Below are frequently asked and important questions. See the Stormwater tab for general questions on stormwater. See Stormwater Management at the City to see what we are doing in Mountlake Terrace to protect surface water. See the Stormwater Rates tab to learn more about stormwater rates on properties in Mountlake Terrace.
What is stormwater?
Stormwater is rain and snow melt that runs off of impervious surfaces such as rooftops, paved streets, highways, and parking lots. Stormwater runoff collects pollutants and transports pollutants to surface water bodies such as Lake Ballinger and Lake Washington. Cities like Mountlake Terrace that have high level of development produce more stormwater runoff unless Low Impact Development practices are implemented.
Is stormwater treated?
In Mountlake Terrace, stormwater is not treated when it goes into a storm drain. The stormwater system is not connected to the sanitary sewer system nor is it treated in any way to remove pollutants before being released into the environment. Therefore, the quality of stormwater going into the drainage system is what determines the level of pollution in surface water.
What are stormwater pollutants and what do they do?
Any substance that is not naturally in rain can be considered a pollutant. Typical stormwater pollutants include:
Sediment in excess turns the water cloudy, making it less suitable for recreation, aquatic 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 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, 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.
Oils and greases 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 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 affect receiving waters, including phenols, glycol ethers, esters, nitrosamines, and other nitrogen compounds. Common sources of these compounds include wood preservatives, antifreeze, and cleaners.
Bacteria and other pathogens, such as fecal coliform bacteria, 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 lead to closures of shellfish harvesting areas and public swimming beaches.
pH is a measure of water and can be neutral, very high (basic), or very low (acidic). High or low pH in water can release metals or other contaminants into the environment and cause biological problems for aquatic organisms and fish. Several sources can contribute to change of pH in runoff, including acidic chemicals, cement used in concrete products and concrete pavement, and chemical cleaners.
Information from the Port of Seattle.
What is the primary source of pollutants?
The primary cause of pollution in stormwater runoff is individual human activity, not industrial dumping. Success in reducing environmental pollution depends upon everyone’s participation.
What can I do to improve stormwater in Mountlake Terrace?
Check out our page on how to get involved here.
What do I do if I see something other than stormwater going into a drain or stream?
To report a pollutant spill to the stormwater system call the Public Works Department at 425-670-8264 between 8 a.m. and 5 p.m. weekdays. Call 911 after hours, on weekends, or during holidays.
What is NDPES?
The National Pollutant Discharge Elimination System (NPDES) is a program that controls water pollution by regulating the discharge of pollutants through discharge permits. The federal law that defines it is the Clean Water Act, and in Washington State the Washington Department of Ecology issues permits. The City of Mountlake Terrace has a Phase II NDPES Municipal Stormwater Permit.
The permit requires the City to create a Stormwater Management Program (SWMP) which includes public outreach and education, public engagement and participation, illicit discharge detection and elimination, control of runoff from new development, redevelopment, and construction sites, and municipal operation and maintenance program.
What does the operation and maintenance program look like?
The stormwater division regularly screens and cleans stormwater catch basins to keep pollutants out of surface waters. The division also maintains and cleans stormwater facilities which prevent flooding and improve surface water quality. When a spill occurs in Mountlake Terrace the division responds.
What requirements exist for new development, redevelopment, and construction sites?
To learn more about requirements see Ordinance 2729.
Where is the Stormwater Management Plan?
Why are there stormwater fees in Mountlake Terrace?
The City’s stormwater division works to control flooding, protect water quality, improve creek and lake habitat, and comply with state and federal requirements for clean water. Actions undertaken include maintaining and cleaning stormwater facilities to avoid flooding, public education and outreach, responding to pollutant spills, inspections, reviewing stormwater plans for new development, and managing municipal operations to protect stormwater. To accomplish these tasks, revenue is required. In 2019, the MLT stormwater rate study reviewed stormwater division costs to deliver services and capital improvements against the revenue received from stormwater service fees. The stormwater rate study report provides a detailed explanation of that analysis.
Why did rates increase?
The stormwater rates were increased in order to balance the budget and perform the desired level of service for Mountlake Terrace.
How are rates calculated?
Please see below to see how stormwater rates are calculated in Mountlake Terrace.