Rain water that flows across the land is called stormwater runoff. In vegetated areas such as forests, fields and wetlands, rain water seeps into the ground. However, when rain falls on paved and other hard surfaces it runs off and is conveyed by pipes and ditches directly to wetlands, streams, rivers, and Puget Sound.
Stormwater runoff collects pollutants when it hits the ground, comes into contact with pollutants, and transports the pollutants to a waterbody. Many of our water pollution problems are due in large part to pollutants that are washed off the land by storms. When small amounts of pollutants from many sources are combined, they can cause big water quality problems.
Stormwater runoff increases the volume of water in streams because pavement surrounding the stream is impervious and does not allow rainwater to infiltrate into the soil. As development occurs, an increase in stormwater runoff volume is generated. Increased stormwater causes flooding, scours stream and river substrates, and impacts habitat. Since less water infiltrates into the ground, there is less water available for stream base flows.
Any substance that is not naturally in rain can be considered a pollutant; typical stormwater pollutants include:Sediment
: Excess sediment turns the water cloudy, making it less suitable for recreation, fish life, and plant growth. When the sediment settles in the receiving water, it can smother trout and salmon eggs, destroy insect habitat (a food source for fish), and cover prime spawning areas. Many other pollutants (oils, metals, toxic chemicals, bacteria) attach to the sediment. This pollutant-laden sediment can settle and contaminate the receiving water body. Exposed earth, construction, and dirt from equipment, vehicles and parking lots are sources for sediment. Nutrients
: Nutrients such as phosphorus and nitrogen are needed by plants to grow, but high levels can be harmful to water quality. Excess nutrient levels can over-stimulate the growth of algae and other aquatic plants, resulting in unpleasant odors, unsightly surface scums, and lowered dissolved oxygen levels from plant decay. Lower dissolved oxygen levels kill fish. Some forms of algae are also toxic to fish and other aquatic organisms, pets, and humans. Fertilizers, animal wastes, detergents, road deicing salts, automobile emissions, and organic matter are all contributors to excessive nutrient levels in stormwater runoff. Metals
: Many metals, including lead, copper, zinc and cadmium, are commonly found in urban runoff. Dissolved metals, in very low concentrations, can be toxic to aquatic organisms, interfere with their ability to respond to predators, and interfere with reproduction. Metals can adhere to and contaminate sediments in water bodies. Sources of metals in stormwater include vehicle use (copper from brakes and zinc from tires), galvanized metal (zinc from roofs, fences), pesticides, and paints.
Read Zinc: guidance for maintenance, construction and project planning
here.Oils and Greases
: Oil and grease are known to be toxic to aquatic organisms at relatively low concentrations; they can coat fish gills and prevent oxygen from entering the water. Sources of oils and grease include vehicle use, streets and highways, parking lots, fueling areas, and equipment and machinery storage areas. Chemical and Hazardous Substances
: 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. Bacteria and other pathogens
: Fecal coliform bacteria in water may indicate the presence of pathogenic (disease-causing) bacteria and viruses. Pet wastes, wildlife wastes, leaking dumpsters, and improperly connected sanitation systems can all contribute fecal coliform bacteria. Bacteria contamination can cause human illness, limit recreational use of a water body, and can lead to closures of shellfish harvesting areas and public swimming beaches. pH
: Waters with very high (basic) or very low (acidic) pH are corrosive to metal surfaces and can cause biological problems for aquatic organisms and fish. There are several sources that can contribute to change of pH in runoff; these include acidic chemicals, cement used in concrete products and concrete pavement, and chemical cleaners.
The Port of Seattle formed a Marine Stormwater Utility under the authority of several sections of the RCW and other statutes which authorize port districts to provide services, facilities, systems, and programs for surface water and stormwater management and pollution control. Our utility serves all Port-owned land within King County.
Prior to January 2016, drainage fees were collected by the Port and paid to the City of Seattle Public Utilities (SPU). These fees were directed at maintaining and managing stormwater programs throughout the City, not specific to Port properties. The formation of the Port's utility allows increased investments in managing and maintaining stormwater systems on Port properties.
For more information you may view Port of Seattle Commission Resolution No. 3696