Oil has been washing up on Orange County beaches since a leak in an underwater pipeline from an offshore platform sent tens of thousands of gallons of heavy crude into the ocean waters. The spill fouled the famed sands of Huntington Beach, and could keep the ocean and shoreline closed there and in some other communities to the south for weeks.

Here’s a look at what happened, who’s involved and the aftermath:

What happened?

Boaters off Orange County and residents of Newport Beach started reporting a petroleum smell in the air and oily sheen on the water Friday afternoon, Oct. 1.

The following morning the Coast Guard confirmed a spill. The sheen on the ocean was miles wide and crude started washing ashore in sticky, black blobs. The leak occurred about 5 miles offshore at a depth of about 98 feet and came from a pipeline owned by Amplify Energy. The Houston-based company also owns and operates three nearby offshore platforms that pipe oil into Long Beach.

Oil first washed up in Huntington Beach, including Talbert Marsh, a sensitive wetland. Crude was later spotted down the Orange County coast, in Newport Beach, Laguna Beach and Dana Point. By Thursday tar balls were reported washing up in Carlsbad, in San Diego County.

How much oil leaked?

It’s still a mystery.

Amplify Energy publicly said no more than 126,000 gallons flowed from its pipe. But the company also told federal investigators the total may be 29,400 gallons. On Thursday, the Coast Guard announced its own estimate of at least about 25,000 gallons and no more than 132,000 gallons.

David Pettit, a senior attorney at the environmental group Natural Resources Defense Council, finds it hard to believe Amplify doesn’t know how much oil it lost. “If they know what the flow rate was in the pipeline, and how much the pressure dropped, and for how long, you could calculate that in a matter of minutes,” Pettit said.

How was the leak discovered?

A commercial vessel anchored off Huntington Beach reported to a national hazardous spill hotline staffed by the Coast Guard that it saw a sheen more than 2 miles long just after 6 p.m. Friday night.

A satellite image shot by the European Space Agency indicated a likely oil slick in the area around 7 p.m., which was reported to the Coast Guard at 2:06 a.m. Saturday after being reviewed by a National Oceanic and Atmospheric Administration analyst.

The Coast Guard said it did not act on either report, deciding to wait until daybreak because darkness and a lack of technology would hamper its search for oil.

Amplify CEO Martin Willsher said the company did not discover the leak until it saw oil in the water at 8:09 a.m. Saturday.

However, other reports indicate the company had signs of a leak as early at 2:30 a.m. Saturday. Federal regulators said an alarm on Platform Elly alerted a control room operator at that time to a drop in pipeline pressure that could indicate a leak.

The company did not report the leak until 8:55 a.m., according to the California Office of Emergency Services. The company that reported the leak on behalf of Amplify said the incident occurred at 2:30 a.m.

Around the time the company reported the spill, the Coast Guard said it located oil in the water.

Will the oil reach Long Beach?

At this point, nearly a week after the spill first occurred, there are no reports of oil or tar balls washing up on Long Beach’s seven miles or so of beaches. At this time, prevailing air and ocean currents continue to push the oil spill south, toward Orange and now San Diego counties.

Should that change, city officials are prepared to clear the beaches and begin mitigation efforts, they announced on Oct. 3.

Could this have happened in Long Beach?

Yes. Different currents at the time of the rupture could have resulted in oil impacting the Long Beach or San Pedro coastline.

There are 27 oil and gas platforms, six artificial islands and about 200 miles of oil pipelines off the coast of Southern California, according to the Bureau of Ocean Energy Management, a federal agency that regulates offshore energy production. While not all of that infrastructure may impact Long Beach in the event of a leak or rupture, there are numerous facilities and pipelines—some of which lie within the city’s breakwater—that lie directly offshore.

And much of that equipment is old. The San Pedro Bay Pipeline that ruptured was built in 1980, as were the platforms that it connects to the Port of Long Beach. Though the Environmental Impact Report for the platforms and pipeline estimated a 35-year lifespan, there are no current decommissioning plans.

“We have over 60,000 miles of oil pipeline in the U.S.,” said Aquarium of the Pacific President and CEO Peter Kareiva. “Half of that 60,000 miles is over 50 years old. Oil pipelines start failing at age 40.”

The infrastructure closer to Long Beach is even older, according to Kevin Tougas, manager of the city’s oil operations bureau. The THUMS islands—the four artificial islands named for astronauts killed in the line of duty—date to 1965, as do seven of the nine pipelines that service them, according to Tougas (two pipelines were laid down in 1988 and 1992).

That said, the THUMS islands were designed to act like bowls in the even of spills, preventing any oil from reaching the ocean, Tougas said. The city also requires a variety of pipeline inspections in excess of those mandated by federal regulators, he added.

“We view these things as our lifelines,” Tougas said. “Any leak in the ocean is a non-starter.”

Who’s responsible for the Orange County spill?

The cause is under investigation.

Amplify CEO Martin Willsher first suggested Monday that an anchor from one of the many commercial vessels that use the massive Los Angeles-Long Beach port complex might be to blame. The next day the Coast Guard said divers found that a 4,000-foot section of the pipeline was “laterally displaced” by about 105 feet. It’s bent “like a bow string,” Willsher said.

Video of the ruptured pipeline released by the Coast Guard showed a thin 13-inch-long crack that experts said could indicate a slow leak that initially was difficult to detect.

Federal transportation investigators said preliminary reports suggest the failure may have been “caused by an anchor that hooked the pipeline, causing a partial tear.”

On Wednesday, Coast Guard investigators boarded the Rotterdam Express, a massive German-flagged container ship that was assigned an anchorage closest to where the pipeline ruptured.

Hapag-Lloyd, the shipping company that operates the vessel, said the Coast Guard interviewed the captain and crew and was provided access to the logbook showing the ship’s locations. Afterward, the Coast Guard called the company to say the Rotterdam no longer was under scrutiny for the spill, the company said. The Coast Guard did not comment.

What’s the environmental impact?

That will depend on how much oil is out there.

Local officials, who feared an environmental catastrophe at first, have more recently voiced hope that the total spill will be less than initially feared. So far, only a handful of oiled birds have been recovered. Teams are out searching for affected animals in the spill area and beyond. Environmentalists say it’s too soon to know how many seabirds, marine mammals and other animals will ultimately be affected by the oily film covering marsh areas and floating on the ocean—or for how long.

Researchers say the impact on animals will take a while to understand. They are just starting to learn about some of the long-term effects from the 2010 Deepwater Horizon oil spill. And many problems remain unseen as oil components build beneath the surface of the ocean.

Out on the water by the rigs, there’s no visible sheen and no stench of oil like the putrid odor that pervaded Huntington Beach in the days after the incident.

Staff Writer Anthony Pignataro contributed to this report.

No firm tally of how much oil leaked from pipeline