Frequently Asked Questions (FAQ)

Stormwater means the water produced from rain or melting snow, which runs off, soaks into the ground, or is dissipated through evapotranspiration. Stormwater that runs off or soaks into the ground ultimately becomes surface water or groundwater.

On its way to streams, lakes and other water bodies, stormwater runoff can pick up and carry many substances that pollute water. This is known as non-point source pollution.

Some pollutants like pesticides, fertilizers, oil and soap, are harmful in any quantity. Other pollutants like pet waste, grass clippings, leaves and sediment from construction, bare soil, or agricultural land can harm creeks, rivers and lakes in sufficient quantities.

In addition to rain and snowmelt, various human activities like driveway pressure washing, car washing, and malfunctioning septic tanks can also put water onto the land surface. Here, it can also create runoff that carries pollutants to creeks, rivers, and lakes.

Polluted runoff generally happens anywhere people use or alter the land. For example, in developed areas, none of the water that falls on hard surfaces like roofs, driveways, parking lots or roads can seep into the ground. These impervious surfaces create large amounts of runoff that picks up pollutants. The runoff flows from gutters and storm drains to streams. Runoff not only pollutes but erodes streambanks. The mix of pollution and eroded dirt muddies the water and causes problems downstream.

Polluted stormwater runoff generally happens anywhere people use or alter the land. People going about their daily lives are the number one source of stormwater pollutants.

Most people are unaware of how they impact water quality. Some common examples include over fertilizing lawns, excessive pesticide use, not picking up pet waste, driving cars on roads, letting oil drip from vehicles and littering.

Developed areas in general, with their increased runoff, concentrated numbers of people and animals, construction and other activities, are a major contributor to non-point source pollution, as are agricultural activities. Other contributors include forest harvesting activities, roadways, and malfunctioning septic systems.

Polluted stormwater runoff is the number one cause of water pollution in Washington. In most cases in today, stormwater either does not receive any treatment before it enters our waterways or is inadequately treated.

Polluted water creates numerous costs to the public and to wildlife. As the saying goes, “we all live downstream.” Communities that use surface water for their drinking supply must pay much more to clean up polluted water than clean water.

Polluted water hurts the wildlife in creeks, streams, rivers and lakes. Dirt from erosion, also called sediment, covers up fish habitats. Fertilizers can cause too much algae to grow, which also hurts wildlife by using up the oxygen they need to survive. Soaps hurt fish gills and fish skin, and other chemicals damage plants and animals when they enter the water.

The quantity of stormwater is also a problem. When stormwater falls on hard surfaces like roads, roofs, driveways and parking lots, it cannot seep into the ground, creating more volumes of surface runoff.

As Sammamish grows and we build more rooftops, driveways, streets, and other hard or impervious surfaces, the land’s capacity to soak up and carry away excess water decreases. As a result, conditions that might result in a flood once every 100 years in an undeveloped area can cause flooding every four or five years after development has covered the land with impervious surfaces. The high volume of water also causes stream banks to erode and washes the wildlife that live there downstream.

“Best management practices” is a term used to describe different ways to keep pollutants out of runoff and to slow down high volumes of runoff.

Preventing pollution from entering water is much more affordable than cleaning polluted water! Educating residents about how to prevent pollution from entering waterways is one best management practice. City codes that require people and businesses involved in earth disturbing activities --like construction-- to take steps to prevent erosion are another way to prevent stormwater pollution. There are also laws about litter, cleaning up after pets, and dumping oil or other substances into storm drains.

Education and codes are just two best management practice examples. Some BMPs are constructed to protect a certain area. Some are designed to slow down stormwater, others help reduce the pollutants already in it – there are also BMPs that do both of these things.

Detention ponds and other structures are built to temporarily hold water so it drains away slowly. They fill up quickly after a rainstorm and allow solids like sediment and litter to settle at the pond bottom. Then, the water slowly drains. These facilities are one constructed BMP example. There are also acceptable and allowable discharges to the MS4.

A best management practice (BMP) is any schedule of activities, prohibition of practices, maintenance procedure, or structural and/or managerial practice that, when used singly or in combination, prevents or reduces the release of pollutants and other adverse impacts to surface water, stormwater and groundwater.

This is another term for polluted runoff and other sources of water pollution that do not flow from a single point. Stormwater sheet flowing from a parking lot is an example of nonpoint source pollution. The term “nonpoint source pollution” comes from the federal Clean Water Act of 1987. There, it is used as a catch-all for all kinds of water pollution that are not well-defined discharges (point sources) from wastewater plants or industries.

The federal Clean Water Act requires large and medium sized towns across the United States to take steps to reduce polluted stormwater runoff. The law was applied in two phases. The first phase addressed large cities and counties. The second phase, often referred to as ”Phase II,” requires medium and small cities and counties, fast growing cities and those located near sensitive waters to take steps to reduce stormwater. In Washington state, Phase II laws took effect in 2005 but the first permit was not issued until 2007. The initial Phase II Permit was issued in 2007 and reissued in 2012.

These laws require cities to do five things:

  1. Conduct outreach and education about polluted stormwater runoff.
  2. Provide opportunities for residents to participate and be involved in conversations and activities related to reducing polluted stormwater runoff.
  3. Detect illicit discharges (e.g. straight piping or dumping).
  4. Control construction site runoff.
  5. Operations and Maintenance of post-construction Stormwater Facilities.

Streams and creeks feed into rivers, lakes and the ocean. We all drink water, so we are all affected when our water is polluted. When water treatment costs rise, the price of drinking water goes up.

If you like to fish, swim, or boat, you may have heard or been affected by advisories warning you not to swim, fish, or boat in a certain area because of unhealthy water or too much algae. Shellfish like clams and oysters cannot be harvested from polluted waters, so anyone that enjoys these foods or makes a living from the shellfish industry is affected.

Money made from tourism and water recreation can also be impacted, as are businesses and homes flooded by stormwater runoff. When we pollute our water, everyone is affected!

As water from rain and melting snow runs across these hard surfaces and over lawns and gardens they pick up pollutants such as sediments, pet waste, oil, grease, pesticides, and fertilizers. Stormwater carries these contaminants to our streams, rivers, lakes, wetlands, and our aquifers.

More stormwater runs off each year from new impervious surfaces, increasing the demand on the City’s stormwater infrastructure. Since individual contributions to stormwater are small, it is hard for people to believe that we really impact the quality and quantity of stormwater entering our water systems.

The cumulative and long-term effects have a substantial impact to the health of our waterways.

If you own a car, maintain it so it does not leak oil or other fluids. Be sure to wash it on the grass or at a car wash so the dirt and soap do not flow down the driveway and into the nearest storm drain. Better yet, wash your car at a commercial car wash, where the wash water is recycled and eventually flows to a waste water treatment plant.

If you own a yard, do not over fertilize your grass. Never apply fertilizers or pesticides before a heavy rain. If fertilizer falls onto driveways or sidewalks, sweep it up instead of hosing it away. Mulch leaves and grass clippings and place leaves in the yard at the curb, not in the street. Doing this keeps leaves out of the gutter, where they can wash into the nearest storm drain. Turn your gutter downspouts away from hard surfaces, seed bare spots in your yard to avoid erosion and consider building a rain garden in low-lying areas of your lawn.

If you have a septic system, maintain it properly by having it pumped every three to five years. If it is an older system, be sure it can still handle the volume placed on it today. Never put chemicals down septic systems, they can harm the system and seep into the groundwater.

Pet owners should pick up after their pets and dispose of pet waste in the garbage.

Keep lawn and household chemicals tightly sealed and in a place where rain cannot reach them. Dispose of old or unwanted chemicals at household hazardous waste collections sites or events.

Never put anything in a storm drain.

Don’t litter.

Participate in the next stream or beach cleanup in your area. Storm drain marking events – where the destination of storm water is clearly marked on the drain – are a fun way to let your neighbors know the storm drain is only for rain.

Attend public hearings or meetings on the topic so you can express your concerns. Report stormwater violations to the City ((425) 295-0500) when you spot them. Keep learning about polluted stormwater runoff and tell a friend!

Fortunately, something can be done to keep stormwater flooding and pollution problems from becoming worse.

We can:

  1. Manage stormwater to control flooding and erosion;
  2. Plan and construct stormwater systems so contaminants are removed before they pollute our surface waters or our groundwater resources, acquire and protect natural waterways where they still exist or can be rehabilitated;
  3. Look for opportunities to build "soft" structures such as ponds, swales or wetlands to work with existing or "hard" structures, such as pipes and concrete channels;
  4. Enhance and enforce existing ordinances to make sure property owners consider the effects of stormwater before, during and after development of their land;
  5. Educate ourselves about how our actions affect the quality of our water, and about what we can do to improve water quality; and
  6. Plan carefully to create solutions before problems become too great.

The National Pollutant Discharge Elimination System (NPDES) is a federal permit that regulates stormwater and wastewater discharges to waters of the State. While it is a federal permit, the regulatory authority has been granted to the Washington State Department of Ecology.


The most recent NPDES Phase II Municipal Stormwater Permit for Western Washington was issued by the Department of Ecology on September 1,2012. The updated 2013-2018 permit became effective on August 1, 2013. The permit requires that all affected municipalities create and implement a Stormwater Management Program (SWMPR) which addresses five required program elements:

  1. Public Education and Outreach
  2. Public Involvement and Participation
  3. Illicit Discharge Detection and Elimination
  4. Construction Site Run-Off
  5. Operations and Maintenance of Post Construction Stormwater Facilities.

While the Permit went into effect on August 1, 2013, the permit itself phases program implementation requirements out over the next four years. The Permit also required communities to adopt low impact development code-related requirements with the intent to make LID the preferred and commonly-used approach to site development. The intent of these revisions was to address LID as both a stormwater and land use management strategy for controlling stormwater runoff from new and redevelopment.


We are taking a detailed look at specific areas in the City to determine the best way to handle stormwater from existing and future development. Watershed plans will enable us to make better choices about how to plan, maintain, and construct our drainage systems so they can better meet the community’s many needs.


We are improving the way we maintain ponds, swales, catch basins, drywells, ditches and culverts. We are mapping the location of each stormwater facility, monitoring their condition and tracking the time it takes to maintain them. This will help us determine which ones are working well, which ones aren’t and which ones we need to replace immediately to save money.

When you have a stormwater concern in your neighborhood, call the stormwater utility to find out what can be done. We use your calls to help us determine which facilities need to be replaced or repaired, call (425) 295-0500 or email Stormwater Management Team.

To report a spill call the Spill Hotline or report a spill:

Week days: 8:30am to 5:00pm - call (425)295-0500
Evenings and Weekends: call (425) 295-0700

We are informing the public about drainage systems, how they function and how to take care of them. This will help reduce threats to water quality and prevent flooding problems.

Acknowledging growing concerns with stormwater in our daily lives, we have completed the Stormwater Management Program (SWMPR) document and the current Western WA Phase II Permit Annual Report. Both documents will be updated annually to address additional phased permit requirements as they come into effect.

Please submit your comments to Stormwater Management Team or address written comments to: City of Sammamish Public Works, Senior Stormwater Program Manager, 801 228th Ave SE, Sammamish WA 98075.

Our overall goal for the program is not only to meet the requirements of the municipal stormwater permit administered by the Department of Ecology, but also to ensure that our program addresses your concerns.

Sammamish Public Works staff have been working with other jurisdictions around the Puget Sound through several regional forums in a collaborative effort to share resources, tools, and methodologies to meet Ecology’s SWMPR requirements.

While the SWMPR will be updated and expanded every year, this document will primarily include descriptions of our existing programs and our plan to update these programs to meet the requirements of the Permit.

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