1. Which surface water design manuals are used by the City of Kirkland?
2. Where are the stormwater standard details?
3. What are the classifications of drainage reviews and what are the requirements?
4. How do I find out if there are existing drainage problems downstream from a potential project?
5. When is a construction stormwater general permit required?
6. When is a stormwater pollution prevention and spill (SWPPS) plan required?
7. What temporary erosion control is required during construction in Kirkland?
8. When is a stormwater detention facility required?
9. What level of flow control is required in Kirkland?
10. When is a water quality treatment facility required?
11. What level of water quality treatment is required?
12. Are stormwater low impact development (LID) techniques required in Kirkland?
13. Are amended soils required in Kirkland?
1. Which surface water manuals are used by the City of Kirkland?
- As of January 1, 2010, Kirkland phased out the old stormwater design manual (1998 King County Surface Water Design Manual). Development projects are now reviewed based on the 2009 King County Surface Water Design Manual and the Kirkland Addendum. The Addendum clarifies requirements that are specific to Kirkland and may be different from the King County manual.
A vesting worksheet is available to determine which manual your project should use.
2009 King County Surface Water Design Manual
Kirkland Addendum to the 2009 King County Surface Water Design Manual.
- Surface water standard details and low impact develoment (LID) design criteria are located in the COK PW Pre-Approved Plans and the 2009 King County Surface Water Design Manual.
2. Where are the stormwater standard details?
The stormwater standard details are located in the PW Pre-Approved Plans. These standards are usually updated once per year.
3. What are the classifications of drainage reviews and what are the requirements?
The types of drainage reviews in Kirkland are:
Small Project Drainage Review - Types I and II
Targeted Project Drainage Review
Full Project Drainage Review
The drainage requirements will vary depending on project and site characteristics. See PW Pre-Approved Plans Policies D-2 and D-3 for classification descriptions and storm requirement details.
Drainage Reports are now required for most projects (except Small Project Type I). Below are Drainage Report Summaries and Templates for applicants to use:
4. How do I find out if there are existing drainage problems downstream from a potential project?
Fill out Drainage & Water Quality Problem Report Form. Mark the Level 1 Analysis box under Nature of Problem.
5. When is a Construction Stormwater General Permit required?
Projects that disturb greater than one acre are required to obtain a Construction Stormwater General Permit from Washington State Dept. of Ecology.
6. When is a Stormwater Pollution Prevention & Spill (SWPPS) Plan required?
For all project sites 1 acre or larger, a SWPPS Plan must be kept on site during all phases of construction and shall address construction-related pollution generating activities. Follow the guidelines in the 2009 KCSWDM, section 2.3.1.4. A SWPPS Plan consists of the following three elements:
- A site plan showing the location and description of BMPs required to prevent pollution and control spills from construction activities and from chemical and other materials used and stored on the construction site.
- A pollution prevention report listing the potential sources of pollution an identifying the operational, source control, and treatment BMPs necessary to prevent/mitigate pollution from these sources.
- A spill prevention and cleanup report describing the procedures and BMPs for spill prevention and including provisions for cleanup of spills should they occur.
See Policy D-12 for guidance on SWPPS Plan.
7. What temporary erosion control is required during construction in Kirkland?
All projects are required to submit an Erosion and Sediment Control (ESC) Plan and ESC Report, and designate an ESC Supervisor. Refer to section 2.3.1.3 in the 2009 King County Surface Water Design manual for general ESC requirements. For project sites 1 acre or larger, a Construction Stormwater Pollution Prevention Plan (SWPPP) is required, as part of the Construction Stormwater General Permit from Washington State Dept. of Ecology.
8. When is a stormwater detention facility required?
Typically, a detention facility is required for projects containing 10,000 square feet or greater impervious surface area in the developed condition. A few exemptions exist and can be found in the King County Surface Water Design Manual Section 1.2.3.
9. What level of flow control is required in Kirkland?
The levels of flow control used in the City of Kirkland are level 1 and level 2. The level is determined by the location of the site and its relationship to sensitive areas. Please refer to the flow control map or contact surface water staff at srush@kirklandwa.gov or 425-587-3800 for help determining the level of flow control for a development project. Projects in level 1 flow control areas can use existing site conditions for pre-developed modeling, but projects in level 2 flow control areas must use historic "forested" conditions for pre-developed modeling when determining detention volumes.
10. When is a water quality treatment facility required?
Typically, a water quality treatment facility is required for projects with 5,000 square feet or more pollution generating impervious surface area (e.g., roads, parking lots, driveways, etc.) in the developed condition. A few exemptions exist and can be found in the King County Surface Water Design Manual Section 1.2.8.
11. What level of water quality treatment facility is required?
Basic water quality treatment is required for single family residential development in Kirkland. Enhanced basic water quality treatment is required for projects one acre or larger in size with the following land uses: multi-family residential, commercial, industrial, and high volume roads (7,500 ADT). For projects less than one acre in size meeting the land use criteria for enhanced water quality treatment, apply the enhanced treatment requirement unless it can be shown as not feasible.
12. Are stormwater low impact development (LID) techniques required in Kirkland?
Stormwater LID is required as feasible in development projects in Kirkland. Applicants are required to evaluate the feasibility and applicability of dispersion and infiltration on all projects. At least one LID technique is required on each project. The City encourages applicants to incorporate bio-infiltration/rain gardens, pervious pavements, and additional landscaping into project development when feasible. LID techniques should be designed according to the PW Pre-Approved Plans and the 2009 King County Surface Water Design Manual.
The policy below is designed to help applicants with this requirement:
Contact surface water staff at srush@kirklandwa.gov or 425-587-3800 for questions regarding surface water LID.
13. Are amended soils required in Kirkland?
Projects sites that are 1 acre or greater, and add 2,000 ft2 or more new impervious area or have land disturbing activity involving 7,000 ft2 or greater, are required to add amended soil to the landscaped areas (follow Ecology's BMP T5.13, per Minimum Requirement #5: On-site Stormwater Management). This includes mixing 2-3" of compost with organic matter into the upper 8" topsoil layer, and loosen 4" of the subsoil. The permit applicant must provide original delivery tickets for all soil and mulch products, and the soil and mulch contents must meet the content ratios stated in BMP T5.13. See Amended Soil Requirements document for more information.