FAQs regarding the Revised Stormwater Regulations:
- What are the revised stormwater regulations?
- Why are the changes needed?
- When will the revised regulations go into effect?
- What are the change to flow control requirements?
- What are the changes to water quality treatment requirements?
- Is LID required in Kirkland?
- What is the new soil amendment requirement?
- What are the new Erosion Control requirements?
- What is a Stormwater Pollution Prevention and Spill (SWPPS) Plan?
1. What are the revised stormwater regulations?
The Washington State Department of Ecology issued the Western WA Phase II Municipal Stormwater Permit on February 16, 2007 under authority delegated to it by the US Environmental Protection Agency, pursuant to the Federal Clean Water Act. The permit requires Kirkland to adopt certain alterations to surface and stormwater portions of the Kirkland Municipal Code, and to adopt revised development regulations equivalent to the 2005 Ecology Stormwater Management Manual for Western WA.
The key change is the Adoption of a New Development Stormwater Manual
The City of Kirkland has adopted the following documents for development in Kirkland:
Development proposals must meet all requirements in the above documents. The 1998 King County Surface Water Design Manual will only be used on projects that are vested prior to 01/01/2010. Below are several documents to help with permit submittals.
2. Why are the changes needed?
Kirkland must seek coverage under the Western WA Phase II Municipal Stormwater Permit, or face third party lawsuits, fines, or other penalties under the Federal Clean Water Act. The changes are required for permit compliance. The full permit can be viewed at the Department of Ecology's website.
3. When will the revised regulations go into effect?
The new design requirements are effective January 1, 2010.
4. What are the changes to flow control requirements?
Flow control will no longer be based just on new impervious surface area; it will be based on "target impervious surface" which is a combination of a site's existing, new, and replaced impervious surface. See the 2009 KCSWDM for specific flow control requirements and exemptions. Projects in Level 1 flow control areas can use existing site conditions for pre-developed conditions, but projects in Level 2 flow control areas must use "forested" conditions as the pre-developed conditions when determining detention size.
COK Flow Control Map to determine the level of flow control for your project.
5. What are the changes to water quality treatment requirements?
The threshold for a water quality treatment system remains 5,000 ft2 pollution generating impervious surface area (PGIS), but it is based on “effective” PGIS (both new and existing PGIS if the drainage surfaces are connected), not just the new PGIS.
In addition, the level of water quality treatment has changed for certain land uses. Multi-family residential, commercial, and industrial project sites one acre or larger (and high ADT roads) may be required to provide enhanced water quality treatment that targets the removal of metals (such as copper and zinc). Below is a link to a list of enhanced treatment facilities approved by Ecology:
6. Is LID required in Kirkland?
Stormwater low impact development (LID) is required as feasible on 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. The policy below is designed to help applicants with this requirement:
7. What is the new soil amendment requirement?
Project sites that are one acre or greater, and add 2,000 ft2 or more new impervious area or have land disturbing activity involving at least 7,000 ft2 or greater, are required to add amended soil to the landscaped areas (follow Ecology 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.
8. What are the new Erosion Control requirements?
All projects must comply with all nine construction elements, designate an Erosion and Sediment Control (ESC) supervisor, and submit an ESC Plan and ESC Report. For project sites 1 acre or larger, a Construction Storm Water Pollution Prevention Plan (SWPPP) is required, as part of the Construction Stormwater General Permit from Washington State Dept of Ecology. Turbidity monitoring is required if project contains a lake, stream, or wetland and is 1 acre or larger. Refer to the 2009 King County Surface Water Design Manual for specific erosion control requirements.
9. What is a Storm Water Pollution Prevention and Spill (SWPPS) Plan?
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 King County Surface Water Design Manual. 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 and 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 clean-up of spills should they occur.
See Policy D-12 for guidance on a SWPPS Plan.