a map showing contaminated sites
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What the Mission District lacked in rich people, it made up for in gas stations.

Because the neighborhood was a major transportation corridor, “they were everywhere,” said Albert Lee, who handles many of the city’s cleanup cases as a senior inspector for the Department of Public Health’s Local Oversight Program.

The legacy of that bounty is contamination. Early tanks were built with steel that inevitably corroded and leaked. Other neighborhoods, like wealthy Nob Hill, also experienced contamination leaks, but theirs came from personal heating-oil tanks, Lee said.

A map of contaminated sites in the Mission shows 157 former and 15 ongoing sites. The contamination “plumes” come almost exclusively from older-generation underground storage tanks where gas stations stored gasoline, said Chuck Headlee, the underground storage tank manager for the SF Bay Regional Water Quality Control Board.

The old tanks were made entirely of steel and were single-walled, so they corroded and leaked easily. Moreover, they required no permit to install, said Headlee.

When California implemented its underground storage tank program in 1984, tank owners rushed to either retire or upgrade their old tanks.

As they dug up the tanks, owners discovered the majority of the plumes shown on the map, which includes all but three remaining plumes. Citywide, 95 percent of the 1,900 sites have been cleaned up.

“All the cleanup we’re doing is legacy stuff, from the older-generation tanks,” said Headlee. The newer tanks put in during the 1980s generally don’t leak.

The ongoing cases have simply been more difficult to clean up, said Headlee. All the remaining sites are being monitored, health officials said, and pose little threat of harm to human health, although they might affect property values.

The cleanups “zoomed in the 1980s [and] plateaued in the ’90s,” said Steven Hill, head of the State Water Board’s Toxics Cleanup Division.

Some of the city’s approximately 1,900 contamination cases involved multiple tanks, and more than 1,800 have been cleaned up, said Headlee.

Most cleanups, “the easy ones, you can get done in three to four years,” said Lee. But many of the remaining cases have taken over a decade to close, because of size or location.

Just locating a plume’s exact boundaries can be the toughest part of a cleanup case.

Once gasoline enters the groundwater, “it’s mobile,” said Lee. “When it rains, the groundwater rises; when it’s dry, the groundwater goes back down. So it can take a couple of years at least to locate the plume.”

Even if the plume isn’t mobile, it can be hard to get to. That’s the case at 401 Potrero Ave., where a 76 gas station and Potrero Test Only Smog currently stand. It’s an active and difficult site because it sits on top of bedrock.

At least three monitoring wells are necessary to triangulate a plume’s location, Lee said, but when the crew attempted to drill the wells at 401 Potrero in 2007 and 2008, they could drill only one, because of the bedrock.

“You run into underground electrical lines, sewer lines, water lines or fiber optics, or the well goes in, dries up, then you have to draw new plans up, and it takes six months to a year and another $5,000 to $6,000 to get another well in,” said Lee. “It goes on and on.”

Over roughly the next four years, the crew successfully drilled enough wells at 401 Potrero to map the plume. After analyzing well samples, Lee said, “in my mind, it’s ready for closure.”

At 793 South Van Ness Ave., the location of a former Shell gas station, Lee is still awaiting conclusive sample test results. Even though the case has been open for 15 years, “the plume hasn’t really been defined,” he said.

Three wells were not enough to map the complete contamination at the South Van Ness site, so the responsible party had to ask neighbors for permission to drill follow-up wells on their property, slowing the process.

The first wells were drilled in the late ’90s, and the last one roughly a year and a half ago, said Lee.

Cleanups can also be delayed by administrative mistakes. John O’Connell High School at 2355 Folsom St., for example, was the site of a 1998 heating oil spill. The school paid for an investigation, but the report was lost in the late ’90s, “probably on the way between them and us,” said Lee. If the report does not turn up, he will have to order a new investigation.

Sometimes the Department of Public Health closes a case, then reopens it years later. In 1986 it closed a case at PG&E’s Shotwell Complex, at 3235 18th St., because it decided the contamination was immobile, “capped” with asphalt and concrete to prevent direct human contact, according to the site’s lead caseworker, Stephanie Cushing.

“In some cases, remediation isn’t possible,” and the city can only mitigate the contamination’s effects on human health, Cushing said. Hence the concrete cap.

The department put a deed restriction on the property that required PG&E to reopen the case if it wanted to break through the cap for any reason. PG&E did just that, hoping to map the plume’s specific boundaries and locate an unaffected area to safely install an elevator, said Cushing. The case is still open.

When a gasoline plume is discovered, the owner of the contaminated property foots the bill. The health department can file a criminal case against owners who don’t comply, or charge them $1,000 per day under the water code, said Headlee.

But most do comply, he said, because California has a fund that reimburses owners for removing the tanks.

Statewide, about 8,000 underground tank sites are currently being cleaned up, and about 3,500 are covered by the state fund, said John Russell, assistant deputy director of the Division of Financial Assistance at the State Water Resources Control Board.

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  1. Thanks again for covering this. I live across the street from one of the “still being monitored” sites. You guys do great work.

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