Small oil spill at Valdez pipeline terminal under investigation

A crude oil spill at the Valdez Marine Terminal was under investigation after workers reported a sheen on the water Thursday morning.

The source of the spill at the terminal's western end was secured by crews Thursday, terminal operator Alyeska Pipeline Service Co. said in a statement.

Alyeska estimates the spill at between 10 and 50 gallons of crude oil residue, the Alaska Department of Environmental Conservation said Thursday evening.

"Teams on scene have boomed the area where sheen was visible and are carrying out spill response and recovery tactics, including skimming," Alyeska said.

No oil tankers were docked at the berths near the area where the spill occurred, the company said.

A variety of spill cleanup boats and skimmers were responding, and no wildlife impacts were reported, the agency said.

Oily residue on the water was reported shortly after 11 a.m. Thursday, near a fire water pump intake, the state agency said.

"The cause is under investigation, but early indicators show a check valve in the fire water system may have failed during a pressure test, allowing contents of a berth loading arm to drain through the fire water system," the agency said.

Alyeska said it's cooperating with state and federal officials.