The collapse just before noon Friday left a line of large pipes and support structures toppled outside a building.
Officials say heavy rains and an ongoing $13 million construction project at the plant also contributed to the spill.
They say the woman was pronounced dead at the scene Monday afternoon.
Takuma Sato of Japan won the 101st running of the Indianapolis 500.
Utility crews were working to repair a power outage in the area about 15 miles south of Terre Haute when Ray Lockhart was shocked.
More passengers involved in December's Megabus crash on I-65 are filing lawsuits.
Megabuses were involved in three crashes in Indiana over the past few months, and another bus was taken out of service Wednesday because of safety concerns.
A stolen car crashed into a Greyhound bus on Sunday, killing the car's driver and injuring 18 bus passengers.
A 9-year-old girl and 6-year-old boy were hit by a school bus this morning. Both have been hospitalized.
Officials have been trying to clean up a fuel tanker accident after it overturned Sunday night.