Heavy rains can wash contaminants into drinking, recreational, and irrigation waters, potentially leading to human illnesses. Harmful contaminants include human and animal waste, industrial chemicals, oil and fuel, and pesticides and fertilizers. Heavy rains can also result in overflows of combined sewer systems, which are designed to treat both stormwater and wastewater at the same time. During heavy rains, there may not be enough capacity in the system, leading to the discharge of untreated or partially treated wastewater. Flooding can make all of these problems even worse.
Vermont averages over 500 reported cases of waterborne or foodborne illnesses each year. Reported illnesses are more likely during the warmest months and following heavy rains. Beach closures are common following heavy rains, as sewage or animal waste can wash into surface waters and result in unsafe E. coli bacteria levels for up to 48 hours following a heavy rainfall event. During Tropical Storm Irene, 30 public water systems experienced treatment system failures, many private wells were contaminated by flood waters, and over $10 million in damage occurred to crops and farmlands affected by flooding.
Days with very heavy rain (at least 1 inch or more) occur almost twice as often today as they did 50 years ago, and are expected to become even more frequent in the future. More frequent heavy rains combined with warmer water conditions are likely to increase the risk for waterborne and foodborne illnesses in the future.
- What individuals and communities should test for in private and public water supplies
- Why private and public water supplies should be tested
- How individuals and communities can monitor and maintain safe recreational waters
- How and why beaches are closed due to E. coli and other health concerns—Lake Champlain Basin Program
- View recent combined sewer overflows and other sewage incidents—Vermont Department of Environmental Conservation