Federal agencies have so far not decided whether to undertake an assessment of the ecological harm caused by ExxonMobil's pipeline break, which spewed a tarry oil slick into yards, streets and creeks in a central Arkansas town.
For now, they're leaving it to state agencies to decide whether and how to quantify and counteract the environmental damage.
The rupture in the Pegasus pipeline on March 29 dumped up to an estimated 294,000 gallons of Canadian heavy crude in Mayflower, Ark.—including in a cove that flows into Lake Conway, a major fishing lake. If that estimate turns out to be correct, the Arkansas spill would be one-third the size of a 2010 Michigan pipeline spill, the worst accident of its kind in U.S. history.
Experts say that after oil spills, hydrocarbons and toxins leech into the soil and sediment and travel up the food chain as fish and animals eat contaminated species. The oil can also kill crucial erosion-protecting vegetation.
It can take years and millions of dollars to restore the environment.
"Ecosystems provide the most basic forms of sustenance for us: our food supply, our drinking water, protection against floods and natural disasters," said John Kostyack, vice president for wildlife conservation at the National Wildlife Federation. "When you start breaking down those ecosystems, you start losing that."
The Arkansas Department of Environmental Quality and the Arkansas Game and Fish Commission are in charge of surveying the damage to oil-hit wildlife, wetlands, soil and groundwater along the mile-long spill site.
The two agencies told InsideClimate News they have little experience in handling a major oil spill like the one in Mayflower.
When major oil or chemical accidents hit, federal and state agencies have the option to do a damage assessment together through a legal process called the Natural Resource Damage Assessment and Restoration Program, or NRDA (pronounced nerd-ah). Through a NRDA, agencies determine the cost of ecological destruction from spills and develop a plan to restore the ecosystem that must be paid for by the responsible parties. States cannot do a NRDA on their own.
Federal agencies that can conduct a NRDA are the National Oceanic and Atmospheric Administration (NOAA), the five Interior department bureaus—including the Fish and Wildlife Service—plus the U.S. Departments of Agriculture, Energy and Defense, as well as federal Indian tribes.
NOAA, which manages marine ecosystems, said it has no plans to take a NRDA approach in Mayflower. "We don't think [the oil] is impacting NOAA trust resources," said spokeswoman Keeley Belva.
The Fish and Wildlife Service, the only federal agency directly involved in the Mayflower spill that does NRDA work, said it hasn't made a decision yet.
"The state's got the lead," said Jim Boggs, a field supervisor at the service's Arkansas office.
What the State Is Doing
The state Game and Fish Commission plans to hire a private consultant in the next few weeks to quantity the damage to wildlife and Lake Conway and create a plan to restore the ecosystem. The work to restore the environment is expected to be paid for by Exxon, according to commission spokesman Keith Stephens. He said neither Exxon nor federal agencies would have a say in the decision on the consultant.
The Department of Environmental Quality will do its own damage assessment. Ryan Benefield, the agency's deputy director, said about 10 engineers, geologists and water scientists will soon begin "extensive sampling" of sediment, soil, groundwater and surface water in areas where much of the oil has been cleaned up.
Time is not on their side, however.
Collecting data on oil-damaged areas is critical in the first days after a spill because the oil is still visible, said Jeffrey Short, a scientist at Oceana, a conservation organization.
"You lose information at an exponential rate after an incident occurs" as oil settles and is absorbed in the surrounding ecosystem, said Short, who worked for 31 years as a NOAA research chemist. For much of that time he was involved in damage assessment for the Exxon Valdez oil spill.
Not long after the oil spills, "there's a blackout period where things are happening in the environment and you can't see them," he said.
The Challenge of Dilbit
Short said the problem is especially worrisome for diluted bitumen, or dilbit, the type of oil that spilled from Exxon's pipeline in Arkansas. The heavy bitumen crude is diluted with chemicals and light hydrocarbons so that it's thin enough to flow through pipelines. When it hits the water, and the diluents evaporate, the bitumen sinks to the bottom and accumulates in the sediment.
"Once it sinks, how do you tell where it went ... unless you have a means of evaluating it in the field?" Short said.