The Santa Monica Pier is no longer where you’ll find the dirtiest ocean water in Los Angeles County.

In an annual ranking of the state’s most polluted beaches, environmental nonprofit Heal the Bay finds that Long Beach—specifically the segment of beach immediately west of Belmont Pier—had the county’s poorest water quality over the last 12 months. Statewide, only three other beaches scored worse on tests for E. coli and other bacteria harmful to swimmers.

It’s Long Beach’s first appearance on Heal the Bay’s list of “Beach Bummers,” though the city’s beaches frequently fail water quality tests during wetter winter months. During that time, stormwater and urban runoff flow into the Los Angeles River, which empties into the Long Beach harbor.

That doesn’t mean the beach is unsafe for swimmers year-round. According to Heal the Bay’s real-time report card, it scored an A-grade in its most recent water quality tests.

Because Los Angeles had a particularly wet winter this year, the river brought a regular flow of contaminated runoff to the shores of Long Beach, which affected water quality for much of the year. According to Heal the Bay’s annual report, that’s a big part of why the city’s beaches earned such lousy grades in the annual report.

Long Beach wasn’t the only beach where water quality suffered because of the stormy weather.

“The inordinate amount of rain during the winter months led to lower than average wet weather grades, and the lingering effects of the rain may account for the lower winter dry grades,” writes Heal the Bay water quality specialist Luke Ginger in the report. “Increased rainfall is also why we saw a decrease in the total number of beaches receiving perfect scores on our honor roll list this year.”

In Los Angeles County, only two beaches received perfect scores throughout the entire year: Las Tunas County Beach in Malibu and the oceanside stretch of Cabrillo Beach in San Pedro.

The latter beach is a telling example of how much environmental factors and the city’s built environment can affect water quality. The side of Cabrillo Beach facing San Pedro’s harbor was the eighth-most polluted beach in the entire state.

Separating the two sides of Cabrillo Beach is a long pier and a seawall, which helps to keep the waters calm in the nearby marina and the Port of Los Angeles. It also prevents water from circulating in and out of the harbor, trapping bacteria in the waters along the beach.

Adding to the grossness: Heal the Bay reports that recently upgraded sewage infrastructure at Cabrillo Beach has failed to stem an “unknown source” of human bacteria.

Joining Cabrillo Beach and Long Beach on the Beach Bummers list is Mother’s Beach in Marina del Rey, which ranked as the seventh-most polluted beach in the state. As in the harbor side of Cabrillo, the water at Mother’s Beach is relatively cut off from the ocean, making it difficult for bacteria to flow in and out of the marina channel.

Improving slightly since last year was the beach at Santa Monica Pier, which was named LA County’s most polluted stretch of oceanfront in 2017 and 2018. Water quality at the beach still received middling grades, but it wasn’t among the most polluted in the state—as it has been in six of the last 10 years.

What’s changed?

Heal the Bay communications director Talia Walsh says new infrastructure may have helped improve water quality slightly. In 2011 a new storm drain was installed, along with equipment to divert stormwater to a recycling facility. Last year, a new stormwater storage tank was added to prevent additional urban runoff from reaching the surf.