A crude oil spill from an undetermined source at the Swanson River oil field in the Kenai National Wildlife Refuge was discovered by a power pole survey crew the afternoon of July 20.
Chevron, the field operator, reported the spill to the Alaska Department of Environmental Conservation later that day and has estimated the volume at 630 gallons.
DEC said the spill occurred above a buried pipeline corridor containing both active and inactive piping along a roadway near pad 21-27 at the field.
The agency said July 21 that the active 6-inch oil line was isolated by valves and the two wells serviced by the line have been shut down.
The pipeline corridor will be excavated to determine the source of discharge.
DEC said Chevron personnel deployed sorbent boom and pads on both sides of a culvert under the entrance to pad 21-27 and along a natural drainage area down gradient of the spill site. Boom was also placed in a standing water body some 700 feet from the spill location.
There are dense grasses, surface and standing water along the pipeline corridor, DEC said. The dense grasses along the roadway will be cut to expose more of the ground surface for better delineation of the impacted area and the pipeline corridor will be excavated to determine the source of the discharge.