Public Works

Rainwater that flows across the land is called stormwater.  In vegetated areas such as forests, fields and wetlands, rainwater seeps into the ground. However, when rain falls on paved and other hard surfaces, it runs off and is conveyed by pipes and infrastructure directly to wetlands, streams, creeks and eventually to the Laguna de Santa Rosa.  Stormwater runoff is generated by runoff from land and impervious areas such as paved streets, parking lots, and building rooftops during rainfall events that often contain pollutants in quantities that could adversely affect water quality.

Urban Runoff is rain and any other water that passes through and out of developed areas (streets, parking lots, rooftops, etc.) into the storm drain system and eventually to creeks and other waters.

Any substance that is not naturally in rain can be considered a pollutant. Potential pollutants can include:

• Sediment: Bare soil/ground, construction, dirt from vehicles are all sources of sediment that can turn water cloudy making it less suitable for aquatic life and plants. Sediment also carries pollutants such as chemicals, oils and metals as well.
• Nutrients: Excessive nutrients such as phosphorus and nitrogen can over stimulate the growth of algae and other aquatic plants, affecting water quality, creating unpleasant odors and lowered dissolved oxygen levels from plant decay. Some forms of algae are also toxic to fish and other aquatic organisms, pets, and humans. Fertilizers, animal wastes, detergents, road de-icing salts, automobile emissions, and organic matter are all contributors to excessive nutrient levels in stormwater runoff.
• pH: Waters with very low (acidic) or very high (basic) pH are corrosive and can cause biological problems for aquatic organisms and fish. Cement used in concrete products and concrete pavements, chemical cleaners and acidic chemicals all can tribute to pH.
• Metals: Many metals, including lead, copper, and zinc, are commonly found in urban runoff. Dissolved metals, in very low concentrations, can be toxic to aquatic organisms and interfere with reproduction. Metals can adhere to and contaminate sediments in creeks and streams. Pesticides and paints, vehicle use and other materials contribute to metals in stormwater.
• Oils and Grease: Oil and grease can be toxic to aquatic organisms at relatively low concentrations. Oil and grease from vehicles, streets and roadways, parking lots, gas stations and other equipment/machinery contribute to oils and grease in storm water.
• Bacteria and other pathogens: Fecal coliform bacteria in water may indicate the presence of pathogenic (disease-causing) bacteria and viruses. Pet and other animal wastes, failing septic systems, livestock waste in agricultural areas and on hobby farms and fertilizers can all contribute fecal coliform bacteria.
• Toxic Organic Compounds: Toxic compounds such as pesticides, cleaners, and paints are particularly dangerous in the aquatic environment and can be lethal to aquatic organisms. Excessive application of insecticides, herbicides, fungicides, and rodenticides, shortly before a storm, or application on impervious surfaces can result in the pesticide being carried to receiving waters. Cleaners, even those marked non-toxic and biodegradable, are toxic to aquatic organisms in very small quantities. Many other toxic organic compounds can also affect receiving waters, including phenols, glycol ethers, esters, nitrosamines, and other nitrogen compounds. Common sources of these compounds include wood preservatives, antifreeze, and cleansers.

No, stormwater flows do not receive treatment prior to entering the storm drain system and local creeks.

The storm drain system was built to collect and transport rain to prevent flooding in urban areas. Anything that flows or is discharged into the storm drain system goes directly into local creeks without any treatment. The sanitary sewer system collects and transports sanitary wastes from homes and businesses (sinks, baths, and toilets) plumbing systems to the City of Santa Rosa’s Laguna wastewater treatment plant, where the wastewater is treated and reused.