Seattle Schools knew there was methane gas beneath its new high school - but skipped some safety measures

Before Seattle Public School spent $300 million to rebuild Rainier Beach High School on a peat bog, scientists hired by the district warned that methane in the soil could pose an explosive problem if it were to leak into the school.

The scientists recommended several standard safety measures to prevent that from happening. But a KUOW investigation found that Seattle Public Schools skipped some of those safety recommendations.

The school’s campus was part of Lake Washington until engineers lowered the lake in 1916, leaving rich deposits of organic matter. Peat soil is notoriously tricky to build on, and before the building opened to students last April, its foundation had already settled unevenly, and far more than predicted — one hazard of building on peat.

The decaying plant and animal matter in peat also emits methane gas. Methane isn’t highly toxic to breathe, but it is highly flammable.

The absolute risk of an explosion at Rainier Beach or any building is impossible to know given all of the factors at play, according to Kelly Pennell, a civil engineering professor at the University of Kentucky who has spent two decades studying how to keep hazardous soil vapors like methane from seeping into buildings.

Pennell, who was not involved in assessing Rainier Beach High School, said engineers recommend vapor mitigation to get unknown risks closer to zero.

“What we're looking to do is to prevent the possibility of an explosion,” Pennell said.

Methane gas igniting underground has caused some of the world’s biggest coal mine disasters. Though above-ground explosions are uncommon, they do happen: In 1985, methane blew up a Ross Dress-for-Less store in Los Angeles.

Before construction began at Rainier Beach, the school district hired environmental engineering firm Maul Foster Alongi to “assess vapor intrusion risk posed by a natural peat layer present beneath the proposed future school,” the firm said in a January 2022 report to the district. It warned that methane is colorless, odorless, lighter-than-air, and a potential fire and explosion hazard.

When scientists measured methane in the ground at six locations on the footprint of the planned school, they found “at least one location with methane concentrations above the 5 percent lower explosive limit,” Maul Foster Alongi told the district in its report, and recommended “employing measures to mitigate for the potential for methane gas to intrude into the future building.”

Engineers advised the district to follow the Environmental Protection Agency-recommended vapor mitigation standard: sealing the foundation with a 60-millimeter hazardous vapor barrier to prevent methane from sneaking into the building, as well as installing an underground gas venting system to funnel methane away from the school, and conducting monthly methane tests once the school was built — and before opening to students.

However, the district did not install the recommended methane vapor barrier. And it didn’t start testing for methane at the school until last month — after KUOW inquired.

The district did install methane vents that lead from beneath the building to the roof, as engineers advised, said Richard Best, the district’s director of capital projects and planning. “It's like a plumbing system,” Best said. “It's just capturing the gases that are being released by the peat soils, and taking it around the building, and dispersing it up above into the atmosphere.”

But the district did not follow engineers’ recommendation to seal the foundation with 60-millimeter material designed to prevent methane leaks. Instead, the district installed a 1.2-millimeter waterproofing barrier under the building to keep the foundation dry.

Mike Skutack, the district’s project manager for the Rainier Beach High School rebuild, said the district missed the hazardous vapor barrier recommendation in the methane report it commissioned.

“We're not aware of a methane mitigation that required anything more than the grid of piping that passively releases the methane above the building,” Skutack said.

Neither did the district monitor for methane at the school before opening it to students last April — despite that safety measure appearing in boldface type in the engineers’ report to the district.

Tina Christiansen, district spokesperson, said monitoring had not begun because construction is still underway on the school’s new performing arts center. But she also said that the district “missed” the recommendation to test before the school opened to students.

Christiansen said that after KUOW pointed out that safety recommendation, the district had its environmental health services director test for the first time last month throughout the school, including the gym, skills center, and commons, and found no methane gas.

“That wouldn't necessarily be reassuring to me,” said Pennell, the civil engineering professor.

The gas monitor the district used, a consumer model by the brand CHDNAKS that sells for $65 on Amazon, gives a reading for “explosive gases,” which on gas monitors typically includes methane. However, it does not specifically indicate methane levels.

“It's pretty easy to buy a gas monitor and to look at readings,” Pennell said. But knowing how to accurately test for hazardous vapors — and interpret the readings — is far more complex, she said. “In my experience, I haven't seen people be able to do it themselves, especially out of the gate."

Pennell said hazardous gas monitoring in this case should test specifically for methane, and be carried out in the first year by highly trained experts who’ve designed a site-specific monitoring plan. That should include testing places close to the foundation, where cracks could let in methane, and small spaces at the school that might be poorly ventilated, she said.

In King County, the law requires builders to follow engineers’ methane mitigation plans on new construction when building near landfills with methane gas from decaying garbage. The law doesn’t require mitigation on sites with methane from decaying peat bogs – like the one under Rainier Beach.

Pennell said methane safety laws are frustratingly inconsistent. She said that’s most problematic on construction projects like schools, where safety is critical but budgets are often limited.

“By the time you're putting down something like a vapor barrier or a mitigation system, those are places that maybe you're cutting costs. That should not be the place where you're cutting costs,” Pennell said.

Inside the new school is a tribute to Rita Green, a Rainier Beach alumnus. She’s a longtime advocate for equitable education in the district, with a focus on this school, which has 96% percent students of color – more than any other high school in Seattle.

Green and other advocates had protested for years that the school was repeatedly passed over for modernization and threatened with closure.

When the district opened Rainier Beach High School to students last April, it heralded the sparkling new building — which seats twice as many students as the old building — as an investment in equity.

But community distrust remains.

“It wouldn't surprise me that the district would cut corners on anything for Rainier Beach High School, given its current demographics, meaning students and families of color,” Green said.

Green sat on the district’s community design team for the new building. At the meetings she attended, Green said methane never came up. If it had, she says, the community would have insisted that the district follow every recommendation to keep students safe.

Green is skeptical of the district’s claims that there’s no methane in the school.

“I wouldn't trust the district to say we tested it without a methane specialist saying these are all the areas you need to test,” Green said.

Now, Green says, the district needs to bring the school community and scientists together to make sure Rainier Beach High School stays methane-free.