A sheen of light oil or gas bubbled up from the floor of Cook Inlet Monday near Unocal's Dolly Varden oil and gas production platform, but it appeared to have disappeared by Tuesday.
Spotted just after 1 p.m. on Monday, the sheen was about 2 miles long and a half-mile wide, with about 25 percent of that area covered. The Alaska Department of Environmental Conservation said the oil was barely visible and then only during slack tide. The type and the amount of the substance, either a light oil or a natural gas condensate, is not known for sure.
It appears, however, to have come from a tiny leak in an 8-inch natural gas pipeline that runs from the Trading Bay Production Facility on the western shore back to the platform, where the gas is used to produce power.
A helicopter survey Monday evening with the Coast Guard and DEC before the sun went down did not find recoverable quantities of the substance.
Leslie Pearson, the state on-scene spill coordinator for DEC in Anchorage, said no more bubbles or sheen were seen Tuesday morning. She added that the substance was so light, it has probably already dispersed or evaporated on its own.
Roxanne Sinz, public affairs manager for Unocal in Anchorage, said there was no pressure drop in the 33-year old pipe, indicating it must be a very small leak.
"We made arrangements to go out in a boat and take samples (Tuesday), but there was nothing showing," Sinz said. "As a precautionary measure, we stopped the gas flow and filled the pipeline with filtered Cook Inlet water to conduct a hydrostatic test."
She said the results of the pressure test were due late Tuesday evening. She said a "pig," a device used to clean the pipeline, was sent through the line Tuesday. Stopping the flow of fuel to the platform did not disrupt operations.
Sinz pointed out there are several methods in place to detect and prevent leaks, as well as procedures on how to respond in the event of one.
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