Editor’s note: This story has been changed to correct an inaccurate use of the term “secondary confinement.” The correct term is “secondary containment.”

While so far few damages have been reported from Tuesday’s 7.9 magnitude quake, a Nikiski refinery reported a small oil spill at one of its outdoor tanks.

In Nikiski, tremors from the earthquake sloshed between five to 10 barrels of crude oil — 420 gallons at the maximum estimate — over the top of an outdoor tank at Andeavor’s Kenai Refinery. The oil was contained around the tank and didn’t permeate into the ground, according to Andeavor spokesperson Kate Blair.

“Crude spilled out of the vents at the top, but it spilled into secondary containment,” Blair said. “I like to describe it as filling up a rain barrel in a bathtub. The tank sloshed around, but everything stayed inside the bathtub.”

The containment area is bordered by an earth berm and floored with an impermeable cement-like material. Most of the spill didn’t reach the ground, according to Alaska Department of Environmental Conservation Program Specialist Jade Gamble, a local responder who was one of two DEC personnel at the site Tuesday morning.

“Most of the oil is stuck to the outside of the tank — it ran down the side of the tank,” Gamble said. “There wasn’t a lot of standing oil on the ground — little tiny puddles, and they were able to vacuum up a few gallons, but most of it is across the side of the tank.”

Blair said Andeavor (known as the Tesoro Corporation before changing its name in August 2017) had followed its emergency plans in reaction to the earthquake, setting up an operations center at its headquarters in San Antonio, Texas. A tanker vessel docking at the refinery’s terminal pulled away during the earthquake and the terminal and pipeline operations went “into essentially shutdown,” Blair said.

“With the spill, we had some refinery stoppages, but everything is back up and running as normal,” Blair said Tuesday morning.

The tank had also spilled some oil during the 7.1 magnitude Iniskin Earthquake that rattled the peninsula on Jan. 24, 2016, Gamble said. Since then, she added, Andeavor had dropped the level in the tank about 6 inches in an attempt to prevent spilling in future earthquakes. Now, she said, the refinery has been considering adding a floating lid inside the tank.

The tank spill was the only earthquake-related incident that DEC had been informed of by Tuesday afternoon.

Other local oil and gas businesses also reported no damage. Lindsay Hobson, spokesperson for natural gas distributor ENSTAR, said the company hadn’t found any gas leaks in its pipeline system following the earthquake. After the 2016 Iniskin Earthquake, gas from a breached ENSTAR pipeline caused an explosion and fire in Kenai’s Lilac Lane neighborhood.

Hilcorp spokesperson Lori Nelson wrote in an email that although the earthquake caused no damage or injuries to her company’s facilities or workers, Hilcorp had shut down and inspected two of its pipelines. One, running from the Swanson River field, had been returned to service by Tuesday evening. As of press time Tuesday night the other, the Cook Inlet Pipeline, was still under inspection.