Refer to the 2011 Addendum for more specific information.
The default design standard for water quality treatment is Senstive Lake Protection (phosphorus control). Other design standards, including Basic, Enhanced Basic, and Oil Control, may also apply depending on the proposed land use and whether infiltration is proposed.
The City will permit treatment facilities that are contained in any technical manual approved by Ecology (i.e., King County, Ecology and WSDOT), as well as new BMPs that meet or are being tested under Ecology's Emerging Stormwater Treatment Technologies program.
Temporary Erosion and Sediment Control (TESC) permit coverage is required for all land disturbing activities (with some exceptions). TESC requirements are addressed in the Public Works permit for the project, typically a clearing and grading permit. For smaller projects that don't trigger a clearing and grading permit, a separate Public Works permit for TESC will be required.
A 100 NTU turbidity discharge limit is effective year-round, until the project is permanently stabilized.
Plan submittal requirements are revised to follow the 2011 Addendum. Designated TESC supervisors shall be a Certified Erosion and Sediment Control Lead (CESCL).
Note: A separate Department of Ecology Construction Stormwater General Permit is required for sites having 1 acre or more of disturbed area.
Stormwater Low Impact Development (LID)
Stormwater LID is required in areas of the City that are favorable for infiltration (e.g., outwash and alluvial soils). In those areas, stormwater infiltration or LID techniques must be used, unless soil testing data shows the soil is unsuitable. See Special Requirement #6 in the 2011 Addendum for details. The City's stormwater code also allows for deviations from standards to allow Low Impact Development designs, such as narrower street widths and use of pervious pavement.
Kerry Ritland, PESurface Water ManagerEmail425-837-3410