A rash of beach closures south of Boston in the past two months can be attributed to dry summer weather followed by heavy rains, but, overall, beaches on the South Shore and along the south coast are cleaner than they’ve ever been, officials say.
Last week, all four sections of Wollaston Beach in Quincy were closed after testing showed elevated levels of bacteria. Beaches are closed if they have bacteria readings higher than 104 colony-forming units per 100 milliliters of water. The results of tests conducted last Sunday showed the Channing Street beach was more than six times the limit, Milton Street was 3 times over the limit, Rice Road more than four times, and Sachem Street was more than 12 times the limit.
Although all four Wollaston beaches had results lower than the threshold on Monday and Tuesday, they remained closed to swimming as a precautionary measure until further testing was done.
Two weeks ago, seven beaches in Quincy and two in Hingham were closed to swimming due to bacterial contamination. Mound Beach in Quincy was 11 times over the limit considered safe, and Merrymount Beach was eight times over the limit. Broady (Baker) and Germantown beaches were also over the limit. Sections of Wollaston Beach were also closed as a precaution, even though the water was within acceptable limits.
In Hingham, Kimball Beach tested at 20 times the limit, and Wompatuck Beach was almost three times the limit.
In June, 10 beaches along the South Shore were closed because of high bacteria counts following heavy rain.
Some area beaches, like ones in Marion, Mattapoisett, and Wareham, tested higher than usual after summer storms, but were well below the unsafe threshold, and levels fell to normal following the storm. In Wareham, Briarwood Beach was closed after exceeding the safety zone in late June, but by the following week levels met safety standards and the beach was reopened.
High levels of contaminants can often be traced to heavy rainfall overwhelming older drainage and sewer systems and dumping that water directly into the ocean, said Gary Briere, assistant director for parks for the state Department of Conservation and Recreation. Levels can also spike when beach debris, such as dog and seagull feces, wash into the water, as well as from people dumping sewage from boats, and other activities.
Officials are testing some beaches more than others this year, with some receiving daily tests and ones that rarely have a problem checked monthly, but overall the level remains consistent, Department of Conservation and Recreation spokeswoman S.J. Port said. Last year, the state tested 15,752 samples from salt- and freshwater beaches, compared with 15,409 in 2010 and 15,803 in 2009, according to state Bureau of Environmental Health reports.
This summer’s rain has been fairly typical, with some areas getting soaked and others staying dry, said Alan Dunham, a meteorologist with the National Weather Service in Taunton. With the season’s pattern of showers and thunderstorms, he said, “you can get a very heavy amount of rain in a short amount of time. Also, thunderstorms are hit or miss. Some get a deluge; others get nothing.”
The opening of a $225 million, 2.1-mile-long sewage holding tank under Day Boulevard in South Boston last summer virtually eliminated closures of nearby beaches. The system temporarily stores up to 19 million gallons of waste water that would otherwise overwhelm the sewer system during heavy rainstorms, sending untreated sewage into the harbor off South Boston and Dorchester. The dirty water collected in the underground tank is pumped to the Deer Island treatment plant once storms pass.
The holding tank, the last part of the nearly $5 billion Boston Harbor cleanup, is also helping to keep beaches in other communities cleaner.
“Compared to 20 or even five years ago, harbor beaches are so much cleaner than before. We’ve got some of the cleanest urban beaches in America,” Briere said.
But communities that are not in the Massachusetts Water Resources Authority system can’t easily duplicate the tunnel system. On the South Shore, Nantasket Beach in Hull and Wollaston Beach in Quincy are covered by the state Department of Conservation and Recreation. Other beaches are under the control of communities that have limited resources to deal with drainage problems.
High contaminant levels at beaches in Scituate and Duxbury this summer are “largely related to storm water,” Save the Harbor/Save the Bay spokesman Bruce Berman said. “When we have these torrential rains,’’ he said, the beaches are hit with storm water carrying all the debris “that’s built up since the previous rain.”
On the South Shore, 75 saltwater beaches are tested by local health officials for enterococci, an indicator of contamination found in fecal matter that can cause upset stomachs, diarrhea, rashes, or earaches. High levels of enterococci indicate the water may also contain other disease-causing microbes that are more difficult to detect, the Woods Hole Oceanographic Institution’s website states.
Waiting a day or so after a storm to go swimming typically allows the contaminants to wash out to sea, leaving the water safe again for swimming, state parks official Briere said.
“As the tides come and go and flush things out, the conditions 12 hours later are really dramatically different from what they are right after that rain event,” he said.Sarah Coffey can be reached at firstname.lastname@example.org.