Oil spills like the Deepwater Horizon and the Exxon Valdez are embedded in the environmental consciousness, so much so that they're essentially shorthand for any other spills that occur.

But there are spills that don't get as much attention — and maybe they should. For instance, the Taylor oil spill has been quietly leaking what could be tens of thousands gallons of oil into the Gulf of Mexico since 2004, six years before the Deepwater Horizon spill.

Never heard of it? You're not alone, and it could keep belching oil into the ocean for long while.

A 14-year-old oil spill

A satellite view of Hurricane Ivan on Sept. 15, 2004 A satellite view shows Hurricane Ivan on Sept. 15, 2014, about 170 miles south of the Alabama coastline. (Photo: NASA/GSFC, MODIS Rapid Response/Wikimedia Commons)

The Taylor oil spill started in 2004 following Hurricane Ivan. An oil platform, Mississippi Canyon-20, and pipeline belonging to now-defunct Taylor Energy was damaged and sank on Sept. 15, 2004, following a mudslide caused by the hurricane. The structure, according to a paper prepared by Taylor Energy officials and described in a 2013 NOLA.com article, "was subsequently located lying in an almost horizontal orientation and almost entirely buried in sediment up to 100 feet deep, approximately 900 feet from its original location and in approximately 440 feet of water."

The oil leak, located about 12 miles off the Louisiana coast and seven miles north of the Deepwater Horizon site, went relatively unnoticed by news outlets. Indeed, Taylor Energy worked hard to keep the leak out of the national spotlight, citing concerns over a loss of reputation and proprietary information about its business practices, according to a legal settlement from 2015. If it hadn't been for the Deepwater Horizon spill, the Taylor spill might have gone unnoticed for even longer.

A shadow of another slick

In 2010, during the Deepwater Horizon spill, local activists performed flyovers of the area to monitor the extent of that spill. In the process, however, they noticed a shadow of another slick that didn't match the main spill.

"They said it couldn't have been coming from the BP spill, and sure enough, it wasn't," Marylee Orr, the executive director of the Louisiana Environmental Action Network (LEAN), told CNN. "It was coming from the Taylor Well."

It took time, however, for organizations like LEAN, Apalachicola Riverkeeper and other Louisiana environmental groups to get answers. In 2012, LEAN and the others sued Taylor Energy, beginning a three-year litigation process that culminated in the aforementioned 2015 settlement. In addition to detailing the state of the platform, Taylor Energy claimed that the sheen near the site was "residual" and that "there is no evidence to suggest" the presence of an ongoing leak.

Just how much oil has been leaked?

Since disclosing the leak to the National Response Center, Taylor maintained the stance that the leak was minor. Surveys conducts by organizations like SkyTruth and investigations by the Associated Press countered these claims, and in 2015, the U.S. Coast Guard released a leak estimate that, according to Greenpeace, was about 20 times larger than what Taylor Energy has reported in court filings.

The scope of the Taylor spill has proven difficult to quantify. SkyTruth, using data given to the Coast Guard by Taylor Energy, estimates that from 2004 to 2017, between 855,421 and 3,991,963 gallons of oil have leaked into the Gulf. John Amos, founder of SkyTruth, told CNN that this estimate was almost certainly too low as it relied on data supplied by Taylor Energy.

The Deepwater Horizon spill resulted in an estimated 176.4 million gallons (4.2 million barrels) of oil, according to CNN.

A boat sails through an oil slick caused by the Deepwater Horizon oil spill A boat sails through an oil slick caused by the Deepwater Horizon spill. If not for that spill, the Taylor spill may not have been brought to public attention. (Photo: kris krüg/Wikimedia Commons)

A Department of Justice report, released in mid-September, relied on satellite data instead of Taylor Energy-supplied numbers. This report suggests that about 250 to 700 barrels a day (that's roughly 3.8 million gallons to 10 million gallons a year), are leaking into the ocean.

The DOJ report comes at a critical time for both the federal government, represented by the Department of the Interior, and Taylor Energy. The entities have been involved in a protracted legal battle as Taylor Energy seeks to recover more than $400 million left from a $666 million trust fund established in 2008 that was to be used to clean up the Mississippi Canyon-20. The energy company claims there is no active leak, and the oil that surveys have found is escaping naturally from the seafloor. The DOJ and DOI both maintain that Taylor Energy has not done its duty in plugging the site.

According to The Washington Post, Taylor Energy and its contractors were asked to locate the the wells under the mudslide and cap them. If that was not possible, a device needed to be created to contain the leak. Taylor Energy was not allowed to drill or bore through the mudslide, however, due to concerns about exacerbating the spill. The company has plugged about a third of the 21 wells and erected a shield of some kind that was supposed to prevent the oil from leaking.

Taylor Energy, which sold all its oil and gas assets to Korea National Oil Corporation and Samsung C&T Corporation in 2008, maintains a single employee — company President William Pecue. Pecue has maintained that the leak is an "act of God under the legal definition."

Why is a spill that started in 2004 still leaking oil in the Gulf of Mexico?
An oil platform and pipeline belonging to now-defunct Taylor Energy was damaged by a hurricane and sank on Sept. 15, 2004. That spill is still leaking oil.