The oil spill that closed Orange County beaches earlier this month was likely around 25,000 gallons, the lower end of early estimates, U.S. Coast Guard officials said Thursday.

This is a much less damaging scenario than previous worst-case estimates of 131,000 gallons or more. Besides the fact that there is no longer a large plume of oil floating offshore, this suggests that the county’s coastline has suffered the worst damage the spill could inflict.

While there is no final decision on how much oil was spilled, U.S. Coast Guard Lt. Rebecca Ore said officials expect it to be much closer to the lower end of the range. that they reported earlier.

“We have a high degree of confidence that the amount of the spill is around 588 barrels,” Ore said. This equates to approximately 24,696 gallons.

The spill occurred around Oct. 1, according to appeals and other reports to regulators, and it came from a damaged pipeline connected to an oil rig off the coast of Huntington Beach. Several separate investigations to determine exactly when and how the spill occurred and who should be held responsible are underway, but can take months or years.

Where did the oil go?

Early reports indicated the oil slick could be up to 13 miles long, and satellite and aircraft images collected by the National Oceanic and Atmospheric Administration showed a large slick of oil floating off the county’s coast. Orange for over a week. So what happened to him?

Evaporation, wind and wave shaking, and other processes – scientists call it “natural attenuation” – have combined to change the consistency of the floating oil slick and break it up.

“Initially, a lot of the volume goes away because it evaporates,” said Matthew Bracken, professor of ecology at UC Irvine. Evaporating components of crude oil, called volatile organic compounds, are what you smell when you pour a drop or two at the gas station.

“Twenty percent of the volume can go off pretty quickly,” he said, “but what’s left, it gets more and more viscous and that’s where the tarballs come from.”

After evaporation, which occurs in the first hours or days after a spill, the viscous pool of residual oil floats to the ocean surface, where it is agitated by the tides – and Monday through Tuesday, Strong winds also helped shatter it, said Roy Kim, an environmental specialist in the state’s fish and wildlife spill prevention and response office.

Tar balls are still washing up in Orange and San Diego counties, and cleaners continue to comb the sand for them, as they did Thursday morning at Crystal Cove State Park. Some knelt on the sand and sifted it with gloved hands, and others used rakes to search for the sticky tufts as the waves crashed and a few dolphins swam behind them.

Kim said the most recently spotted tar balls are much smaller than in the days immediately following the spill. But officials said while the plume dispersed – nothing was spotted on flights along the coast up to 2-3 nautical miles for at least four days, said Amy Stork, carrier. say the multi-agency group leading the clean-up effort – this doesn’t mean there is no more oil in the environment.

The tar balls are still coming

Although about 5,500 gallons of oil and more than 13 barrels of tarballs were picked up by boats early on, and more than 450,000 pounds of sand and oily debris were collected for disposal, experts say it’s almost impossible to get everything.

On the plus side, “as the oil ages it becomes less toxic to us and to wildlife,” said Fish and Wildlife Lt. Christian Corbo, the state’s on-site spill response coordinator. . In the end, it becomes like “a block of asphalt”.

But it’s hard to say how long the tarballs from the spill will continue to wash off, cleanup officials said. They also pointed out that due to the natural seepage of oil, it is not uncommon to sometimes find tar spots on the beach.

The clean-up effort includes laboratory analysis of a portion of the tarballs to determine if the oil is coming from that particular spill.

Since the spill, a team of more than 1,000 state and federal clean-up experts have converged in Orange County, but for some of them the job is likely to come to an end.

With the reopening of the city of Laguna Beach coastline and waters operated by South Laguna County on Thursday, the last remaining stretches of coastline after the spill are once again open to the public. Several local agencies have tested the water quality and found it safe for short-term exposure. Fishing and shellfish capture near the shore is still prohibited.

Coast Guard Ore said over the next two days officials could start scouring the coastline to make recommendations on closing clean-up efforts along specific sections of the beach.

So far, officials have not released estimates on the cost of cleaning up the spill, but said they would seek to recoup those costs from the operator of the leaked pipeline.

long term worries

Some environmentalists are concerned about the long-term effects of persistent tar deposits that may have leaked into the water or stuck to rocks and plants in the marine environment.

Bracken of UC Irvine said polycyclic aromatic hydrocarbons – what is left over from oil after evaporation – is particularly toxic to the smallest animals and plants in the ocean.

“Big animals have very good ways of getting rid of toxins, but little ones, they can’t handle them, so it makes them grow slower and kills them prematurely,” he said.

Pete Stauffer, environmental director of the nonprofit Surfrider Foundation, said we don’t know the full impact of leftover oil on marine habitat.

“I think this is why not only the ongoing cleanup, but the ongoing assessment work in environmental litigation that will take place in the months and years to come will be so important,” he said. “Just because something is not visible does not mean that it is not yet present in some form or another. “

Editor-in-chief Laylan Connelly contributed to this report.