PORTLAND – Emergency responders planned to resume efforts this morning to keep hundreds of gallons of spilled fuel oil from contaminating sensitive ecosystems in the Fore River.

Crews on Thursday strung absorbent booms across the mouth of a cove near where the east end of the main Portland International Jetport runway approaches the river.

Much of the spilled fuel ended up in the cove and responders were working to keep it there so it could be cleaned up.

The spill was the result of an automatic pump at the new terminal failing to shut off as intended, so that it pumped as much as 600 gallons from what officials called a “day tank” up through a vent system to the terminal roof.

The oil ran into the storm drain system, which leads underground to a retention pond near the end of Yellowbird Lane adjacent to the runway and then into the Fore River, state and city officials said.

Clean Harbors Environmental Services of South Portland was cleaning what it could out of the retention pond but it appears most of the spilled oil was washing into the river cove because of the day’s rains, said Samantha Depoy-Warren, spokeswoman for the Department of Environmental Protection.

“It appears the quick response was preventing it from spreading much beyond that cove,” Depoy-Warren said. A natural eddy within the cove kept the oil from spreading, she said.

Crews suspended their efforts Thursday night after putting booms and pads in place.

The cove is inaccessible by boat at low tide and is difficult to reach by foot because it is at the base of a steep and slippery embankment, Depoy-Warren said.

Officials were first alerted to the spill by the smell of fuel shortly before noon. The Portland Fire Department responded, and when the sheen was detected on the water, they called in the Coast Guard and the Department of Environmental Protection.

By afternoon, the smell of fuel was strong around the jetport and particularly at the end of Yellowbird Lane.

The Coast Guard checked downstream in the Fore River and determined that the spill had not spread there, nor upstream into Long Creek. Later investigation showed some fuel did reach the Thompson Point Marsh. Cleanup crews from Clean Harbors are scheduled to work in the area today, Depoy-Warren said.

A biologist with the Department of Inland Fisheries and Wildlife was called in to determine whether the duck population there and in the marsh has been affected.

The Coast Guard, DEP, Portland Fire Department, jetport staff and Clean Harbors were using absorbent booms and pads to keep the fuel from spreading into Long Creek or over to Thompson Point Marsh.

A higher than normal tide started coming in at 4:40 p.m. because of the full moon. Officials said it would take at least 24 hours to ensure the spill does not spread and to clean up what can be recovered.

Barbara Parker, DEP’s director of response services, inspected the site Thursday.

Parker helped coordinate cleanup efforts in parts of the Gulf Coast following the BP spill there.

Parker described the cleanup at the Fore River as effective and said that much of the oil had been removed, Depoy-Warren said.

Staff Writer David Hench can be contacted at 791-6327 or at [email protected]