40 percent of Rhode Island beaches sampled tested positive for fecal bacteria at least once in 2018 according to a report released Tuesday by advocacy group Environment America.

“There are many of these sites where 20, 35 percent of the time that they sampled for fecal bacteria it exceeded the EPA’s conservative benchmark for keeping the public safe,” said John Rumpler, co-author of the report and Clean Water Program Director Environment America.

The report relied on testing data for Enterrococcus or Escherichia coli downloaded from the National Water Quality Monitoring Council’s Water Quality Data portal.

One major source of potential contamination is overflow from wastewater treatment plans during storms. Beach closures have stabilized since the Narragansett Bay Commission improved its sewer overflow infrastructure in 2009, according to the Rhode Island Department of Health. But Rumpler, a Rhode Island native, said the report shows that more prevention is needed.

“Absolutely preventing sewer overflows is a critical step to reducing the amount of unhealthy bacteria at our beaches and in Narragansett Bay,” Rumpler said. “We also need to be doing work to prevent storm-water runoff pollution as well.”

Rumpler pointed to rain barrels, rooftop gardens, urban greenspace, and vegetative buffers as promising ways to reduce rain from washing pollutants and fertilizer into waterways.

Rumpler added, impact of storm-water runoff on coastal regions is growing as climate change tends to bring storms with heavier rainfall, increasing the risk that the runoff will overwhelm wastewater management systems.

“To the extent that climate change is bringing more intense heavy rainfall during storm, we’ll see more of this runoff pollution and more of these sewer overflows if we don’t take steps to prevent them,” Rumpler said.