Planning, Development & Construction Resources

Are you developing in the City of Sammamish? If you are applying for a land use permit, building permit, or clearing and grading permit, drainage review may be required.

When is Drainage Review Required?

Pursuant to SMC 13, the 2016 King County Surface Water Design Manual, and the City of Sammamish Addendum to the 2016 King County Surface Water Design Manual, drainage review is required when:

  1. The project adds or will result in 2,000 square feet or more of new impervious surface, replaced impervious surface, or new plus replaced impervious surface, OR
  2. The project proposes 7,000 square feet or more of land disturbing activity, OR
  3. The project proposes to construct or modify a drainage pipe/ditch that is 12 inches or more in size/depth, or receives storm water runoff or surface water from a drainage pipe/ditch that is 12 inches or more in size/depth, OR
  4. The project contains or is adjacent to a flood hazard area as defined in KCC 21A.06, OR
  5. The project is located within a Critical Drainage Area, OR
  6. The project is a redevelopment project proposing $100,000 or more of improvements to an existing high-use site, OR
  7. Projects located in a landslide hazard drainage area that will result in 500 square feet or more of new impervious surface, OR
  8. Projects as listed in SMC 13.20.020.
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Links to Stormwater Codes and Design Requirements

CITY STORMWATER CODES

SURFACE WATER DESIGN REQUIREMENTS FOR PROJECT APPLICATIONS SUBMITTED AFTER JANUARY 1, 2017

If you have submitted an application for a project after January 1, 2017, or if you have submitted a subdivision application before January 1, 2017, but start construction after January 1, 2022 the following surface water design requirements apply:

See the Maps and GIS Data webpage for mapped flow control, water quality, landslide hazard drainage and erosion hazard areas as they relate to these requirements.

FORMS

SURFACE WATER DESIGN REQUIREMENTS FOR PROJECT APPLICATIONS SUBMITTED BEFORE JANUARY 1, 2017

If you have submitted an application for a project before January 1, 2017 the following surface water design requirements apply:

See the Maps and GIS Data webpage for mapped flow control, water quality, landslide hazard drainage (pre-2017) and erosion hazard areas as they relate to these requirements.

FORMS

OTHER RESOURCES

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