Highlights
-
Stormwater runoff is the rainwater that washes off landscapes, including cities, and flows towards water bodies. It’s a major pathway for many contaminants to reach San Francisco Bay.- SFEI’s stormwater monitoring team has grown and is innovating techniques to further expand its sampling abilities.
- SFEI’s studies of microplastics, forever chemicals, and other emerging contaminants have been influential in the Bay Area and globally.
In January 2017, a steady downpour bathed San Jose for three days straight. While most of the city hunkered down, Alicia Gilbreath crouched on the banks of the Guadalupe River to collect water samples every four hours through the day and night.
“It rose ten feet,” she recalls. “To watch the vegetation and trash coming down, the change in the river—that water is really powerful.”
Because Gilbreath was a whitewater rafting guide long ago, she appreciates the water’s power. But for decades, she’s been interested in the surges of stormwater for another reason: to track how contaminants arrive in San Francisco Bay, and to find where they come from.
Gilbreath now leads SFEI’s stormwater team. What began as efforts to study mercury and PCBs (banned industrial chemicals) has grown into a major branch of SFEI’s Clean Water program and the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP). The team now routinely breaks new scientific ground for the Bay Area—and sometimes far beyond.
“There’s not a ton of literature on the concentrations of contaminants in stormwater collected during actual storm events, when the large majority of the pollutant load runs off from urban areas,” says Gilbreath. “So we can’t just draw on data from the rest of the world. We have to generate it to understand the pollutants that we’re interested in.”
An Emerging Focus
Two important Bay Area studies in the last decade heightened the focus on stormwater. In 2016, RMP scientists compared water samples from three distinct areas of San Francisco Bay: near a wastewater treatment plant, by the agriculture-influenced Napa River, and in San Leandro Bay, which receives runoff from Oakland and its surrounding highways. Laboratories scanned the samples for under-the-radar chemicals like less-studied pesticides, industrial chemicals, or plastic additives. The samples from San Leandro Bay “had the most diverse contaminant signals and a lot of distinctive tire related chemicals,” says Rebecca Sutton, the lead scientist for emerging contaminants at SFEI.
“It really made us zero in on stormwater as something that the whole world needs to pay more attention to when it comes to emerging contaminants,” she says.
A few years later, the San Francisco Bay Microplastics Project revealed that trillions of microplastic particles reach the Bay each year via storm drains—mostly in the form of car tire particles and synthetic fibers. The microplastics from stormwater dwarfed every other pathway studied. Other studies have since found that stormwater carries other contaminants, including PFAS and anti-microbial chemicals called QACs, at concerning levels.
“It’s all pretty groundbreaking stuff,” says Chris Sommers, the program manager for the Santa Clara Valley Urban Runoff Pollution Prevention Program. “It’s not something that a countywide stormwater program would necessarily take on by itself.”
Stormwater sampling for unregulated and less-monitored emerging contaminants has now blossomed into a major focus at the RMP, in part to fill gaps in basic knowledge. So far, SFEI’s scientists have found significant amounts of forever chemicals, plastic additives, microplastics, car tire chemicals, pesticides, antimicrobial compounds, and many other contaminants in urban stormwater runoff. But because there’s no easy for way know what chemicals many products in the built environment contain, finding the specific sources of these chemicals can be daunting.
“It’s a lot of detective work that’s really quite tricky,” says Sutton.
Chemicals can also transform when exposed to sun, air, and water. Even when it’s possible to determine which chemicals are in products used outdoors—from cars to construction supplies—they might not match the compounds scientists detect after leaching, weathering, or breaking off the original products and traveling through the environment.
That’s exactly how a team of scientists, including from SFEI, solved the mystery of coho salmon dying en masse in Washington. The chemical they identified, called 6PPDQ or “6Q,” was so toxic to coho that a few drops in an Olympic swimming pool would be fatal. It wasn’t an ingredient sold on the market, but a transformation from another chemical in car tires.
Storm By Storm
Sleuthing for unknown chemicals isn’t the only challenge stormwater scientists in the Bay Area face. Storms with adequate rainfall are rare enough that when they arrive, it’s all hands on deck—regardless of whether it’s the middle of the night or holidays. Every drop of data is valuable.
“Suddenly it starts raining and you have to be out there soaking your butt off at like 1:00 a.m.,” says Don Yee, who estimates he’s spent 50 nights sampling stormwater over the last decade. “It’s kind of fun the first few times, but somewhere into the fifth or sixth hour, you’re saying, ‘I can’t wait to get home and take a nice warm shower.’”
Gilbreath has been there too. “It’s pretty labor intensive to monitor stormwater,” she agrees. “We can’t monitor everything.”
That’s why the robots got involved.
To be continued…
This article is part one of a special feature series on stormwater. Come back next month for part 2!
