Roads and railroad bridges weren’t the only things that washed out in the heavy rains which hit Southcentral Alaska in September.
Marathon Oil, in the process of selling its Cook Inlet assets to Hilcorp Alaska, is dealing with a washout along Kalifonsky Beach Road near Kenai which left a segment of a gas pipeline dangling.
The Pipeline and Hazardous Materials Safety Administration, PHMSA, described the situation and action it requires in an Oct. 5 corrective action order.
The affected line is a 20-inch diameter pipeline transporting natural gas from the Kenai gas field to facilities south of Kenai. PHMSA said the line was buried parallel to and within the right of way of Kalifonsky Beach Road and crossed an unnamed stream south of Kenai near milepost 11.
The road and supporting embankment washed out Sept. 20 at the stream, exposing “a 75-foot portion of the pipeline suspended approximately 25 feet above the streambed,” PHMSA said in its order.
Approximately one mile of the pipeline between isolation valves to each side of the washout was initially shut down but is now back in service, the agency said.
PHMSA said continued operation of that segment of the line between the isolation valves “without corrective action would be hazardous to life, property, or the environment” and is requiring Marathon “to take immediate corrective action to ensure the safe operation of the pipeline.”
Gas supply
PHMSA said it had been told by Marathon that the affected pipeline transports approximately 20 percent of the supply of natural gas to Anchorage.
Marathon Oil spokeswoman Lee Warren told Petroleum News in an email that Marathon remains “committed to finding the best options for ensuring safe operations and delivering gas during this important Fall and Winter heating season.”
“Safety is our utmost concern,” she said.
Marathon is working closely with PHMSA, Warren said, “has met all of PHMSA’s deadlines and continues to comply with the corrective actions requested by PHMSA.’
She said Marathon has shared its data and independent engineering studies with the agency, and said that based on the company’s analysis and independent engineering studies of the 20-inch line, “we’re confident in the current stability and integrity of our natural gas pipelines.”
“The line is in use, and we’re confident in the current stability and integrity,” Warren said.
Gas initially rerouted
PHMSA said Marathon shut down the affected segment of line Sept. 23 and from Sept. 23 to Oct. 1, natural gas that would have been transported through the affected pipeline was rerouted through a 12-inch diameter line.
The agency said that segment of the pipeline washed out in 1967 and 1991 and there is an overhead cable system attached to the line in midair that “is believed to have been installed in 1967 following the first washout.”
PHMSA said the cables were partially buried until this year’s washout, and that the system was reported to have performed satisfactorily during the 1991 washout.
DOT work in progress
PHMSA said the Alaska Department of Transportation and Public Facilities closed the road Sept. 24 for repairs, opening a detour around the washout Oct. 1, and planned to begin road repairs as soon as possible, noting that heavy machinery and additional personnel would be in the vicinity of the affected pipeline segment during that repair work.
Rick Feller, DOT Central Region spokesman, told Petroleum News Oct. 23 that the alternate route the department established was a temporary measure.
Work for a more permanent fix of the washout area has been bid and awarded — a project called “Kalifonsky Beach Road mile post 11 emergency culvert repairs.”
The completion timeframe for the $826,000 job was originally Nov. 15, Feller said, but that may slide a week “due to coordination efforts with Marathon on that pipeline.”
He said Marathon has agreed to have their gas pipeline rerouted by Nov. 1 and the road work is expected to be completed by the third week of November.
Required corrective action
PHMSA required that Marathon verify that the affected portion of the line “can be isolated by remotely or automatically actuated emergency shut-in valves or manual valves within five minutes,” and prepare a site safety and evacuation plan.
PHMSA is also requiring “around-the-clock monitoring of the current conditions at the washout site to ensure that all activities are consistent with pipeline safety and that the geotechnical conditions have not further deteriorated.”
During road repair work, the pipeline must be depressurized, Marathon employees must be on site to monitor the road work, and once the “embankment has been raised sufficiently to allow working access to the pipeline,” the outer casing must be removed and the entire exposed pipeline inspected.
PHMSA is requiring a plan, by Jan. 31, 2013, to ensure continued safe operation and integrity of the line “and to avoid future external force damage at the water crossing, either by horizontal directional drill (HDD) or other method.” That plan must be completed by Dec. 31, 2013.
—Kristen Nelson
