Texas-based Chevron Pipe Line Co. has been at work on the cleanup since March 19, the day after the 1950s-vintage pipe began to leak diesel fuel from the 760-mile line and a few weeks before migration season got underway at the nearby refuge.
The camping and picnic areas have been closed ever since, and South Marina facilities were opened early to accommodate visitors.
So far, the only wildlife that has been reported to be affected has been a few ducks, some fish and six beavers, whose lodges help slow the diesel's seepage into Willard Bay. Those beavers continue to be treated at the Wildlife Rehabilitation Center of Northern Utah.
On Friday, officials reported: "Sampling data continues to indicate there is no long-term or short-term threat to human health or the environment in Willard Bay."
The Unified Command, which oversees the cleanup, is comprised of the petroleum company, the state water-quality office and the U.S. Environmental Protection Agency. The U.S. Transportation Department's Pipeline and Hazardous Materials Safety Administration continues to investigate the leak, which is the third major rupture in a Chevron line in Utah in three years.
The officials said cleanup crews continue to remove contaminated soil and take steps to control erosion. Their goal is to restore the wetlands and the park by early June.
When asked for details about the upcoming water-pressure test, Chevron spokesman Gareth Johnstone offered, "No further details at this time."
The pipeline transports diesel from Utah's five refineries to Idaho and Washington. Its split section does not appear to have failed because of pressure-cycle induced fatigue, selective seam corrosion or stress corrosion cracking, according to preliminary reports the company has made to the federal oversight agency.
"While this metallurgical information is preliminary," the agency said in approving the restart proposal Thursday, "we have considered it in our evaluation of your hydrostatic test plan."
The federal agency agreed that Chevron should spike pressure in a 3-mile section of the pipe to 1.39 times its maximum operating pressure for 30 minutes, then maintain a steady pressure at 1.25 the maximum for another 8 hours.
Although the April 18 approval letter says the company can start testing immediately, the Unified Command said only that the testing would begin "before the end of April."
The pipeline has been operating at 80 percent of normal pressure for three weeks.