Stormwater is the Largest Source of Bay Pollution

Storm drain clogged with trash and debris.
Storm drain clogged with trash and debris.
Photo Credit: Mike Dillon.

Storm drains prevent flooding by draining excess water out of our neighborhoods, streets, and highways and carrying the water through pipes and culverts to nearby creeks that lead to the Bay.

Unfortunately, a lot more than just clean rain water flows to the Bay through our storm drains.  Last week a clogged plastic sewer pipe in Sausalito caused more than 50,000 gallons of raw sewage to spill into San Francisco Bay.  The sewage ran across the sidewalk, into a gutter, and down a storm drain that leads to the Bay 40 feet away.

While incidents like this happen from time to time and generate coverage in the news, storm drains carry toxic pollutants and trash into the Bay literally every time water flows through them.

Contaminants

The recently released “Pulse of the Bay” report found chemicals like pesticides, insecticides, and flame retardants in San Francisco Bay at levels that could pose hazards to aquatic life.

Pollutants enter the Bay through a variety of sources, including wastewater treatment plants, factories, and agriculture.  But according to the San Francisco Bay Regional Water Quality Control Board, stormwater is now the largest source of surface water pollution to Bay area waters.

Much of this pollution comes from our streets.  Cars discharge harmful metal particles like lead, zinc, and copper, and leak more oil into the Bay each year than the Cosco Busan oil spill did in 2007. Even the streets themselves contribute directly to the pollution problem.  Asphalt is held together with “recycled” petroleum products and waste from refineries, byproducts that would otherwise require safe disposal.  These toxic substances and the sealants used to coat paved surfaces leach into our waterways over time.

Trash

At this year’s annual Coastal Cleanup Day on September 21st, volunteers got to see first-hand how trash enters the Bay through our storm drains and creeks.  First Flush, the first big rain of the season, washed trash from the streets right into the creeks and wetlands we were cleaning up.

Some streets and highways are so full of litter that storm drains become clogged with trash and other debris, resulting in flooding.  Caltrans spends $50 million each year picking up litter on the streets, and has invested more than $5 million in the last five years to improve drainage on Highway 101 and I-80.

Plastic bags and Styrofoam food containers are some of the biggest offenders, which is why we’ve prioritized plastic bag and Styrofoam bans throughout the region over the past several years.  Recently we’ve turned our attention to the nearly 3 billion cigarette butts littered in the Bay area each year.  We’re investigating the best local policy options to address the largest single source of litter in the Bay area.  In the meantime, we’re also calling on tobacco companies to take responsibility for the toxic litter they produce.  Sign our petition to tell tobacco companies – Keep you butts out of our Bay!

Learn more about water pollutants and how you can help keep our Bay clean and healthy.