By Kristen Hays
HOUSTON (Reuters) - Exxon Mobil Corp on Wednesday was digging out oiled lawns to replace them with fresh sod in an Arkansas neighborhood where a crude oil pipeline ruptured last week, but the line remained shut with no estimate of when it would restart, the company said.
While response crews had begun removing oiled dirt and grass around houses in the subdivision, a plan to excavate the area around the pipeline breach remained under development for U.S. regulators' review.
The company's Pegasus pipeline, which can transport more than 90,000 barrels per day of Canadian crude oil to Texas from Illinois, ruptured on Friday in the subdivision in Mayflower, Arkansas, about 20 miles northeast of Little Rock.
Exxon told the U.S. Transportation Department's Pipeline and Hazardous Materials Safety Administration (PHMSA) that the company estimated 3,500 to 5,000 barrels of crude leaked, but the company has not yet qualified its publicly released estimate of several thousand barrels.
PHMSA noted Exxon's specific estimate in a corrective order the agency issued late Tuesday that requires Exxon to develop a pipeline restart plan, test the damaged part of the line and get regulatory approval to restart post-repair.
PHMSA's order said Exxon learned of the problem when pressure dropped in the pipeline, and had shut valves on either side of the breach within 16 minutes.
Crude bubbled up to the surface and leaked onto residential lawns and streets and into storm drains. Local responders quickly built dikes to block it from reaching nearby Lake Conway, a popular fishing lake, before Exxon crews had mobilized to put booms on the water as a precaution.
"They saved the lake with that effort," Ed Barham, spokesman for the Arkansas Department of Health, told Reuters on Wednesday.
Exxon spokesman Alan Jeffers said on Wednesday that the lake remained free of oil.
Allen Dodson, Faulkner County Judge in the county that houses the subdivision, said the dikes built from dirt and rock "held strong" in the rain.
"We've shored them up over time. Response is going well," he said on Wednesday.
Twenty-two affected homes evacuated shortly after the rupture remained empty on Wednesday as Exxon and U.S. Environmental Protection Agency crews continually monitored air quality in the subdivision, Barham said.
The state's health department, which will give the final approval for affected residents to return to their homes was evaluating air quality data collected by both crews. Barham said levels of benzene and other compounds that accompany crude oil have "come down steadily since the beginning," but evacuation orders remained in place.
"The situation is improving rapidly and they are moving quickly," he said of Exxon's cleanup efforts. "At the very least in a phased way, some or most of those people can go home pretty soon."
He declined to specify if pretty soon meant this week, the weekend, or later, noting that rain in the area may lengthen cleanup that could be faster in good weather.
Exxon also said on Wednesday that its contractor, U.S. Environmental Services, has a wildlife rehabilitation operation on site.
So far the oiled animals those crews have worked with include 16 ducks, seven turtles, nine reptiles, a beaver and a muskrat. Seven ducks have been found dead, the company said.
(Editing by Bob Burgdorfer)