About 5,000 barrels of oil spilled from a 22-foot rupture on the Pegasus pipeline in Mayflower, Ark., in late March. Exxon said none of the oil reached an area lake, though long-term remediation efforts have focused on a neighborhood marshland.
Vice President of Exxon's pipeline division Karen Tyrone said about 3,000 barrels of oil have been recovered. Claims made by the Sierra Club that the rest is unaccounted for didn't take into account oil soaked up by special pads, oil left on trees and other residual amounts, Exxon said.
"These preliminary estimates will be revised as the investigation is finalized but the broader point is that there is no 'missing' oil," Tyrone said in a statement.
Pegasus was carrying a diluted form of Canadian crude oil at the time of the spill. That type of oil is denser than conventional crude, making cleanup difficult.
U.S. Rep. Ed Markey, D-Mass., ranking member of the House Natural Resources Committee, questioned Exxon's version of the incident response.
"The homeowners affected by this pipeline spill and the American public deserve to know what Exxon knows, when they knew it, and what they are doing to clean up this accident," he said in a letter to the company.