L.L.C. of Dallas, notified his department on Feb. 22, the same day that personnel in a Tesoro Corp. plane flying over the pipeline area discovered the leak when they saw a geyser of oil erupting from the pipeline.

Melvin said that the leak happened when the ground was frozen and so Petro-Hunt personnel thought they had the spill contained by doing several things:Creating a drainage pit Feb. 24 to remove contaminants; controlled burns at the spill site on Feb. 26; and then flushing the area Feb. 28 with 500 barrels of fresh water.

"Petro-Hunt is doing a very good job of cleaning this up," Melvin said.

The spill site is about a dozen miles northeast of Keene in Section 3 of Township 153 North and Range 95 West, accessed only by an old oil-service road in the area.

"It's a really rugged area," said Mark Bohrer, petroleum engineer for the North DakotaIndustrial Commission, Oil and Gas Division, which will oversee clean-up and remediation along with the health department.

He said the pipeline heads northwest from the well. The leak occurred about two-thirds of a mile northwest of the well. The storage tank where the oil was heading was another quarter-mile away.

The released mix of oil and salt water traveled south about 7/10 of a mile to a narrow drainage area - a dry draw. There's no creek in the area, he said. He said he doesn't have information yet on the size of the drainage or how long it will take to finish clean-up efforts. "A lot of clean-up has already taken place."

Melvin said he thinks that area is leased for grazing and that this situation won't affect this season's grazing. He said Petro-Hunt would be responsible for fencing off any possible hazards - such as holes dug by front-end loaders.

Melvin said he expects, unfortunately, for more leaks to happen in the Charlson area because of increased oil activity where pipeline infrastructure is more than 50 years old.

He said in the fiscal year, since Oct. 1, 2007, there have been 57 leaks in the national grasslands, so far, ranging from a half barrel to this 200- barrel situation. And he expects by fiscal year's end, Sept. 30, the total spill number will beat the previous fiscal year's total of 88 spills.

"I hope not, but realistically that probably going to happen,"he said. "That's one target I don't want to hit."

The worst spill in the previous fiscal year occurred Jan. 4, 2006, when a plume of salt-water contamination killed all the fish in the upper reaches of Charbonneau Creek.

According to past reports, about 22,000 barrels of toxic water leaked from a broken pipe in Zenergy Inc.'s oil field west of Alexander Jan. 4. The toxic water comes up with oil and is piped or trucked to injection wells.

Roberts said that a couple months ago, the creek was released from further monitoring.

"The creek has been cleaned up ... We don't anticipate any further problems," he said.

And he said any saltwater that reached the Yellowstone River was so diluted that it wasn't a threat.

(Reach reporter Virginia Grantier at 250-8254 or at virginia.grantier)@bismarcktribune.com