The City of Kent is required to implement a Stormwater Planning Program to inform and assist in the development of policies and strategies as water quality management tools to protect receiving waters. The Stormwater Planning Program is a watershed-scale approach to stormwater management that aims to protect designated uses and improve water quality under both current and future developed conditions. Stormwater Planning requirements include convening an inter-disciplinary team, coordination with long range plan updates, low impact code-related requirements, and Stormwater Management Action Planning. 

Through the Stormwater Management Action Planning process, the city assessed water quality at the watershed level and identified Mill Creek as a high priority receiving water that would receive the most benefit from intervention. With guidance from the City’s inter-disciplinary team of technical experts and feedback from residents and stakeholders, the city developed a Stormwater Management Action Plan, (SMAP) for the Lower Mill Creek basin. 

The SMAP outlines actions that can be implemented to protect or improve water quality, including stormwater management actions, land management strategies, and best management practices (BMPs) that are tailored to the Lower Mill Creek basin. To learn more about the current and potential actions identified to improve water quality in the Lower Mill Creek Basin, the Mill Creek SMAP is available for review here: Mill Creek Stormwater Management Action Plan.

The City strives to connect with citizens on stormwater issues and instill an appreciation for our vital water resources to reduce pollution in our local waterways. We work with Kent schools, neighborhood groups, businesses, and the public to provide education opportunities that build general awareness about the impacts of stormwater on surface water and methods to reduce negative impacts on local waterways. If you are interested in having someone meet with you or your group, please contact us. 

What you can do today!

• Get more information - you're already here so you're off to a great start! Learn about stormwater and ways to prevent pollution:
  • Watch King County's 5-minute video What is stormwater and why is it important? 
  • Kid Friendly Links:
    • Freddy the Fish Teaches about Stormwater
    • A Ground Water Education
  • Check out our Only Rain Down the Drain Brochure.
• Spread the word - Talk to your family, friends, neighbors, and coworkers about stormwater issues and ways to prevent pollution in stormwater, such as picking up after pets or proper use, storage, and disposal of common household products that contain chemicals and hazardous materials.
• Be a drain ranger - watch for spills or stormwater pollution and report it!
  • For emergencies, call 911
  • For urgent spills, call the Spill Hotline at 253-856-5600 or submit online report
• Meet our team - come visit the Environmental Engineering booth at one of Kent's many community events and let us know if there is an event you would like us to join:
  • Kent Cornucopia Days
  • Kent Farmers Market
  • Paw Fest
  • Cruisin' Kent Car Show
  • Street of Treats
  • Winterfest
• Get involved - make a direct impact on the environment and water quality in Kent by participating in any of our stewardship events:
  • Kent Adopt a Street Program
  • Team Up to Clean Up
  • King County Wastemobile
  • Recycling and hazardous waste collection events
  • Earth Day
  • Conservation Day
  • Orca Recovery Day
  • ReLeaf
  • Arbor Day
  • Storm Drain Markers

The City welcomes and values citizen engagement in stormwater management and the City's Stormwater Management Program (SWMP) Plan. We need public participation to be successful in protecting and improving the quality of our precious water resources.

Ways that you can get involved and participate: 

• Review  Kent's Stormwater Management Program (SWMP) Plan
• Review the 2023 Kent Annual NPDES Report and supporting attachments:
  • City of Kent 2023 Annual Report Question 21
  • City of Kent 2023 Annual Report Question 25
  • City of Kent 2023 Annual Report Question 26a
  • City of Kent 2023 Annual Report Question 30a
  • City of Kent 2023 Annual Report Question 42
  • City of Kent 2023 Annual Report Question 77
  • City of Kent 2023 Annual Report Question 78 
• Attend, or watch online, the City Council and Public Works Committee Meetings 
• Contact us with questions, concerns, and comments at NPDES@KentWA.gov

Maps of the public stormwater drainage system can help:

• Trace illicit discharges and spills containing pollutants upstream.
• Find the source of the pollutants.
• Identify where pollutants will travel downstream of discharge.
• City staff uses this information to isolate, divert, and remediate non-stormwater discharges.
• Protect waters of the state such as rivers, lakes and streams from being contaminated by pollution.

The city’s Geographic Information System (GIS) Division maintains an electronic stormwater drainage system database as a visible map layer that depicts all city-owned stormwater drainage system conveyance, stormwater facilities, outfalls, treatment and flow control best management practices (BMPs), and non-groundwater receiving waters. This database is updated regularly to reflect new and altered stormwater infrastructure based upon submittals of map update requests by field staff and as-built plans received from completed construction projects.

Associated drainage basin layers and land use information layers have been developed and can be viewed in conjunction with the other stormwater system elements. In addition, the city’s GIS department is in the process of mapping all low impact development (LID) facilities and privately owned stormwater systems in the city.

Everyone can identify and prevent pollution!

Through Illicit Discharge Detection and Elimination (IDDE) we all work together to protect water quality and preserve our natural resources.

An illicit discharge is any release of a non-stormwater substance into the stormwater drainage system and/or waterways; this can include common household cleaners, car fluids and wash water, paint, garbage, dirt, yard and pet waste. 

Through our 24-hour spill hotline 253-856-5600 and online reporting form we receive reports about spills and illicit discharges and/or connections. City staff respond promptly to spill reports in order to prevent pollution from entering stormwater drainage systems and waterways.    

Illicit Discharges Code

Kent City Code (KCC) Chapter 7.14 – Illicit Discharges, provides very specific information on what can and cannot be discharged into the city's stormwater system.

The code also supports actions for compliance through inspections, monitoring, and required use of stormwater best management practices to prevent pollutants from entering the public stormwater drainage system and waters of the state, such as rivers, lakes, and streams.

Visit our Stormwater Best Management Practices page for information on how to prevent spills and illicit discharges.  

Stormwater Pollution Prevention Plan (SWPPP)

Any development or construction site that disturbs one acre or more of soil must develop a Stormwater Pollution Prevention Plan (SWPPP) as part of their compliance requirements. The SWPPP includes specific BMPs for reducing or eliminating pollution originating from a construction site, most often in the form of dirty stormwater.  The BMPs outlined in the SWPPP must be continuously inspected during construction to ensure proper function and protect water quality. These inspections must be performed by a State approved Certified Erosion and Sediment Control Lead (CESCL). The Washington State Department of Ecology approves these certification courses and keeps an updated list of CESCL certified individuals here. The SWPPP must be regularly updated and kept available upon request at all times during the construction project.

A complete SWPPP will focus on 13 main elements that have the potential to affect stormwater and water quality.  The Department of Ecology SWPPP template can be found here.  The 13 elements include:

1. Preserve Vegetation & Mark Clearing Limits
2. Establish a Construction Access
3. Control Flow Rates
4. Install Sediment Controls
5. Stabilize Soils
6. Protect Slopes
7. Protect Drain Inlets
8. Stabilize Channels and Outlets
9. Control Pollutants
10. Control De-Watering
11. Maintain BMPs
12. Manage the Project
13.  Protect LID BMPs 

Ensuring Compliance

The State requires the City of Kent to inspect and pursue compliance for construction related stormwater violations as part of the NPDES Phase II Municipal Stormwater Permit.  The City of Kent employs highly trained staff to inspect construction sites to ensure all efforts are being made to protect water quality.

The City works diligently to implement maintenance standards for the city’s stormwater drainage system as well as stormwater facilities regulated by the city. These maintenance standards are developed for efficient conveyance, storage, and treatment of stormwater before it is discharged to surface or ground waters. This helps to reduce localized flooding, decrease instances of erosion, and allow treatment processes to function properly. As a result, the city continues to ensure that these facilities are full-functioning and properly maintained and will prevent and/or reduce stormwater pollution.

Maintenance Standards For all stormwater treatment and flow control facilities, catch basins, and inlets, the city adheres to maintenance standards specified in the City of Kent Design and Construction Standards and City of Kent Surface Water Design Manual. These standards establish criteria for identifying maintenance deficiencies and needs.

Maintenance of Stormwater Facilities Owned or Operated by the City

The city implements an Operations and Maintenance Program including inspection and maintenance of stormwater conveyance, treatment and flow control facilities.

The city addresses the maintenance deficiencies discovered during the inspection process. The most common and routine maintenance, such as system cleaning, vegetative maintenance and inlet and outlet structure maintenance, is completed by public works operations staff. However, for facilities that require excessive maintenance, the city may hire contractors to complete the work.

For more information visit the Storm Drainage and Flooding page.

The City of Kent Public Works Engineering Department conducts inspections of private stormwater systems to ensure stormwater facilities are being maintained and functioning properly. Private stormwater systems can include conveyance, treatment and flow control facilities, which reduce peak stormwater flows and capture pollutants carried by stormwater. Proper maintenance of these facilities is necessary to protect our downstream waterways from flooding and water quality impacts, as well as to comply with federal and state regulations. 

For more information visit the Private Drainage page.

Common Facilities (Catch Basins, Ponds, Bioswales, and Vaults)

Less Common Facilities (refer to Appendix A of the King County Surface Water Design Manual)

City of Kent Surface Water Design Manual

Kent Design and Construction Standards Manual

As of January 2023, the city has been implementing a Source Control Inspection Program to prevent and reduce pollutants in runoff from areas that discharge to the public stormwater drainage system. This is a new program that includes the inspection of publicly and privately owned institutional, commercial, multi-family, and industrial sites which have the potential to release pollutants to the public drainage system.

The Source Control Program includes the following four elements:

• The use of operational, structural and treatment source control Best Management Practices (BMPs).

• Inspections of pollutant generating sources at publicly and privately owned institutional, commercial and industrial sites to enforce implementation of required BMPs to control pollution discharging into the public stormwater drainage system.

• Application and enforcement of local ordinances at sites, identified as having the potential to release pollutants into the public stormwater drainage system, including sites with discharges authorized by a separate NPDES permit.

• Practices to reduce polluted runoff from application of pesticides, herbicides, and fertilizers from the sites identified in the inventory.

Per Kent City Code 7.05, all business owners are required to construct, implement, and maintain source control BMPs to prevent pollutants from reaching the MS4. Rain falling on your business property can collect a number of different contaminants, including dirt, oil, fertilizers, pesticides, litter and assorted chemicals and metals. This polluted storm runoff flows into storm drains and ditches that lead to streams, lakes, and wetlands.

The Source Control Program includes education and technical assistance to assist business owners/managers and staff with implementing the proper BMPs.

Best Management Practices … What are They?

Best Management Practices (BMPs) are a set of activities designed to reduce stormwater pollution. BMPs are separated into two broad categories: source control and treatment.

Source Control BMPs

Source control BMPs prevent contaminants from entering stormwater runoff by controlling them at the source. Some source control BMPs are operational, such as checking regularly for leaks and drips from equipment and vehicles, covering materials that have potential to add pollutants to surface water if rainwater comes in contact with the materials, cleaning up pet waste, and minimizing use of pesticides, fertilizers, and insecticides. Other source control BMPs require use of a structure to prevent rainwater from contacting materials that will contaminate stormwater runoff such as provide a covered area or berm to prevent clean stormwater from entering work or storage areas.

Treatment BMPs

In contrast, treatment BMPs are structures that treat stormwater to remove contaminants. Treatment BMPs typically require elaborate planning, engineering design, and construction. A stormwater pond for your subdivision is an example of a treatment BMP. No treatment BMP is capable of removing 100 percent of the contaminants in stormwater; the less contaminant in stormwater prior to the treatment BMP, the more effective the BMP is.

For more information visit the Stormwater Best Management page.