The grates cover what are known as catch basins, which are designed to collect stormwater as part of the storm sewer system. The storm sewer system is separate from the sanitary sewer system connected to your household plumbing and the stormwater is not treated prior to being discharged into a nearby wetland, stream, Farmington River, or Connecticut River. Therefore, it is important not to dump chemicals, fertilizers, pesticides, used motor oil, trash, grass clippings, or leaves into catch basin grates.
One gallon of used motor oil poured down a storm drain can create a four acre oil slick; contaminate up to one million gallons of water; and spread as far as 100 miles downstream from where the storm drain discharges into the nearest river or stream. This oil coats vegetation and wildlife, causing illness and death.