When a rain-soaked hillside gave way, threatening two 16-inch transmission lines that serve 250,000 residents in California’s Marin County, Pacific Gas & Electric’s gas team faced a tall order: Engineer and execute a creative bypass plan fast enough to avert a catastrophic service interruption, and get it done safely before the next round of storms was due to arrive.
It was still raining the evening of Tuesday, March 21, when PG&E learned that the pipelines might have been compromised in a landslide triggered by a “bomb cyclone”—a torrential storm that had saturated parts of California, including Marin County north of San Francisco.
The extent of the impact to the lines wouldn’t be known until the next day, when a PG&E team could gather at the site to assess the situation. But utility executives knew the worst-case scenario— in which both pipelines were deemed unsafe and had to be shut down—would be catastrophic. The lines, which were buried near the top of a hillside overlooking Highway 101 in Novato, were the sole source of natural gas for the entire county. If the lines became compromised, estimates of how long it might take to restore service were daunting.
“We were talking weeks or months to get everybody back in service, even with a mutual aid effort,” said Chris Warner, senior director of gas transmission engineering and integrity for PG&E. “The number was so big, we knew we needed to do everything we could to ensure it didn’t happen.”
It soon became clear that something had to be done—and fast. In a matter of days, the next in a series of storms that had soaked the region for months was forecast to arrive. The rain could further destabilize the soggy hillside and jeopardize efforts to keep gas flowing uninterrupted to Marin County.
What PG&E achieved over the next five days—from the initial news of the landslide to the completion of a temporary bypass skirting the landslide area—is a testament to extraordinary teamwork, unparalleled dedication to safety, the value of strong community ties and some good old outside-the-box thinking.
PG&E’s electric workers first realized the potential threat to the gas lines when they were dealing with downed power lines in the area. Although there was no blowing gas or loss of pressure that would indicate a rupture, the discovery triggered activation of PG&E’s Gas Emergency Center and Incident Management Team, freeing Warner and other members of the team from their day-today responsibilities to focus on a situation that had the potential to develop into a full-blown crisis.
The morning of Wednesday, March 22, the team members, supported by geoscientists, were at the scene. What they were able to see was not promising. The lines, originally installed about 10 feet apart near the top of the area where the landslide occurred, were now separated by twice that distance.
The lower pipeline had been pushed down the slope and buried in the slide. The weight and force of the slide had bent the pipe at an angle of 45 to 60 degrees. The upper pipeline appeared to be in its original location and intact. With the large deflection, PG&E quickly decided to shut down the lower pipeline. Thankfully, the twin lines had been installed in 2013 with redundancy in mind. If one had to be shut down for maintenance or due to damage, gas planners knew the other one provided sufficient capacity to maintain service to Marin County.
The $64,000 question: Was the situation static or dynamic? The answer from PG&E geoscientists, among the first on the scene, was not comforting: The landslide was still active and continuing to move slowly, with the potential to damage the upper pipeline and force PG&E to shut it off as well. The incoming weather created concern that a section uphill of the still-active line could fail and take the remaining line with it.
Beyond the potential for a massive and prolonged service outage, immediate safety concerns added to the urgency of the situation: A pipeline rupture could send pieces of pipe and other debris hurtling down the hillside toward the heavily traveled Highway 101.
While the need for a bypass was becoming more apparent by the minute, the immediate focus turned to monitoring the pipelines and the movement of the slide. In addition to the geoscientists, PG&E relied on a variety of technologies to collect critical information and to mitigate further damage.
Aerial drones equipped with cameras were deployed hourly to visually inspect the condition of the pipelines. Four times a day, remote laser leak detection equipment was used to spot gas leaks. When weather allowed, a plane with lidar, or light detection and ranging, technology accurately measured the daily movement of the slide.
When safety concerns about the continued movement of the slope precluded any buttressing to secure the area around the remaining pipeline, PG&E assessed other ideas to minimize slope movement. PG&E workers dropped pumps into the area above the lower pipeline where stormwater was ponding to prevent water pressure from building up and potentially causing the slope to slip further.
By the end of the day Thursday, the focus of the incident response could shift from mitigation to finding a way to bypass the compromised section of pipe. Never far from team members’ thoughts was the ominous forecast of another storm bringing torrential downpours as early as Monday night—just four days away.
“The concern was escalating because we knew there was another atmospheric river event coming,” Warner said. “We had to get something done quickly. Otherwise we were concerned we might have another slide that would take out the remaining pipeline.”
Neither of the most obvious routes for bypassing the slide area— going uphill above the impacted area or below the bottom of the slide—were ideal because of additional risks they would pose or the time they would take, said Bill Meredith, PG&E’s general construction gas transmission director.
Meredith recalls standing on the hillside with a group that Friday afternoon, March 24, all wondering how they could make the uphill option work. Then construction supervisor Sam Niegel looked downhill toward Highway 101 and suggested an alternative: Why not put it in the center median?
PG&E’s Gas System Planning department quickly analyzed the loads and determined that an 8-inch pipeline would be sufficient as a temporary bypass. Implementing Niegel’s plan would require running the 8-inch pipe from one of the tandem 16-inch pipelines north of the slide area, under the southbound lane of Highway 101, then above ground for 1,900 feet through the median, then back under the highway south of the slide area and tying back into the 16-inch line.
The idea initially met with skepticism: Nobody thought the California Department of Transportation, or Caltrans, would approve a plan that called for running a natural gas pipeline down the median of a busy freeway—and shutting down the highway for most of a day to do it.
“At first, we kind of looked at him like he was crazy, but it was an outstanding plan,” Meredith said. “When he said it, I said, ‘Let me get on the phone and see what we can do.’”
The plan made sense. Using an 8-inch pipe would require fewer welds, saving precious time. Running the pipe above ground would shave at least a day off the project. And serendipitously, the median already was blocked off by construction barriers thanks to an ongoing Caltrans project.
That Friday evening, Austin Hastings, GEC director, raised the idea in the County Incident Management call. “The call started at 6 p.m., and by 7:30 p.m. I had agreement to proceed,” Hastings said. “I was so grateful for the teamwork and support.”
Caltrans had questions, but members of the PG&E response team were pleasantly surprised by both the agency’s willingness to work hand in hand with the utility to expedite the project and the level of cooperation from all the local and state agencies impacted by the plan.
“People were singularly focused on how we could work together to eliminate the risk of the pipeline rupture, do the work safely and ensure Marin was able to continue to access natural gas,” Warner said. “The teamwork and support were incredible and a highlight of my career.”
Warner and Meredith credited the trust and relationships built over the years by PG&E’s community affairs and communications teams—and effective communication with residents about the impact of the landslide and how the bypass project and resulting traffic detours would affect them.
“I think the success, really the key to this, was complete outsidethe-box thinking and just wanting to make this work and get the bypass installed and tied in before the next storm came in,” Meredith said.
With Caltrans’ approval, Meredith and his construction crew spent Saturday, March 25, building sections of the bypass from the 16-inch transmission line down the hill to the Caltrans right of way. At 9:30 p.m., after a 30-minute delay to let an ambulance through, the roadblocks went up and Highway 101 was shut down.
It was just over 48 hours before the next storm was due. Given the aggressive timeline and the amount of work involved, Meredith decided to split his crew of about 100 workers into two shifts and work around the clock, with some 20 light towers illuminating the median for the night shift.
Working nonstop, crews trenched across the southbound lane of Highway 101 on both sides of the area affected by the landslide, then set to work installing the 1,900-foot section in the median. The rains had turned the ground into mud, impassable for the utility’s welding trucks, but a contractor offered its Morooka rubber track crawler carriers—basically off-road dump trucks on tracks— to haul the welding equipment into the median.
By the next morning, the crews had completed the bypass installation. After several hours to allow the concrete and patching of the trench lines to cure, Caltrans was able to reopen the freeway at 2:30 p.m. Sunday, March 26—about 17 hours after it was shut down.
As luck would have it, the rain moved in a little earlier than predicted. But by then, the bypass had been completed—2,350 feet of 8-inch pipe—and hydrostatic testing had confirmed the strength and integrity of the new pipeline.
It was 3:30 a.m. on Tuesday, March 28, when crews tied the bypass into one of the 16-inch transmission lines on either side of the slide area and shut off gas to the section of pipeline that had kept gas flowing to Marin County. A project that by IMT incident commander Rich Yamaguchi’s reckoning could take more than a year had been completed in less than a week.
“It’s amazing we were able to come up with and execute this within a couple of days,” Yamaguchi said. “To be able to pull this off is just historic.”
The design and construction of the permanent replacement pipeline could then proceed at a more leisurely pace. Both 16-inch pipelines were rerouted through an area below the slide area but drilled deep under the slide so they shouldn’t be affected by any future landslides. The first replacement was tied in on April 28 and the second on June 15.
An estimated 200 PG&E employees and contractors participated in the emergency response in Novato—from the initial assessment and monitoring of the affected pipelines through construction of the bypass and permanent replacements—often under precarious, if not downright dangerous, conditions.
Nobody got hurt.
“One of the things we’re most proud of is that we had no injuries in monitoring or assessing the issue, no injuries in building the bypass and no injuries in putting in the final replacement sections,” Warner said.
He pointed to the early engagement of PG&E’s safety department and the expertise of the company’s geosciences team as two key factors in keeping the response effort injury-free, along with the ability to leverage training and PG&E’s deep experience managing through previous emergencies.
A key strategy was keeping employees out of the active slide area itself and having geoscientists accompany workers who had to be on the hill for any reason. Technology—the drones and airborne lidar system in particular—played an important role by providing the means for safely monitoring the condition of the still-active slide and the condition of the in-service transmission line at regular intervals throughout the completion of the bypass.
Fatigue was one of Meredith’s biggest safety concerns. To keep crews sharp, short briefings or “tailboards” were held at the beginning and end of each shift to make sure workers understood the safety hazards at the worksite and what they needed to accomplish during the next shift. Meredith also noted that geoscientists were on-site 24/7 for the duration of the construction project, in addition to a safety officer and field safety specialists “completely focused on overseeing safety and identifying hazards and supporting our crews to mitigate those.”
Of course, there’s always room for improvement. One of Warner’s key takeaways from Novato: While it’s human instinct to want to jump into action immediately—to “just go out and take a look at the pipe”—it is important to pause and consider worst-case scenarios and develop sound safety strategies.
Still, Warner and colleagues can take a bow for their role in not only averting a major service outage but living up to PG&E’s stated commitment to its No. 1 priority: “Everyone and everything is always safe.”
“It went flawlessly,” Meredith said. “I think back on all of the emergencies I’ve been on over the 20 years I’ve been here, and I can’t think of one that went better.”