According to the California State Water Resources Control Board, storm water pollution is the number one cause of water pollution in California. More than 85 billion gallons of untreated, contaminated water flow into the Bay area each year from storm drains alone. For example, leaves soak up herbicides and other contaminants, and paint is toxic to aquatic life, so these seemingly safe materials can be potentially quite harmful. Don't sweep them into streets or gutters. Many cities and landfills have yard waste composting programs and yard waste recycling programs.
Some programs even provide curbside pickup.
When using water-based paints, wipe the excess onto scrap material, then rinse the brushes into a sink which flows to the sanitary sewer. If completely dried out, empty water-based paint cans, spent brushes and rags may be disposed of as regular trash. It is a good idea to leave the lids off paint cans so refuse collectors can see they are empty. Conversely, oil-based paints should never be poured into the sink. Thinners and solvents used to mix or clean up oil-based paint should be filtered and reused.