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What is one of the biggest sources of Puget Sound pollution?

The rain.

Rain that runs off roads, roofs, yards, construction sites and bare soil. It picks up the pollution of our daily lives from cars, lawn chemicals, septic tanks and animals. Without trees and moss and ferns to slow the flow, streams are flooded with fast moving water. If the water can’t soak into soils, groundwater and summer stream water supplies suffer.

As part of our ongoing commitment to protect public health and improve environmental conditions in our streams, rivers, lakes and Puget Sound, King County has developed a stormwater management program to meet requirements of the Washington State Department of Ecology (Ecology) National Pollutant Discharge Elimination System (NPDES) Phase I Municipal stormwater permit.

We review and update the program every year, and the public may review and comment on how we manage and deal with polluted runoff.

  1. What is stormwater runoff?
  2. Where does stormwater runoff in King County go?
  3. Is stormwater a threat to the environment?
  4. Is stormwater runoff treated for pollution?
  5. What is an NPDES Municipal Stormwater Permit?
  6. Why did the Washington State Department of Ecology issue King County a NPDES Municipal Stormwater Permit?
  7. What will the permit do to clean up Puget Sound?
  8. What’s happening with the new permit?
  9. The 2013 permit talks a lot about Low Impact Development (LID). What is LID?
  10. Will LID replace existing stormwater infrastructure?
  11. What is a Total Maximum Daily Load (TMDL)?
  12. Will the permit affect development proposals?
  13. Will the permit prevent flooding?
  14. What other municipalities are regulated under NPDES municipal permits?
  15. What is a SWMP?
  16. Will my Surface Water Management bills change?
  17. What are the repercussions of non-compliance?

  1. What is stormwater runoff?
    In a natural setting, most rainfall and snowmelt seeps into the ground or evaporates back into the air through the plants and trees. However, when vegetation is removed and the ground is cleared, compacted, or covered with a hard/impervious surface, rainfall and snowmelt can’t infiltrate – creating stormwater. This runoff can pick up various pollutants as it flows across hard and impervious surfaces, such as roads, rooftops, parking lots and lawns.  Depending on the type and location of the hard/impervious surface, the pollutants may include pesticides, fertilizers, bacteria and viruses from pet waste, metals and oil from vehicles, trash and other chemicals.
     
  2. Where does stormwater runoff in King County go?
    Stormwater runoff does not go to a treatment plant. No matter what route it takes, stormwater runoff eventually reaches Puget Sound. It flows across and through a system of manmade structures such as sidewalks, driveways, roads, ditches and pipes, before emptying into local streams, rivers, and lakes which ultimately drain to Puget Sound. Even stormwater that soaks into the  ground can quickly emerge in a nearby stream or lake and will eventually drain to the Sound.
     
  3. Is stormwater a threat to the environment?
    Stormwater runoff has been identified as the number one contributor of pollution to Puget Sound. The volume of stormwater runoff increases as land is developed and converted from naturally forested conditions into properties with hard or impervious surfaces. More runoff  means more pollutants making their way into local water bodies on route to Puget Sound. Higher pollutant levels threaten  the health and safety of people, and of the fish and wildlife that live in streams, lakes, and in the Sound. Increased flow rates causes erosion and sedimentation, destroys the habitat functions of local waterways, and disrupts the Puget Sound ecosystem. For more information on the regional effort to restore and protect Puget Sound, visit the Puget Sound Partnership website (external).
     
  4. Is stormwater runoff treated for pollution?
    Unlike wastewater, stormwater runoff is not sent to high-tech treatment plants to remove pollutants before being discharged to Puget Sound. Prior to 1990, stormwater management focused only on conveyance – draining stormwater runoff efficiently to minimize flooding.   Approximately 70 percent of the development within unincorporated King County was completed before 1990 and, therefore, the stormwater runoff from these areas is discharged into local water bodies without treatment.

    As increased development generated more and more stormwater runoff, it became apparent that stormwater management needed to address more than just flooding concerns.  Potentially harmful pollutants carried by stormwater runoff and high flows that damaged wildlife habitat within and along streams were growing problems.  Beginning in 1990, regulations started to require stormwater systems that reduced pollutant loads and minimized/slowed the volume of stormwater runoff flowing off sites during and after development. Typically, this is achieved through implementation of one or more stormwater management features or principles, such as setting aside undeveloped parts of the site, infiltrating stormwater onsite, or connecting the site to a regional stormwater facility that controls both the quantity and quality of stormwater runoff.
     
  5. What is an NPDES Municipal Stormwater Permit?
    Congress established the National Pollutant Discharge Elimination System (NPDES) in 1972 as part of the Clean Water Act. The NPDES Stormwater Program is a national program for addressing stormwater discharges. The municipal NPDES program issues permits to municipalities, including cities, counties, ports and other governmental entities and requires them to undertake efforts to reduce stormwater pollution by implementing steps referred to as best management practices (BMPs), which refer to a wide variety of pollution prevention systems or efforts. These can range from physical structures such as treatment ponds, to non-structural actions such as education programs designed to teach people how to reduce pollution. Please see the U.S. Environmental Protection Agency’s (EPA) NPDES permit program website for more information.
     
  6. Why did the Washington State Department of Ecology issue King County a NPDES Municipal Stormwater Permit?
    The Clean Water Act allows the EPA to delegate NPDES permitting to individual states that meet specified requirements. The State of Washington has met those requirements and the Washington State Department of Ecology is authorized to implement the NPDES permit program in the state.
     
  7. What will the permit do to clean up Puget Sound?
    The municipal stormwater permits are intended to reduce the volume of stormwater-borne pollutants entering natural water bodies, including Puget Sound. If they achieve their goal, the reduction of pollutants flowing into Puget Sound from stormwater should reduce overall pollution in the Sound, particularly for pollutants such as nutrients, metals and bacteria that are commonly associated with stormwater runoff. It is important for all of King County’s citizens to realize the role they play in protecting local water quality.  King County has supported educational efforts like www.pugetsoundstartshere.org to help share this message.
     
  8. What’s happening with the new permit?
    A new permit took effect on Aug. 1, 2013 and it covers the County’s stormwater discharges through July 31, 2018. This permit contains new and expanded requirements which will require the County to create and implement significant new programs/activities as part of its SWMP.  A copy of the 2013 permit can be found on the Dept. of Ecology website (external link).

    The 2013 permit carries forward many requirements of previous municipal stormwater permits and significantly expands the scope of a number of programs including:
    • Mapping
    • New development, redevelopment, and construction
    • Structural stormwater controls
    • Illicit connections and illicit discharges detection and elimination
    • Operations and maintenance
    • Public education and outreach
    • Watershed scale stormwater planning
    • Total maximum daily loads
    • Monitoring
       
  9. The 2013 permit talks a lot about Low Impact Development (LID). What is LID?
    Low Impact Development is an approach to stormwater management that focuses on controlling stormwater at or near its source.  LID minimizes runoff by preserving as much natural area as possible, by partially restoring cleared soils with the addition of soil amendment and replanting un-built areas; and it handles runoff of collected water from developed areas by using dispersion, infiltration, plant uptake, and small-scale storage and release.

    The new permit requires that LID be used wherever feasible for stormwater management during site development and redevelopment. This places more stormwater treatment and flow control from impervious surfaces on decentralized, privately-owned and maintained systems, instead of the current system in which stormwater runoff is often routed to regional stormwater control facilities maintained by local governments.  For more information on LID, please visit EPA's Low Impact Development website (external).
     
  10. Will LID replace existing stormwater infrastructure?
    Traditionally, stormwater runoff has been managed on a regional scale, with treatment and/or flow control facilities serving large areas.  Using LID, treatment and/or flow control facilities are smaller and decentralized to control stormwater runoff at or near its source.  As new development and redevelopment occurs, more and more properties will incorporate LID but that does not necessarily eliminate the need for regional facilities to provide treatment and/or flow control during large rain events.  Additionally, regional stormwater facilities minimize localized flooding.
     
  11. What is a Total Maximum Daily Load (TMDL)?
    Per the Clean Water Act, the Washington State Department of Ecology (Ecology) is required to identify water bodies that are impaired by pollutants and develop programs to return the waters to beneficial uses (fishable, swimmable, etc.). Central to these recovery plans are TMDLs which are an estimation of how much of a pollutant like bacteria or nitrogen that a body of water can receive daily, and still meet its designated uses. Based on these loading estimates, Ecology prepares a written plan with requirements for each pollutant contributor to enact.  The plan is then approved by the EPA. King County is implementing stormwater management actions for four TMDL-listed water bodies: Bear-Evans Creeks, Issaquah Creek, and the Puyallup/White River system (all impaired by fecal coliform bacteria); and, Cottage Lake (impaired by total phosphorus).
     
  12. Will the permit affect development proposals?
    The 2013 permit requirements result in modifications to the stormwater requirements for development and redevelopment projects, and also result in drainage or erosion and sedimentation control inspections for projects that trigger certain thresholds.

    King County is revising its development guidelines for managing stormwater in its Surface Water Design Manual, which will be revised to achieve equivalency with Ecology’s own manual, which itself has been revised to incorporate new LID standards and other revisions.  More information will be available at the Surface Water Design Manual website as the manual is updated.
     
  13. Will the permit prevent flooding?
    The NPDES Phase I Municipal Stormwater Permit is focused on improving stormwater quality and quantity, largely through management of King County’s stormwater conveyance system. By controlling flows, King County’s stormwater conveyance system helps to minimize localized flooding as well as discharges to major rivers that experience large-scale flooding. King County also provides extensive flood management services. For more information on this work, visit King County’s flooding services website.
     
  14. What other municipalities are regulated under NPDES municipal permits?
    The NPDES permits were issued in two phases. Under Phase I, only municipalities with populations of 100,000 or larger based on the 1990 census were covered under the municipal stormwater permit. In Washington, this included Clark, King, Pierce, and Snohomish counties, the cities of Seattle and Tacoma, and the Washington State Department of Transportation. In 2007, new Phase II permits extended municipal stormwater permit coverage to include most municipalities in the Puget Sound Basin. Additional municipalities continue to be covered under the Phase II permits as their populations increase.  To see the extent of Phase II coverage in King County, please refer to the following on the Dept. of Ecology website: For a list of permittees, see who's covered under the Municipal Stormwater Permits on the Dept. of Ecology website.
     
  15. What is a SWMP?
    King County’s NPDES Phase I Municipal Stormwater Permit requires the County to develop a series of programs and projects designed to manage stormwater. These actions and activities comprise the County’s Stormwater Management Program (SWMP). Every year, King County documents its SWMP in a plan to inform the Washington State Department of Ecology, elected officials, and members of the general public what actions and activities are planned for the coming year.  Annual updates to the SWMP are posted on King County’s Stormwater Management Program website no later than March 31st of each year.
     
  16. Will my Surface Water Management bills change?
    Recently, the Metropolitan King County Council approved a Surface Water Management (SWM) fee increase. Please visit the SWM fee website for more information.
     
  17. What are the repercussions of non-compliance?
    Ecology and third parties, including citizens and environmental groups, can sue municipalities for not complying with permits. Penalties for non-compliance include fines of up to $32,500 per violation, per day.

For information about stormwater in King County, please contact us at Stormwater@kingcounty.gov.