When ExxonMobil's Pegasus pipeline ruptured on March 29, the company announced that no oil had leaked into Lake Conway, a major recreational reservoir just nine-tenths of a mile from the spill site in central Arkansas.
Some oil had spilled into a "cove adjacent to" the lake, the company said, but "Lake Conway remains oil free," according to news releases Exxon issued as recently as April 5.
That position has sparked a debate over where Lake Conway—one of Arkansas' premier fishing spots—begins and ends.
Arkansas Attorney General Dustin McDaniel told reporters, "I don't understand where this distinction is coming from. ...The cove is part of Lake Conway."
On Saturday, Exxon acknowledged that subtlety for the first time. "There is no oil in the main body of Lake Conway," according to a news release on Apr. 6—and an Exxon spokesperson on Tuesday.
The cove in question is a boomerang-shaped lowland swamp that spans 30 acres along the southern tip of the 6,700-acre, man-made lake. Tiny streams carried diluted bitumen from Canada's oil sands region into the cove from the spill site in Mayflower, Ark., about 20 miles northeast of Little Rock. Dilbit is the same type of oil that would flow through the proposed Keystone XL pipeline.
The swampy area is separated from the main lake by State Highway 89 but connected by a pair of 48-inch metal pipes. Those pipes—called culverts—run under the road and drain excess water from the cove into the lake, so water doesn't spill over onto the highway.
After the spill, emergency workers quickly blocked the culverts. But local wetlands experts told InsideClimate News they're still concerned that crude from the cove will eventually pollute the rest of the lake, especially after the culverts are re-opened.
Hydrocarbons and toxic chemicals "will be leeching out into the surrounding environment over a period of years," said Ben Cash, a professor and the biology department chair at the University of Central Arkansas in Conway.
Cash is leading the state's efforts to rescue reptiles from the spill. He said that so far his team has recovered 20 snakes from the cove, out of the "hundreds or thousands" likely affected. Wildlife experts have also cleaned beavers, lizards, ducks, nutria and turtles, some of which have died. Cash didn't know how fish have been impacted.
The U.S. Environmental Protection Agency has identified the oil spill as a "major" incident. The agency has said as many as 7,000 barrels, or 294,000 gallons, have leaked out of the pipeline. Exxon estimates that 5,000 barrels, or 210,000 gallons, have spilled.
Exxon spokeswoman Kim Jordan said she didn't know how much of the oil has leaked into the cove. "We don't have breakdowns of the overall spill."
On Tuesday, a report from the joint command center said workers had removed "small, isolated amounts of oil from the cove."
Keith Stephens, a spokesman for the Arkansas Game and Fish Commission, which owns Lake Conway, said only a "small portion" of the cove has been affected. "The majority of the cove does not have oil in it," he said in an email.
The swampy cove and Lake Conway are "hydrologically different," Stephens explained. The cove is "very shallow and densely populated throughout with lily pads, causing naturally slower flow through the main cove."
The Game and Fish Commission built the lake, known officially as the Craig D. Campbell Lake Conway Reservoir, in 1948 by filling in Palarm Creek. The lake—the largest ever created by a state conservation agency—is stocked with bass, catfish and crappie, and is surrounded by two state wildlife management areas. Its creation helped boost real estate development in the nearby towns of Conway and Mayflower.
After the pipeline ruptured, local firefighters, city officials, county road crews and police officers built dikes of dirt and rock to clog the drainage pipes, Faulkner County Judge Allen Dodson told reporters.
Since then, Exxon has set up a series of seven containment booms to protect Lake Conway's main body from any oil in the cove, according to a report on Monday from the joint command center. "Tests on water samples show the main body of Lake Conway is oil-free," the report said, and pumps continue pulling water from the bottom of the cove to keep it from overflowing.
Cash, the biology professor, said state and local officials should do more to alert the public to the risks the oil spill could pose to Lake Conway's main body. Just a week after the pipeline rupture, the Game and Fish Commission gave the go-ahead for fishing and boating on the lake.
"Even if you don't have the oil that you can look at and say, 'Ah, there's the crude, black, sticky stuff,' over time you're still going to have the constituents of the crude" in the water and soil once the oil breaks down, he said.
Although Cash has been "very encouraged by Exxon's response" to the spill, he said Lake Conway could still suffer "persistent and damaging effects."
"It's disingenuous to say that [the cove] is not part of Lake Conway," Cash said. "It absolutely is connected."
The 20-inch Pegasus pipeline was carrying Wabasca Heavy crude, a type of bilbit from western Canada, when it ruptured, Exxon told InsideClimate News. When dilbit sinks in water it is much more difficult to clean up than conventional crude, which usually floats.
Wabasca Heavy contains at least 10 types of hazardous constituents, including benzene, which increases the risk of cancer. It also contains toxic chemicals like N-hexane and naphthalene, according to a Material Data Safety Sheet that the Game and Fish Commission provided to cleanup crews and was obtained by InsideClimate News.
The cleanup of a 2010 dilbit spill in Michigan's Kalamazoo River has already cost $820 million in cleanup expenses, and that figure could top $1 billion after latest operation is carried out. The Michigan spill was roughly three times the size of current projections for the Arkansas spill.