Hawaii’s only two refineries on Thursday were preparing for a pair of hurricanes approaching the archipelago, spokesmen for the companies said.

They joined Hawaiians bracing for Hurricane Iselle, which was slated to make landfall on Hawaii’s Big Island on Thursday night before passing south of the other islands on Friday.

Behind Iselle was Hurricane Julio, forecast to pass just north of the Big Island on Sunday morning, according to the National Hurricane Center.

Par Petroleum Corp and Chevron Corp each were securing their plants on the island of Oahu.

“We’re going through our checklists to make sure all is buttoned down,” said Lance Tanaka, spokesman for Par Petroleum’s 94,000 barrel-per-day (bpd) Kapolei refinery, the larger of the two plants. He said the company would later consider whether to shut it down for the storms.

Chevron said it was implementing emergency preparedness plans at its 54,000-bpd Honolulu plant in anticipation of Iselle’s wind and rain.

Both plants make gasoline, ultra-low sulfur diesel, jet fuel, marine fuel and other refined products.

Par Petroleum refinery, which supplies 31 gasoline stations on Oahu, Maui and the Big Island, said late on Thursday that the plant’s docks were shut down for the storm, which will delay resupplying those stations.

Tanaka said the company has several days’ worth of supply on the islands depending on that state of demand.

Par Petroleum last year bought the Kapolei refinery, plus storage tanks, pipelines and a mooring terminal from Tesoro Corp for $75 million plus up to $275 million in net working capital and inventory.