Time to Rethink the 3-Day Rain Advisory Rule
The 3-Day Rule has long been a mantra at Heal the Bay – always wait three days after a rainstorm before getting back into the ocean.
But a recent study conducted by UCLA environmental science students in conjunction with Heal the Bay’s water quality team indicates that extra caution may be warranted at certain locations, especially stormdrain-impacted beaches and enclosed beaches.
The new report, which analyzed Heal the Bay’s beach water quality data for the past seven years, reveals that many popular beaches near stormdrains in Southern California remain riddled with bacterial pollution up to five days after rain and pose a health risk. There are more than 100 stormdrain-impacted beaches in Los Angeles and Orange Counties.
Malibu Surfrider, Santa Monica Pier, and Doheny are among the iconic Southland beaches located near flowing storm drain outfalls. These outfalls carry bacteria-laden urban runoff directly from city streets into the sea. So it seems wise to avoid these beaches for at least 5 days after a storm.
The main source of pollution to Santa Monica and San Pedro bays is urban runoff carried through the county’s 5,000 mile-long storm drain system. Unlike sewage, this runoff typically receives no treatment and flows freely onto shorelines and the sea through the network of open channels, catch basins and streams.
Exposure to bacteria from runoff can cause a variety of illnesses, most frequently respiratory infection and stomach flu. Human pathogens of unknown origins can also be carried down gutters.
Separately, enclosed beaches located near harbors and marinas often did not meet beach water quality standards for 10 days after a rain, according to findings from UCLA undergraduates participating in a program with the school’s Institute of the Environment and Sustainability.
Enclosed beaches, such as Marina del Rey’s Mother’s Beach or L.A.’s Cabrillo Harbor, do not have the strong currents and breakers of open-ocean beaches. The lack of waves may be reassuring to some parents but it leads to very poor ocean circulation.
Students analyzed water quality data gathered weekly by Heal the Bay with the goal to re-evaluate the California Department of Public Health advisories. More than 87,000 data points from the 32 most frequently monitored beaches in California were analyzed for levels of harmful bacterial pollution.
“The UCLA study indicates that the 3-Day Rule may not be adequate to protect the health of all ocean swimmers,” said Amanda Griesbach, a Heal the Bay staff scientist. “Until the rule is modified, swimmers are better protected by avoiding storm drain impacted and enclosed beaches for 5-10 days after a storm.”
Heal the Bay urges beachgoers to check the latest water quality grades for more than 400 beaches statewide, based on the latest samples, each week at beachreportcard.org.
The full UCLA-Heal the Bay report can be found here.