A Louisiana company wants to retire a segment of a 59-year-old natural-gas pipeline that runs about 200 feet from the site where Exxon Mobil’s Pegasus crude-oil pipeline ruptured in Mayflower last spring.
But Enable Gas Transmission LLC of Shreveport wants to build a new line that will cross the Pegasus nearby.
A pipeline-safety consultant said Monday that co-location - called “collocation” in the industry - of such lines is common and does not trouble him.
Operators, however,should be aware of other nearby lines and take appropriate safety precautions, said Richard Kuprewicz, who is advising Central Arkansas Water on matters relating tothe Pegasus, which crosses the Lake Maumelle watershed. Kuprewicz said he did not know of any pipeline explosions that had led to the explosion of any nearby, second line.
Another safety expert, Carl Weimer, said in an email Monday: “From the safety side it is often wondered if it is smart because people fear that if one pipeline should explode it would cause the others to explode too. This makes sense, but I [cannot] think of a single instance where this actually occurred.”
Enable Gas Transmission has begun seeking federal, state and local agencies’ approval to take the required actions that would allow it to change part of its pipeline system’s route in Faulkner and Pulaski counties and to re-purpose other lines in the area.
The proposed changes have “nothing whatsoever to do with the Pegasus pipeline,” said ErikDilts, director of environmental projects for parent Enable Midstream Partners.
Federal documents indicate that the site where the Pegasus line ruptured in Mayflower’s Northwoods subdivision is about 200 feet west of the current gas line, which would be retired. But Dilts said the plan calls for a new line that would replace it to cross the Pegasus “approximately a half-mile to the west of that specific location.”
Enable’s line near Maumelle does not go through the Lake Maumelle watershed now. Nor would it under the proposed changes, said Central Arkansas Water spokesman John Tynan.
Under the proposal, a natural-gas transmission line running through the University of Central Arkansas campus in Conway and through the Conway Municipal Airport will be switched to a distribution line and ownership will be transferred from Enable Gas to CenterPoint Energy Resources Corp., an official of Enable Gas’ parent company said. CenterPoint, Enable’s affiliate distribution company, does business as CenterPoint Energy Arkansas Gas.
Gas travels through distribution lines at a lower pressure than through transmission lines, Dilts said.
Enable first began trying to make changes in its central Arkansas system about two years ago, said John Reisz, a senior environmental specialist for the company. Enable originally proposed another route but had to revise the plan because of right-of-way issues, he said.
Enable’s revised proposal is before the Federal Energy Regulatory Commission, not the federal Pipeline and Hazardous Materials Safety Administration.
Neither the commission nor the safety administration has taken a position on whether pipelines should be co-located, said safety administration spokesman Damon Hill and commission spokesman Mary O’Driscoll.
But Hill said companies often take the co-located approach to avoid additional zoning issues.
Weimer, executive director of the Pipeline Safety Trust, agreed, saying, “It is a very common practice to have multiple pipelines in a single right of way. I have seen up to [eight] in one corridor.
“The federal government … was looking at this a few years ago as a way to minimize environmental impacts by co-locating pipelines and other utilities so as to not disrupt habitat, wetlands, forest cover, etc. as much as with multiple rights of way all cutting distinct paths through an area,” Weimer added.
“There seems to be some value in this practice, since it would also minimize the amount of land that pipeline companies would need to take from property owners, and also saves the pipeline company some money in easement acquisition,” he said.
If pipelines are far enough from each other in a right of way, Weimer said, the distance should prevent a potential explosion.
Hill said companies are required to allow a “certain amount of distance” between pipelines and any other underground structure,” including telecommunications equipment, he said. Preventing pipelines from touching each other also helps prevent corrosion, he noted.
Weimer said that when one pipeline fails in a right of way, others in that area “may be shut down for a time to assess whether any damage was done to them.”
Still, he added, “I can’t think of an incident where one failed pipeline caused another to fail also. I think the potential for this to occur is real, especially where [pipelines] cross each other, but has not been a problem that we have seen - yet.”
When the Pegasus line ruptured March 29 in Mayflower, Enable “put a monitoring plan in place per our normal procedure primarily focused on excavation and other [third] party activities associated with spill follow up,” Enable spokesman Alicia Dixon said in an email. “We did not shut down the pipeline.”
Exxon Mobil has estimated the Pegasus line spilled 210,000 gallons of heavy crude oil into the residential neighborhood, ditches and a cove of Lake Conway.
“It’s probably a good idea to keep [nearby lines] flowing; it takes away the heat,” Kuprewicz, the consultant to Central Arkansas Water, said.
Kuprewicz believes that most operators are aware of neighboring lines. That’s good because rights of way are rarely but sometimes “so constrained that [companies] had to put pipelines under multiple depths” and the lines become “stacked like airplanes,” he said.
In an October filing with the Federal Energy Regulatory Commission, Enable said co-location “would minimize environmental impacts.”
But the company also said that “siting a natural gas pipeline directly within existing pipeline and directly within existing pipeline and electric transmission line rights-of-way could pose constructability, safety and operational concerns. For these reasons, [Enable] proposes to abut,rather than overlap, the existing electric transmission line right-of-way, thereby balancing the need to minimize environmental impacts with the need to provide for safe and efficient pipeline construction and operation.”
That report more than once broached the Pegasus pipeline rupture in addressing environmental issues that might arise during work on the proposed project.
“If a hazardous waste site is encountered during construction of the Project or retirement activities along Line B, [Enable] would stop work activities in the immediate vicinity of the site” and notify federal agencies, the company said.
Enable said in an application notice published last week that it expects construction of the proposed replacement pipeline to begin in March, subject to government approvals and permits.
That notice said the proposed project will provide for “the continued safe, reliable and efficient transportation of natural gas to the central Arkansas cities and towns of Conway, Mayflower, Maumelle, North Little Rock, and Little Rock.”
This region “has experienced substantial residential and commercial development since the original pipeline facilities were constructed,” the notice added. “The Project provides [Enable] with the opportunity to install new facilities to better service its current customers , while also laying the groundwork for additional capacity to meet future growth, as needed.”
Exxon Mobil Corp. spokesman Aaron Stryk said Monday that Exxon has no position on the Enable proposals.
O’Driscoll said the comment period on Enable’s application before the federal commission ends Thursday. But she said any scheduling notice that could be filed would open a 90-day window on environmental issues.
Front Section, Pages 1 on 12/31/2013