Here's How a Major East Bay Sewage Leak Could Harm Fish and Wildlife

A sewage leak that has spilled an estimated 20 million gallons of wastewater into a Contra Costa County wetland could have considerable ecological consequences for the fish and wildlife populations that call the Suisun Marsh home.

Among the water that runs through our sewage system is washed-out shampoo, sudsy dish soap and remnants of medications — and all of those can be harmful to the fish and birds, according to Sejal Choksi-Chugh, the executive director of ecological watchdog Baykeeper.

The leak was discovered Monday, spurring repair efforts this week, but it is believed to have started weeks earlier. Choksi-Chugh said she worries about how the influx of untreated water that has seeped out of the Delta Diablo Sanitation District’s broken pipes will affect the environment.

“When you’ve got a lot of this wastewater discharging in concentrated levels in an area like that, we’re going to see some exposure to chemicals that are in wastewater,” Choksi-Chugh said. “That’s going to have an impact; whether or not we see that impact in this generation of fish and wildlife or in their next generation is something that we would have to see.”

Choksi-Chugh said her first reaction to news of the leak was pretty much the same as everyone else’s: “gross.”

But it’s not necessarily the bacteria or human waste that’s the most concerning to her. Chemicals that people use all the time — to make our laundry smell good, cure fall allergies and clean our homes — can be really detrimental to animals’ health.

Anti-inflammatory drugs like Advil can impact aquatic animals’ organ functions and damage their cells. Other common pharmaceuticals like allergy and cholesterol medications and hormone therapies have similar effects.

Chemicals in many of the soaps we use are also dangerous for animals. Choksi-Chugh said that these can act as endocrine and reproductive disruptors, which can cause population harm that doesn’t show up right away.

“You sometimes see immediate impacts with a big fish kill or something like that, but more likely, we will see endocrine disruption or reproductive disruption or neurological problems,” she told KQED. “We might see deformed fish in the future or impacted fish just not having as many babies in the future.”

The Suisun Marsh area is especially vulnerable because of its location — the water there is a mix of saltwater from the Pacific Ocean and incoming freshwater from the Sacramento and San Joaquin rivers, whose delta is just to the east.

Because of the unique brackish environment, it’s where a lot of fish and wildlife populations choose to make their homes. Choksi-Chugh said the area is highly sensitive and one of the most important habitats on the West Coast.

It’s also along the migration route for many bird species, which follows closely to the Pacific Highway. Birds stop for water and prey and interact with the ecosystem there regularly, so any ecological fallout from the sewage leak there could carry on down the line.

It is important to put in context how much wastewater has actually spilled. Twenty million gallons sounds like a ton, but the Suisun Bay is also 116,000 acre-feet of marsh, wetlands and uplands.

The spillage reported so far is equal to about 60 acre-feet of water, which Choksi-Chugh said is considerable, but not huge. It’s also still not clear how much wastewater may have made its way from the marshland into the Suisun Bay. Results from initial water quality tests the sanitation district ordered Tuesday were still pending as of midday Thursday.

What’s more concerning than the size of the spill, Choksi-Chugh said, is that it was likely preventable, and more needs to be done proactively to prevent similar leaks as the Bay Area’s infrastructure ages.

Delta Diablo began looking for a leak after noticing weeks ago that there was reduced inflow into its treatment plant. The wastewater was difficult to spot because of the marshy cover in the area where it was ultimately identified.

“​​There are ways to be more preventative than that,” Choksi-Chugh said. “Oftentimes we will ask cities to look at doing regular operations and maintenance on their pipes because we want them to understand where the areas that are corroded and have the possibility of leaking and breaking are.”

Vince De Lange, the general manager of Delta Diablo Sanitation, said the district does routine maintenance, but the specific pipe where this leak occurred is buried underground and isn’t easy to do maintenance on, since it is always in use. Until this week’s repairs, which included an above-ground bypass system to bring wastewater from one pump station to the next gravity pipe, there was no way to send wastewater another way to the treatment plant.

The other thing they can do is increase storage capacity at the pump stations along the route to the treatment plant.

While doing the repair work, Delta Diablo temporarily stopped the leakage by using the storage at the nearby Shore Acres pump station. It can hold up to 800,000 gallons of water, which is a little less than the amount that flows through on an average day.

De Lange said that between the storage station and sewer cleaning trucks sucking water out of upstream pipes, they were able to stop the leak for about 22 hours before Shore Acres reached capacity.

“Given the fact that we are seeing more extreme weather events, including larger rain events that can impact the amount of water that’s in the wastewater system, it makes it more important than ever to think about excess storage capacity, making sure that we’re not putting ourselves in a situation where these kinds of discharges become more regular,” Choksi-Chugh said.