As multiple heat waves have swept across our region, you may have noticed that Upper Mystic Lake’s Shannon Beach, the only free public freshwater beach in the Mystic River watershed, has been closed nearly all summer. In fact, it is one among many beaches across the state that have closed due to concerns around the level of harmful bacteria in the water. Ahead of July 4th weekend, over 30 beaches were closed to swimming, including Shannon Beach, which has remained closed since early June.

Frequent and long-term beach closures reveal a hard truth - the way we are managing our public beaches is broken. Beaches are important resources, particularly during the hottest days of the summer when we need public places to stay cool. This summer, MyRWA is working to better understand why these closures are so common and how we can work to make sure the beaches stay open.

How Do I See if the Beach is Closed?

Shannon Beach is managed by the Massachusetts Department of Conservation and Recreation (Mass DCR). You can check the DCR Park Alerts and the Massachusetts Department of Public Health Interactive Beach Water Quality Dashboard to see if the beach is closed. On days when the beach is closed, DCR will hang red flags on the lifeguard chairs and lifeguards will not be on duty.

How Do We Decide When to Close the Beach?

As of 7/9/2024, bacterial sampling has led to a geometric mean value above the threshold since the geometric mean was first calculated in early June. Credit: Mass DPH Interactive Beach Water Quality Dashboard

Beaches can be closed for a variety of reasons, including hazardous weather conditions, chemicals, and toxic algae blooms. However, the primary reason for beach closures at Shannon Beach is “bacterial exceedance” – AKA too much harmful bacteria in the water. Mass DCR regularly tests the water at Shannon Beach to determine the level of bacteria. When the average level of bacteria from the past five consecutive samples exceeds their threshold, the beach is closed. You can view the testing data on the Dashboard. Because swimming requires a different threshold than boating, you might find that Shannon Beach is closed even when Upper Mystic Lake is deemed safe on MyRWA’s Daily Boating Advisory.

Bacteria can get into the water in a variety of ways. Water flows into the Mystic Lakes from the Aberjona River and through stormwater pipes and rainwater runoff. Though there are no combined sewer overflows upstream from the beach, bacteria can still get into the water through illicit connections, overflows of sanitary sewer systems, or unintended cross-contamination between sewer and stormwater pipes deep underground. In addition, when it rains, anything on the streets, roofs, and other impervious surfaces gets flushed directly into rivers and streams through storm drains, including animal waste and other pollutants, which can increase the level of bacteria in the water. In general, the Mystic River Watershed Association recommends not swimming or boating anywhere on the Mystic for 48 hours after heavy rain.

What is MyRWA Doing About Shannon Beach Closures?

MyRWA is conducting expanded sampling at the Mystic Lakes and upstream on the Aberjona River to better understand water quality issues at the beach and possible sources. We will share this data with DCR and continue to review best practices for protecting public health–that does not require the beach to be closed most of the summer.

In the meantime, you should check our Daily Boating Advisory to see if it’s safe to boat on the water, wear a life jacket when boating, and please practice swim safety, especially if you choose to swim or float in open water. Helpful tips below!