A new report from non-profit organization Save the Harbor/Save the Bay indicates that some progress is being made to improve water quality at Dorchester’s three beaches as public agencies work to repair pipes and other infrastructure that can lead to pollution. The report is based on data collected during the 2016 beach season from 15 public beaches from Nahant to Quincy.

Viewed over a six-year period, Dorchester’s Tenean Beach remained at the bottom of the list, with an average score of 81 percent in primary beach safety. Malibu Beach was slightly better, with an 89 percent average and Savin Hill posted a 94 percent average.

In 2016, however, the beaches scored 92 percent, 97 percent, and 100 percent, respectively— an improvement that experts say was driven higher by last year’s lower-than-normal rainfall.

“It’s always interesting to look at annual numbers,” said Bruce Berman of Save the Harbor/Save the Bay. “But it’s more important to look at the last few years, in this case the last six years. It gives you a more complete picture.”

Berman said that while Dorchester’s beaches have traditionally tested poorly, there have been recent improvements, likely the result of infrastructural repairs.

“Dorchester should be proud of their beaches,” he said. “That said, we still have more work to do, especially at Tenean.”

From Memorial Day to Labor Day, beach water is tested for the bacteria Enterococcus. Testers take a small water sample from the beach, place it in a Petri dish, and count the number of Enterococcus colonies that grow over a 24-hour period. In Dorchester, Savin Hill Beach is tested weekly, while Malibu and Tenean are tested daily. Although the standard is different for daily and weekly testing, all beaches are measured on a pass-fail basis, Berman said.

Savin Hill Beach is nearly always “terrific,” he said, while Malibu is mid-range and more negatively affected by rain. Tenean consistently has issues.

John Sullivan, chief engineer at the Boston Water and Sewer Commission (BWSC), said that Savin Hill and Malibu are largely clean because there is little risk of sewage contamination.

“At Savin Hill Beach, there is an emergency overflow that can be dumped there,” he said, “but it’s only during the hurricane-type events—and you shouldn’t be swimming during a hurricane. We don’t have any sewer pipes [at Malibu],” he noted, saying that the beach could be contaminated by a storm drain near the Savin Hill Yacht Club, although illicit connections in that area have been addressed already.

While Tenean remains at the bottom of the list in terms of water safety, it has seen recent improvements.

The efforts of Save the Harbor/Save the Bay, in partnership with BWSC and the Massachusetts Water Resources Authority (MWRA), appears to have increased water quality.

Sullivan said that recent repairs show a correlation with a reduction in contamination at Tenean. In May 2016, BWSC spent around $77,000 repairing a sewer with a leaky joint near Pine Neck Creek.

“We noticed that right after that, the amount of contamination on the beach seemed to drop,” Sullivan said. “Of course, it didn’t rain that much.”

Last year, Massachusetts was in the midst of the worst drought the state had seen in more than a decade. Rain is a chief factor in water quality: the more rainfall, the more likely runoff is to enter beach water and increase contamination levels.

“You cannot assume anything,” Sullivan said. “You’ve got to check it, and check it, and check it.”

Since 2011, Sullivan said his team has fixed 22 illicit connections between the sewer and the drain system near Victory Road, just north of Tenean Beach. Sullivan estimates that they have removed around 1,700 gallons of sewage that was entering storm drains daily. He also cited a broken sewer on Charles Street near Fields Corner, calling it a “significant leak” whose fix he believes also contributed to a “substantial reduction in the amount of pollution” at Tenean.

Sullivan said the nature of determining water contaminant sources is imprecise. Because the water and sewer system’s infrastructure is completely underground, it is difficult to know when something breaks; “sometimes,” he said, “it just decides to.”

MWRA spokeswoman Ria Convery applauded Sullivan and Berman’s work.

“It’s been a great partnership,” she said. “They’ve been really helpful with their criticisms and with their support.”

State Rep. Dan Hunt, who represents the 13th Suffolk District, which includes most of Dorchester, has long advocated for local infrastructure improvements. Prior to his election in 2014, Hunt worked for the state’s Department of Conservation and Recreation. In office, he has pushed for a project to improve drainage and elevations on William T. Morrissey Boulevard between the John J. Beades drawbridge and UMass Boston.

“All of those street drains are picking up all the water and all the bird droppings and everything else and draining them all to the same spot,” Hunt said. “Instead of draining directly, can we get a catch basin that holds the water for a few days so that it can be treated?”

Hunt pointed out that the current system of testing beach water does not necessarily reflect its safety, since warnings about water quality are put out the day after samples are collected.

“The days that you get high bacteria counts there, it doesn’t really reflect the actual situation, and it’s actually much better than the numbers say as far as swimability goes,” Hunt said. “If you had an instant test, which doesn’t exist, then it would be fine to swim.”

Last Saturday, Save the Harbor/Save the Bay awarded more than $55,000 in Better Beaches Program Grants to support free events and activities on regional beaches. According to a statement from the organization, the Friends of Savin Hill Shores received $2,000 for the Dorchester Beach Festival, and the Port Norfolk Civic Association received $2,500 for Tenean Beach Day.

Berman and his colleagues at Save the Harbor/Save the Bay are eager to help communities with low-scoring beaches this summer. He said the organization has scheduled two cleaning days at Victory Park—one in June and one in the fall— as they try to determine whether dog waste could play a significant factor in pollution at Tenean Beach.

“It’s a question of will, and I think we have the will,” Berman said. “And then it’s a question of whether we have the resources.”

For his part, Sullivan, plans to monitor water quality, find broken connections, and resolve any issues are simply a matter of course.

“We’re going to be watching that extremely closely, and if we see any uptick, we’re going to be back in your pipes,” he said. “We’re the only people in the world that are happy to find the problem and want to spend the money to fix it.”