SWAMPSCOTT — Water quality grades are in for urban beaches in Greater Boston and, for the most part, the ocean is clear.
More than half of the 15 beaches where the nonprofit group Save the Harbor/Save the Bay conducted testing last year posted perfect water quality scores, meaning all samples examined for bacteria were deemed safe for swimming under state public health standards.
At the bottom of the rankings were King’s Beach on the Lynn-Swampscott line and Tenean Beach in Dorchester, where bacteria levels were considered unsafe during about a quarter of last year’s swimming season.
The water quality findings for beaches from Hull to parts of the North Shore were made public Sunday in an annual report from Save the Harbor/Save the Bay.
Bruce Berman, the group’s director of strategy and communications, said the high marks for many beaches are significant given the record 61 inches of rain that fell in Massachusetts last year. Without the proper infrastructure, stormwater unleashed during storms can pollute beach water, he said.
“The improvements that we made really work in wet weather,” Berman said Saturday.
Two beaches in South Boston, Nantasket Beach in Hull, Nahant Beach in Nahant, Winthrop Beach in Winthrop, Short Beach in Revere, and Savin Hill Beach in Dorchester aced their water quality tests last year, the report said.
Weekly testing began on May 24, 2018, and daily testing at King’s Beach and four other beaches in East Boston, Dorchester, and Quincy began on June 7, 2018. Testing concluded on Sept. 3, 2018.
Alerts about high bacteria levels, Berman said, are based on tests of water samples collected a day ahead of time. He urged swimmers to use common sense when deciding whether to go in the water.
Save the Harbor/Save the Bay began its water quality testing program at urban beaches in 2011, Berman said, the same year the Boston Harbor cleanup project marked a major milestone with the opening of a massive sewage holding tank in South Boston.
The 2.1-mile tank under Day Boulevard is credited with keeping dirty water out of the harbor when it rains. The federal court case that led to the $5 billion Boston Harbor cleanup ended in 2016 after than three decades.
M Street Beach in South Boston holds the distinction of having an average water quality safety rating of 100 percent over six years, the report said.
King’s Beach and Tenean Beach have consistently ranked at the bottom of the list.
Last summer, King’s Beach was safe for swimming 75 percent of the time and Tenean Beach was safe for swimming 78 percent of the time, the report said.
Going back to 2013, Tenean Beach had the lowest average safety levels, according to the report, and King’s Beach was second to last.
Swimming in waters with high bacteria levels puts people at risk of developing rashes, eye infections, and gastrointestinal illnesses, Berman said.
At Tenean Beach, high bacteria levels are believed to be caused by sewage systems that were improperly connected to stormwater pipes, he said. The Boston Water and Sewer Commission has been working to identify problem connections, he said, and reroute waste.
Dolores Randolph, a commission spokeswoman, said Tenean Beach has been a challenge. Problem spots have been identified and fixed, she said, only for testing to reveal other areas that requires attention.
The commission, she said, has begun repairs on a problem spot that was recently identified and feels optimistic about the work.
At King’s Beach, the bacteria levels have been linked to problems with stormwater pipes in Lynn and sewer systems in Swampscott, Berman said.
In 2015, Swampscott agreed to pay a $65,000 civil penalty after the US Environmental Protection Agency accused the town of discharging pollutants into its stormwater drainage system.
Since then, the town has spent $4 million to enclose clay pipes in protective sleeves to prevent leaks, said Town Administrator Sean R. Fitzgerald.
Fixing the problem entirely, however, will require financial assistance from state and federal authorities, he said.
“We can’t afford to do this all on the local real estate tax base,” Fitzgerald said.
In Lynn, city officials are trying to identify broken pipes and spots where sewage systems were incorrectly linked to stormwater pipes, Berman said.
Lynn and Swampscott are eligible for state funds from a $20 million environmental bond bill that was authorized two years ago, though the money has yet to be appropriated, Berman said.
The state Department of Conservation and Recreation, which oversees the beaches, is committed to their protection and improvement, a spokeswoman said.
Lynn Mayor Thomas M. McGee didn’t respond Saturday to requests for comment.
Sean Regan, 36, of Swampscott, brought his 2-year-old daughter Annabelle to King’s Beach Saturday afternoon. He said he wasn’t surprised to hear the beach fared poorly on water quality tests, but believes the beach is relatively clean compared to other bodies of water nationwide.
“It doesn’t concern me all that much,” Regan said. “We probably wouldn’t choose this beach to go swimming in, but at the same time I don’t think it’s toxic.”
Shanel Anderson, 35, said she wasn’t aware that King’s Beach sits low in the rankings compared to nearby beaches. Officials need to do a better job of informing the public of bacteria levels, she said.
“We love the beach. This is pretty much our standard activity to do,” said Anderson, who visited the beach with her sons, Solomon, 8, and Kingston, 4. “I never think twice about it. It’s something that I’m definitely going to think about from now on.”
Robert Tucker, president of the nonprofit organization Friends of Lynn and Nahant Beach, said officials in Lynn and Swampscott haven’t done enough to improve water quality at King’s Beach. “It’s just not getting resolved the way it should be resolved,” he said.