While the upper and main beaches at Hopkinton State Park remain closed due to high bacteria counts, the water quality at Sandy Beach remains safe for swimming and boating, providing an oasis for Hopkinton residents during the weekend’s scorching temperatures.

On Friday, Health Department director Shaun McAuliffe released water quality reports for Sandy Beach. Samples were taken by Health Department staff to analyze for E. coli, a bacteria that can cause diarrhea, nausea, vomiting and stomach cramping if ingested, according to the Mayo Clinic.

“The water quality has been good at Sandy Beach all year,” McAuliffe said in an interview with the Independent Saturday morning, noting that it is typically tested every Wednesday.

The reportable concentration to the Massachusetts Department of Public Health is 235 colonies per 100 milliliters, he explained. Three samples are taken at different sections of the water to assure there are no anomalies. The results at the center and right sides of the beach were 8.6 and 9.7, respectively, far below the reportable level. The left side of the beach had a higher colony rate of 47.1, still well under the reportable level.

“Typically the right side of the beach has the highest concentration because it is close to the outflow pipe for the storm drain system,” he said.

McAuliffe credited the combined efforts of the Lake Maspenock Preservation Association, the Health Department, the Department of Public Works and the Parks & Recreation Department for educating the public about what they can do to maintain the lake’s high water quality.

“E. coli is an indicator of fecal contamination,” he said. “The lake association has been doing a good job educating people about the importance of picking up after themselves and their dogs and not leaving dirty diapers behind in the water, as well as fertilizer use. We also monitor a lot of the inlet channels for cyanobacteria [previously known as blue-green algae].”

A limnologist, a scientist who specifically studies lakes and other freshwater systems, lives on Lake Maspenock and keeps in contact with McAuliffe, he said.

Bacteria levels continue to remain a concern at the upper and lower beaches at Hopkinton State Park during the hottest time of the year, he added.

“This has been going on for about a month now,” McAuliffe said. “This can be caused by geese droppings, dirty diapers in the water, and dog waste. It’s kind of like the Wild West there.”