In May, a 24-inch pipeline break near California’s Refugio State Beach, 20 miles west of Santa Barbara, released more than 100,000 gallons of crude oil into coastal areas and the Pacific Ocean, threatening four marine protected areas.

Gov. Jerry Brown moved quickly and declared a state of emergency to free up resources for the cleanup. Experts and trained volunteers began the task of rescuing oil-soaked animals — from shorebirds to seals — that began turning up on the beaches. SeaWorld San Diego suspended shows so its employees could assist with the cleanup efforts, and volunteers with Santa Barbara County Community Emergency Response Team and California Conservation Corps assisted in clearing oil and rescuing animals.

However, at least one expert cautioned that it’s nearly impossible to mop up an oil spill completely.

“The consequences of what you can’t see are as important as what you can see. You can’t ever get it all out,” said Phyllis Grifman, associate director of the USC Sea Grant Program, in an interview with the Guardian. “There are so many nooks and crannies where the oil can hide.”