Bacteria

The warm sand and cold water of Lake Champlain’s beaches are quintessential cures for the dog days of summer. As air and lake temperatures rise, more people flock to the lake for a swim. Imagine the disappointment if they reached the water only to find a sign warning that the beach is closed due to health risks.

In some places, old and leaking septic systems may be nearby, leading to beach closures. At other locations, extensive urban development may mean stormwater runoff carries bacteria to a beach. Warm, shallow areas of the lake are more susceptible to high bacteria counts than cold, deep waters. Areas with little or no development around them are unlikely to have problems with contamination.  Potential sources will differ with every beach, so it would be inappropriate to generalize about beach health for Lake Champlain as a whole.

New York, Vermont and Quebec have different standards for determining when bacterial levels are high enough to close beaches and even for how frequently beaches should be tested. However, one generalization can be made: bacterial levels tend to be highest at any beach following a rainstorm, particularly in urbanized areas. 

Major storms can cause overflows at wastewater treatment facilities, further contributing to bacterial loads. Urbanized areas use wastewater treatment plants more than rural areas. Even without such overflows, sources of bacteria accumulate on land between storms and move to a water body with stormwater runoff. Water moves greater distances over paved land, thus having more opportunity to pick-up bacteria as compared to grasses, fields or forests, where the water can seep into the ground. 

In most parts of Lake Champlain on most days, swimming is healthy, enjoyable recreation. In urbanized areas following a rainstorm, swimming might best be avoided for a day or two.