Rim Country’s roughly 170 miles of underground propane pipeline differs in several important ways from the natural gas line that exploded in California, killing four people and blowing up 37 homes, said Semstream Arizona Propane General Manager Douglas Mann on Monday.
Payson’s relatively low-pressure, plastic propane pipeline doesn’t resemble the high-pressure steel pipe that flared up near San Francisco, said Mann.
While the California pipeline’s diameter measured 30 inches, Rim Country’s largest line measures 6 inches. The smaller pipeline carries less pressure. Mann said large lines could carry roughly 800 pounds per square inch of pressure, while Payson’s carries at most 30 pounds per square inch.
“That’s quite a difference,” said Mann.
Payson’s underground system was installed in 1968 as one of the first plastic piping endeavors. Now, most communities have plastic pipe for delivery, said Mann.
In California, Mann said investigators believe a rupture in the steel pipeline’s welding may have contributed to the blast. “Payson has no steel underground, so things like rust and corrosion are not an issue,” he said.
However, if a company wants to transmit large quantities of highly pressurized gas, it must construct the pipe of steel because of the pressure.
Meanwhile, policy makers nationwide have felt the blast’s effects. The federal Department of Transportation has proposed new legislation increasing oversight.
U.S. Secretary of Transportation Ray La Hood sent to Congress legislation that would more than double the maximum fine for serious violations from $1 million to $2.5 million.
LaHood also wants to hire 40 more inspectors and other enforcement personnel over the next four years, according to DOT.
In Arizona, the Corporation Commission will require SemStream next month to outline its pipeline inspection process in addition to the company’s usual discussion of upcoming winter propane supplies.
Other utility companies will join Mann on Oct. 28 in assuring the commissioners that the systems are safe — especially the older pipelines.
Corporation Commission Chairwoman Kris Mayes said she’s confident that the commission’s annual inspections of natural gas pipelines protect the public, the Arizona Republic reported. However, Mayes wanted an update from the utility companies anyway, especially concerning maintenance in “high-consequence areas” near high-density developments.
“We have to be doing everything we can to make sure what happened there (in California) never happens in our state,” the Arizona Republic quoted Mayes.
Mann said SemStream hires the same independent company each year to inspect its pipelines and find any leaks with special sensors.
Mann said third-party damage, like someone digging to build a fence without calling the dig hotline, marks the most common source of a leak in plastic pipe. Sometimes, tree roots or a rock will threaten the pipe’s integrity.
“That’s part of why we do annual inspections,” said Mann. Plus, “people who are out walking or hiking will call us and say, ‘Gee I smelled the rotten egg smell.’”
The additive placed in gas to alert people to leaks smells like rotten eggs. Sometimes, a SemStream worker will investigate and discover a skunk accounted for the reported smell. “It might be a skunk,” said Mann. “Or, it could be your teenagers’ socks.”
SemStream receives calls from people reporting strange smells several times a week.
Whenever crews fix a leak, the company tracks it and places a pin on a map. Each year, SemStream officials look at the map and decide which sections of pipe to replace.
The last explosion locally occurred about two years ago. The house suffered severe damage, but nobody was home.
“With any energy source, you have to respect the potential power of the energy source,” said Mann. “That’s why it makes a good energy source.”
With over 2 million miles of underground gas lines crossing the nation, Mann says the number of incidents remains low.
“Usually when something happens, it’s a very large, robust front-page making incident,” he said.