Stormwater—rain and snowmelt that runs off streets, rooftops, and other hard surfaces—can carry pollution such as bacteria, road salt, oil, trash, pesticides, fertilizers, and pet waste into our waters.

In some communities, heavy rains can overwhelm combined sewer systems, where stormwater and sewage share the same pipes. When these systems overflow, they can release untreated sewage into Casco Bay. Not all underground systems are combined, and many storm drains carry stormwater only—but even these discharges can deliver significant pollution.

While many municipalities are working to reduce combined sewer overflows and better manage stormwater, pollution from runoff remains a serious threat to marine life and public health. By documenting stormwater-related issues, Water Reporters help us understand where problems persist and advocate for cleaner water.