Previous inspections showed movement, erosion at site of Marathon oil spill, report says
In a preliminary summary released Tuesday, the National Transportation Safety Board reported previous in-line inspections performed for Marathon Pipe Line reportedly identified pipeline movement, erosion and the soil caving in the area near a March pipeline rupture.
The report stems from an ongoing investigation into an estimated 3,900 barrels of oil spilled in Edwardsville March 11 from Marathon’s Woodpat pipeline. There were no human fatalities, though 26 animals died.
The Woodpat pipeline was constructed in 1949 and purchased by Marathon in 1968. Previous inspections had been performed by contractors hired by the oil company, and the pipeline was last hydro-statistically tested in 2018, the report states.
Investigations are still ongoing, but here’s what has been released thus far:
The report said preliminary information indicates shortly after the rupture, Marathon pipeline staff were alerted to a rapid drop in pipeline pressure by a rate-of-change alarm from a supervisory control and data acquisition system. The control center remotely closed valves at the two nearest pump stations, isolating the pipeline.
The pipeline pressure was about 479 pounds per square inch, gauge, immediately before the rupture. The maximum operating pressure is 881 pounds per square inch, gauge. Pounds per square inch “gauge” means atmospheric pressure is not factored in the measurement.
Routine batch movement of heavy, sour crude oil was progressing as expected before the incident.
Investigators found a “complete circumferential separation” at the spot of a weld where the oil was leaking. The ruptured weld and an adjacent girth weld were taken by the NTSB for evidence and laboratory testing, the report stated.
The leaked crude oil affected about 7 miles of Cahokia Creek, and the farthest location where oil was recovered was about 2.5 miles from the Mississippi River.
Marathon sent out its oil spill response contractors, who deployed contamination booms, vacuum trucks and staff at 10 locations. The report said cleanup and remediation efforts are still ongoing, one month after the incident.
About 10,000 cubic yards of oily soil had been removed for disposal as of April 5, according to a Marathon press release. The boom is on the channel at Old Alton Edwardsville Road bridge, and it will remain there until the cleanup process is complete. The public is asked to continue avoiding the recovery zone.
The investigation by NTSB is ongoing as well, and its report said future investigative activity will focus on geohazard management, metal science and comparing the forces exerted on the pipeline to its ability to withstand strain and ongoing environmental response.
The NTSB is a federal agency that investigates civil transport incidents.
Effects on wildlife
As of April 5, Marathon reported 41 animals had been affected by the spill. Twenty-six animals have died, including 15 ducks, three herons, one hawk, one turtle, one frog, three beavers, one raccoon and one muskrat. Four ducks, a barred owl, three snakes, four turtles and one frog have been recovered and returned to the wild.
One mallard and three beavers continue to be treated at a nearby wildlife rehabilitation center. The spill area is still being monitored 24 hours per day for affected wildlife.
Ten animal fatalities and 14 “impacted” animals were reported in Marathon’s first comment on animal fatalities resulting from the spill, March 15.
In a March 24 update, Marathon officials said 40 total animals had been affected. This report also said most wildlife had been found early in the cleanup process and there had been a steady decrease in wildlife impacts as cleanup had progressed. Two animal deaths were reported between the March 24 and most recent update.
This story may be updated.
This story was originally published April 12, 2022 at 6:14 PM.
