Troubled Waters: What’s Really Lurking Off Santa Monica

Bacteria advisories, mystery storm drains, and the truth behind that unmistakable low-tide funk — a paws-on guide to Southern California’s dirtiest and cleanest shorelines.

If you’ve walked the Santa Monica Pier this year and caught a whiff of something distinctly unglamorous, your nose was not lying to you. Santa Monica’s shoreline has spent much of 2026 cycling through bacteria advisories, and the pier itself has landed on California’s statewide “Beach Bummers” list as one of the most consistently polluted stretches of coastline in the state. This is not a one-off scare. It’s a chronic, well-documented condition of one of the most photographed beaches in America — and it says something uncomfortable about the infrastructure sitting just out of frame.

The Santa Monica Problem, By the Numbers

Los Angeles County’s public health department has issued repeated ocean water warnings at Santa Monica beaches throughout the year, most consistently clustered around a handful of exact spots: the Santa Monica Pier itself, the Pico-Kenter storm drain, the Montana Avenue storm drain, and the Santa Monica Canyon Creek outlet near Will Rogers State Beach. Each advisory follows the same pattern — a 100-yard buffer zone up and down the coast from the drain or creek mouth, closed off until follow-up testing shows bacteria levels back within state limits.

The pattern repeated itself in January, February, and March advisories this year, and the annual scorecard confirmed it wasn’t a fluke: Heal the Bay’s 2025–2026 Beach Report Card ranked Santa Monica Pier as the second-most-polluted beach in the entire state of California, and the worst in Southern California, edged out only by the Tijuana River mouth near the U.S.–Mexico border. It’s a distinction the pier has earned repeatedly in past years too, prompting the City of Santa Monica and Heal the Bay to form a joint task force dedicated purely to hunting down the pier’s contamination source.

What’s Actually Causing It

The short answer is fecal indicator bacteria — organisms like E. coli and enterococcus that signal the presence of human or animal waste in the water. They don’t come from one dramatic sewage spill; they come from an accumulation of chronic, boring infrastructure failures:

• Storm drains. Nearly every hotspot in the county traces back to a storm drain or creek outlet. Storm drains carry street runoff — motor oil, pet waste, trash, lawn fertilizer, and yes, leaking sewage — directly to the ocean, completely untreated. Unlike sewage, storm runoff isn’t filtered before it hits the sand.
• Aging sewage infrastructure. Much of the pipe network under Los Angeles County predates modern building codes. Cracked or undersized pipes let sewage seep into groundwater and storm systems, especially during heavy flow periods.
• Rain. A single storm can flush months’ worth of accumulated street pollution into the bay in a matter of hours, which is why bacteria counts spike hardest in the 72 hours after rainfall.
• Bird droppings. The Santa Monica Pier in particular struggles with bacteria linked to the large gull and pigeon population roosting on the pier structure itself, directly above the water.
• Wildfire runoff. The Los Angeles wildfires that broke out in January 2025 sent ash, heavy metals, and debris into the watershed, and Heal the Bay’s water-clarity testing found the effects traveled from Malibu’s Surfrider Beach down through Dockweiler, well beyond the original burn zone.
• Poor water circulation. Enclosed or semi-enclosed swim areas — like Mother’s Beach in Marina del Rey — trap bacteria instead of letting tidal flow disperse it, which is why that entire swim area has spent stretches of this year under a blanket advisory.

Other Contaminated Spots Around L.A. County

Santa Monica gets the headlines, but the same 2026 health advisories have repeatedly named several other Los Angeles-area locations:

• Will Rogers State Beach, near the Santa Monica Canyon Creek outlet
• Topanga County Beach, at the Castlerock storm drain
• Topanga Canyon Beach in Malibu, near the lagoon
• Malibu Lagoon at Surfrider Beach, near the public restrooms
• Puerco Beach, at the Marie Canyon storm drain
• Escondido State Beach, at the Escondido Creek outlet
• Mother’s Beach in Marina del Rey (its entire swim area)
• Venice, near the Topsail Street storm drain extension

Statewide, San Diego County’s beaches near the Tijuana River — Border Field State Park and Imperial Beach — remain the worst in California by a wide margin, driven by cross-border wastewater flow that has plagued the region for years.

Why the Water (and the Air) Smells Like Poop

That distinctive low-tide funk near a storm drain is not your imagination, and it’s not always the same culprit. There are two separate — and equally unpleasant — chemical stories happening at once.

The sewage smell

When bacteria break down organic waste — actual sewage, pet droppings, or decaying organic street runoff — anaerobic bacteria produce hydrogen sulfide gas as a byproduct. Hydrogen sulfide is the same compound responsible for the classic “rotten egg” smell, and it’s released directly at the point of highest bacterial activity: storm drain outlets and creek mouths, exactly where the advisory signs go up.

The algae smell

Separately, Southern California has periodically dealt with algae blooms — sometimes the same reddish-brown “red tide” blooms responsible for nighttime bioluminescence. When that algae dies off en masse, it also releases hydrogen sulfide as it decomposes, creating a smell Heal the Bay Aquarium staff have described as closer to rotting fish. Both processes point to the same root cause: excess nutrients (fertilizer runoff, sewage, urban pollution) feeding rapid biological growth that then rots.

What those yellow warning signs actually mean

The bright yellow or orange signs posted along the sand aren’t decorative, and they’re not always saying the same thing:

The signs cluster around storm drains and creek mouths because that’s where indicator bacteria concentrate most heavily — testing consistently shows counts drop off the farther you get from a drain, which is the entire logic behind the 100-yard buffer zones.

How to Avoid Getting Sick

Where It’s Actually Safe to Swim

The good news buried in all this: the overwhelming majority of California’s coastline still earns strong marks. Statewide, roughly 91% of beaches pulled an A or B grade during dry summer weather this year, and Los Angeles County alone placed several beaches on Heal the Bay’s Honor Roll — the annual list reserved for locations that post excellent grades across every testing season, wet or dry.

The pattern holds county to county: open, well-circulated stretches of coast with less urban runoff funneling in — Malibu’s northern beaches, the Palos Verdes Peninsula — consistently outperform beaches sitting downstream of dense storm drain networks. Orange County, further south, has topped the statewide Honor Roll for consecutive years running, with dozens of beaches posting perfect grades.

Water quality is not a fixed label — it shifts week to week with rainfall, tides, and runoff, which is exactly why officials keep repeating the same advice: check the current grade before you go, not the reputation the beach had last summer.