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Sammamish Town Center (not licensed)

Stormwater Frequently Asked Questions

Sr. Stormwater Program Manager

Stephanie Sullivan
(425) 295 0560

Frequently Asked Questions

How to report a spill

To report a spill call the Spill Hotline or use My Sammamish:

Weekdays 8:30am to 5:00pm: call (425) 295-0500
Evenings and weekends: call (425) 295-0700

What is stormwater?

Stormwater is rainwater or snowmelt. When stormwater flows on the ground, it’s called surface water or stormwater runoff. It can soak into the ground and become groundwater. Some stormwater is dissipated back into the air through evapotranspiration.

What is runoff?

Stormwater runoff can pick up substances that pollute water. When it carries them to streams, lakes, and other water bodies, it’s called “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.

Not only rain and snowmelt can become stormwater runoff. Additionally, human activities like pressure washing, car washing, and malfunctioning septic tanks can release water on 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, water that falls on hard surfaces like roofs, driveways, parking lots or roads cannot seep into the ground. These impervious surfaces create large amounts of runoff that pick up pollutants. The runoff flows from gutters and storm drains to streams. Runoff not only pollutes but erodes stream banks. The mix of pollution and eroded dirt muddies the water and causes problems downstream.

What causes polluted stormwater runoff?

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. Common examples include:

  • fertilizing lawns too much,
  • using too much pesticide,
  • leaving pet waste on the ground,
  • driving cars on roads,
  • letting oil drip from vehicles, and
  • littering.

Developed areas are a major contributor to non-point source pollution. Agricultural activities are too. This is due to their increased runoff, concentrated numbers of people and animals, construction and other activities. Other contributors include forest harvesting activities, roadways, and malfunctioning septic systems.

Why do we need to manage stormwater and polluted runoff?

Stormwater runoff is not treated

Polluted stormwater runoff is the number one cause of water pollution in Washington. In most cases, stormwater is not treated or inadequately treated before entering our waterways.

Polluted water impacts everyone

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 clean up polluted water more than clean water before drinking.

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. This 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.

There is too much stormwater

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. This creates more volumes of surface runoff.

Every year, new impervious surfaces are built. That means more stormwater runs off. This increases demand on the City’s stormwater infrastructure.

As Sammamish builds more roofs, driveways, and hard surfaces, the land’s capacity to soak up and carry away excess water decreases. Conditions that could have caused a flood every 100 years in an undeveloped area can cause flooding every 4-5 years in developed areas covered with impervious surfaces. The high volume of water also causes stream banks to erode. Rushing water washes the wildlife that live there downstream.

How are stormwater and runoff "managed"?

“Best management practices” describe ways to keep pollutants out of runoff and slow down high volumes.

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.

The city also uses codes to prevent stormwater pollution. City codes require people and businesses in earth-disturbing activities (like construction) to take steps to prevent erosion. 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. Solids like sediment and litter settle at the pond's bottom. Then, the water slowly drains. These facilities are one constructed BMP example. There are also acceptable and allowable discharges to the MS4.

What is a Best Management Practice (BMP)?

A best management practice (BMP) is an activity that prevents pollution from impacting surface water, stormwater, and groundwater. BMPs may be actions used alone or in combination, or could include a schedule of activities. They may be maintenance procedures, prohibition of practices, or structure and/or managerial practices.

What is nonpoint source pollution?

Nonpoint source pollution is another term for polluted runoff. It can also refer to other sources of water pollution that don’t 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.

Why all the recent fuss about stormwater?

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, “Phase II,” requires medium and small cities and counties, fast-growing cities and those 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.
If it only affects streams and creeks, why should I care?

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.

Unhealthy water or too much algae can trigger advisory warnings to not swim, fish, or boat in certain areas. If you enjoy any of these activities, this can affect you.

Shellfish like clams and oysters cannot be harvested from polluted waters. 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. So are businesses and homes flooded by stormwater runoff. When we pollute our water, everyone is affected!

What causes pollution problems?

Water from rain and melting snow picks up pollution when it runs across hard surfaces, lawns and gardens. The water collects pollutants like sediments, pet waste, oil, grease, pesticides and fertilizers. Stormwater then carries these contaminants to our streams, rivers, lakes, wetlands, and aquifers.

Individual contributions to stormwater might be small, but pollution adds up from the whole community. We each 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.

What can I do to reduce the amount of stormwater pollution I contribute?

If you own a car:

  • Maintain it so it does not leak oil or other fluids.
  • Wash it on the grass 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. There, the wash water is recycled then flows to a wastewater 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. Place leaves from 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.
  • Consider building a rain garden in low-lying areas of your lawn.

If you own a private road or driveway:

  • Salting roads is not addressed in the NPDES Permit or city code, so the activity is not regulated. Although this activity is not regulated, the city encourages residents to consider other methods of snow removal
  • In winter months and icy conditions consider shoveling. Salting is nowhere near as effective as a shovel. • Do nothing - most modern cars can navigate a few inches of snow without difficulty. 
  • Stay home! This is safest for everyone, including the environment! 
  • If you must use salt, please only use it as a last resort and apply the minimum amount necessary.

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 collection sites or events.

Never put anything in a storm drain.

Don’t litter.

Learn more about ways you can help protect our waterways from pollution.

How else can I help reduce stormwater pollution in my area?

Participate in the next stream or beach cleanup in your area.

Storm drain marking events are a fun way to let your neighbors know the storm drain is only for rain. At these events, volunteers mark storm drains with the destination of storm water.

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!

What can be done about the problems?

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.
What is NPDES?

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.

NPDES Phase II Municipal Stormwater Permit Program 

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. The intent is to make LID the preferred and commonly-used approach to site development. These revisions addressed LID as both a stormwater and land use management strategy for controlling stormwater runoff from new and redevelopment.

Learn more about how the City complies with stormwater policies.

What else is the city doing now to address a stormwater runoff?

Basin Planning

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 help us make better choices on planning, maintaining, and constructing our drainage systems. This will enable us to better meet the community’s 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.

Public involvement and awareness

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.

In acknowledgment of growing concerns over stormwater impact, we’ve 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: the City of Sammamish Public Works, Senior Stormwater Program Manager, 801 228th Ave SE, Sammamish WA 98075.

Our overall goal is to both meet the requirements of the municipal stormwater permit and ensure that our program addresses your concerns.

Sammamish Public Works staff have been participating in regional forums with other jurisdictions around Puget Sound. These represent 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.


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