North Thornton Natural Drainage Systems
Example of a natural drainage system a few years after installation
አማርኛ | اللغة العربية | 繁體中文 | 한국어 | русский язык | Soomaali | Español | ትግርኛ | Tiếng Việt
Project description
Improving creek water quality, reducing drainage issues, and providing other community benefits.
More than 12 million pounds of pollution are carried into our water systems by stormwater runoff every year. Stormwater that falls on hard surfaces in your neighborhood - like roofs, streets, and parking lots - can pick up harmful pollutants before it runs into Thornton Creek, which flows into Lake Washington and eventually into Puget Sound. The pollutants can harm fish, wildlife, and our ecosystems.
SPU is working to minimize pollution at its source. Natural drainage systems (NDS) are shallow depressions built in the roadway shoulder (the public space between the street edge and property line). They are filled with special soil and deep-rooted plants to temporarily hold and filter stormwater, reducing pollution in Lake Washington and Puget Sound.
The North Thornton Natural Drainage Systems Project aims to:
- Build natural drainage systems to reduce the amount of pollution in Thornton Creek and Lake Washington and improve stormwater drainage in your neighborhood.
- Provide other community benefits, which include reduction of drainage issues, traffic calming, more street trees, and added landscaping.
Location
The North Thornton Natural Drainage System project is focused on reducing pollution in the north branch of Thornton Creek. (Map of Thornton Creek Watershed)
As part of this project, SPU will build natural drainage systems at two sites in Lake City neighborhoods. Check out the links below for the proposed designs at each project location.
- Little Brook
- 32nd Ave NE between NE 135th St and NE 137th St
- Olympic Hills
- 25th Ave NE between NE 127th St and NE 130th St
- NE 127th St between 25th Ave NE and 27th Ave NE
- 27th Ave NE between NE 125th St and NE 127th St
This map shows the locations selected for natural drainage systems.
What's happening now?
Project Update
SPU has completed our technical feasibility studies in the North Thorton Creek basin and has selected two project sites to move forward into the project’s design phase:
- Little Brook
- 32nd Ave NE between NE 135th St and NE 137th St
- Olympic Hills
- 25th Ave NE between NE 127th St and NE 130th St
- NE 127th St between 25th Ave NE and 27th Ave NE
- 27th Ave NE between NE 125th St and NE 127th St
Originally, we planned to include more blocks in this project. However, through our technical analysis we discovered that installing natural drainage systems in the North Thornton Creek basin is challenging because of high groundwater elevation and underground utilities. Additionally, some of the blocks we studied would not be able to treat enough stormwater to be cost-effective. Due to these factors, we eliminated many blocks and ultimately chose two sites to move forward into design.
The project is in the mid-design phase, with construction tentatively expected to begin in 2026. Over the next several months, the project team will be working on:
- Community and Business Engagement: Continue coordinating with local businesses and homeowners to gather design feedback and address easement needs
- Design Advancement: Progress the design, incorporating feedback from the community, Seattle Public Utilities (SPU) stakeholders, and permitting agencies
- Community Outreach Planning: Prepare for the next round of community outreach, tentatively scheduled for spring 2025
Community benefits
Natural drainage systems will reduce pollution in Thornton Creek and Lake Washington and help manage stormwater. This project will provide additional benefits to local neighborhoods and ecosystems, including:
- More plants and plant diversity
- Reduced drainage issues
- Healthier creek ecosystems
- Improved pedestrian safety and mobility
- More street trees
Community engagement
Thank you to everyone who shared their valuable feedback during the project’s planning and early design phases. During these project phases, we administered online and mailed surveys and learned about specific concerns and interests from neighbors around the project area. Here are some common themes we heard from community members:
- Parking: There is concern about the loss of parking adjacent to businesses and residences
- Business access: There is concern about construction and long-term impacts on business access, especially related to deliveries
- Sidewalks: There is support and excitement for new sidewalks in the project area. Neighbors would like partial-block sidewalks extended to the full block and further, if possible.
- Trees and plants: Neighbors requested that the project minimizes impacts to trees to the extent feasible
- Traffic circles: Neighbors would prefer that the plantings remain in the traffic circle at the intersection of NE 127th St and 25th Ave NE
- Drainage concerns: Neighbors shared observations of drainage concerns on streets, specifically on the east side of 25th Ave NE between NE 127th St and NE 130th St
Community engagement will continue to be important during the project’s design and construction phases. In 2024 and 2025, we will reach out to community members in the project area to ask for feedback on our proposed design. Please sign up for the project email list to receive updates about opportunities to share your feedback.
If you would like translated information about the North Thornton Natural Drainage Systems project, please call Wan-Yee Kuo, the project manager, at (206) 684-3957 or view the translated resources below.
አማርኛ (Amharic)
በሌክ ሲቲ ሰፈር ውስጥ በሁለት ቦታዎች ላይ የተፈጥሮ የፍሳሽ ማስወገጃ ዘዴዎችን እየገነባን ነው። ስለዚህ ፕሮጀክት የበለጠ መረጃ ከፈለጉ እባክዎን የፕሮጀክት ስራ አስኪያጅ ለሆነው Wan-Yee Kuoን በ (206) 684-3957 ይደውሉ።
اللغة العربية (Arabic)
نقوم ببناء أنظمة الصرف الطبيعي في منطقتين ضمن حي ليك سيتي. يرجى التواصل مع السيدة وان-يي كو، مديرة المشروع، على الرقم 2066843957 للحصول على المزيد من المعلومات حول هذا المشروع.
繁體中文 (Chinese - Traditional)
我們正在湖城市 (Lake City) 附近的兩個地點建造自然排水系統。如果您想了解更多有關本工程的資訊,請撥打 (206) 684-3957 與工程經理 Wan-Yee Kuo 聯絡。
한국어 (Korean)
Lake City 지역의 두 곳에 자연 배수 시스템을 구축할 것입니다. 이 프로젝트에 대한 자세한 정보를 원하시는 경우, 프로젝트 매니저인 Wan-Yee Kuo에게 (206) 684-3957로 전화해 주십시오.
русский язык (Russian)
Мы сооружаем системы естественного дренажного отвода природной воды на двух участках территории района Lake City. Если вы хотите получить дополнительную информацию о данном проекте, пожалуйста, позвоните руководителю данного проекта, Wan-Yee Kuo, по телефону (206) 684-3957.
Soomaali (Somali)
Waxaan ka dhisaynaa nidaamyada biyo-mareenada dabiiciga ah laba goobood oo ku yaal xaafadda Lake City. Fadlan wac Wan-Yee Kuo, maareeyaha mashruuca, lambarka (206) 684-3957 haddii aad rabto macluumaad dheeraad ah oo ku saabsan mashruucan.
Español (Spanish)
Estamos construyendo sistemas de drenaje natural en dos ubicaciones en el vecindario de Lake City. Por favor llame a Wan-Yee Kuo, gerente del proyecto, al (206) 684-3957 si desea obtener más información sobre este proyecto.
ትግርኛ (Tigrinya)
ኣብ ከባቢ ሌክ ሲቲ ኣብ ዚርከቡ ክልተ ቦታታት ተፈጥሮኣዊ ስርዓታት መወገዲ ፈሳሲ ንሃንጽ ኣሎና። ብዛዕባ እዚ ፕሮጀክት እዚ ዝያዳ ሓበሬታ ክትረክብ እንተ ደሊኻ ብኽብረትካ ነቲ ኣካያዲ ስራሕ ፕሮጀክት ዝዀነ Wan-Yee Kuo ኣብ (206) 684-3957 ደውለሉ።
Tiếng Việt (Vietnamese)
Chúng tôi đang xây dựng hệ thống thoát nước tự nhiên tại hai địa điểm trong khu phố Lake City. Vui lòng gọi cho Wan-Yee Kuo, người quản lý dự án, theo số (206) 684-3957 nếu quý vị muốn biết thêm thông tin về dự án này.
2020
- Early project planning and community engagement
2021
- Technical analysis of the project area to identify potential locations for natural drainage systems
2022
- Community survey and updates
- Coordination with other City departments
- Early project design
2023
- Final selection of locations for natural drainage systems
- Project design
2024-2025
- Complete project design
- Ongoing updates to community and opportunities for community engagement
- Hire contractor and prepare for construction
2026
- Construction begins
* Tentative schedule as of May 2024. This schedule is subject to change.
Natural drainage systems are living systems, and their appearance will change over time. The grasses, shrubs, and trees in the natural drainage system will grow and change as the garden matures. It may take up to three years for plants and shrubs in the natural drainage system to reach full maturity, and possibly longer for trees. The examples below show what a natural drainage system may look like over time.
Maintenance and Care
SPU is responsible for all maintenance needs of the natural drainage systems, including watering, weeding, and general upkeep. SPU will also prune trees and shrubs within the natural drainage system as needed. You will not be asked to perform any maintenance of the natural drainage systems. It is important for residents to stay out of the natural drainage system to maintain the function of the systems. Plants will mature over time and the mix of plants will likely change, but this won’t affect the system’s function.
As is typical for Seattle, property owners are responsible for maintaining portions of the planting strip, roadway shoulder, and grass-lined drainage ditches that are not part of the natural drainage system.
Natural drainage systems slow stormwater and filter out pollutants before they can harm our creeks and other waterways. Keeping pollutants out of our water is important for fish, aquatic life, and people.
Building a natural drainage system in the Thornton Creek basin is part of the Plan to Protect Seattle's Waterways. SPU used to call these "roadside rain gardens" but now calls them "natural drainage systems."
Why Thornton Creek? Thornton Creek is a salmon-bearing urban creek with degraded water quality. Stormwater picks up pollutants from streets—including oil, heavy metals, and fertilizers—and flows into the creek through ditches or pipes. This project will remove pollutants from stormwater before it reaches Thornton Creek.
Fact sheets
Frequently asked questions
- Frequently Asked Questions
- Frequently Asked Questions Español
- Frequently Asked Questions 繁體中文
- Frequently Asked Questions Tiếng Việt
- Frequently Asked Questions አማርኛ
- Frequently Asked Questions ትግርኛ
- Frequently Asked Questions Soomaali
- Frequently Asked Questions русский язык
- Frequently Asked Questions 한국어
- Frequently Asked Questions اللغة العربية