Proposed Updates to Stormwater Management Strategies

DPD transmitted legislation to City Council that proposes to amend the Land Use Code to encourage Low Impact Development (LID), a stormwater management strategy that mimics natural processes to reduce the amount of rainwater that runs off a site. LID strategies include bioretention, reducing impervious surfaces, and clustering buildings together to reduce site disturbance. In September 2015, DPD completed the SEPA review of the proposed legislation.

In undeveloped areas, most precipitation soaks into the ground, evaporates, and/or is absorbed by plants, and very little rainfall becomes surface runoff. Developed areas with pavement and rooftops have much more runoff, less infiltration, water quality challenges, and greater fluctuation in stream and lake levels. DPD has reviewed all land development rules and has proposed code amendments to remove barriers to LID. These amendments are a requirement of the City’s municipal stormwater permit from the Washington State Department of Ecology.

Our proposed code changes will make it easier to incorporate LID strategies into a broad range of development types. The changes include modifying existing language to allow implementation of LID, listing LID as a public benefit item, and broadening definitions to include LID. None of the changes requires an applicant to implement any particular strategy; the Stormwater Code is the regulatory document containing stormwater management requirements.

The City Council is expected to introduce the legislation in late November.

Questions?

Nick Welch
(206) 684-8203
nicolas.welch@seattle.gov

Maggie Glowacki
(206) 386-4036
margaret.glowacki@seattle.gov

Proposed Updates to Stormwater Management Strategies

DPD transmitted legislation to City Council that proposes to amend the Land Use Code to encourage Low Impact Development (LID), a stormwater management strategy that mimics natural processes to reduce the amount of rainwater that runs off a site. LID strategies include bioretention, reducing impervious surfaces, and clustering buildings together to reduce site disturbance. In September 2015, DPD completed the SEPA review of the proposed legislation.

In undeveloped areas, most precipitation soaks into the ground, evaporates, and/or is absorbed by plants, and very little rainfall becomes surface runoff. Developed areas with pavement and rooftops have much more runoff, less infiltration, water quality challenges, and greater fluctuation in stream and lake levels. DPD has reviewed all land development rules and has proposed code amendments to remove barriers to LID. These amendments are a requirement of the City’s municipal stormwater permit from the Washington State Department of Ecology.

Our proposed code changes will make it easier to incorporate LID strategies into a broad range of development types. The changes include modifying existing language to allow implementation of LID, listing LID as a public benefit item, and broadening definitions to include LID. None of the changes requires an applicant to implement any particular strategy; the Stormwater Code is the regulatory document containing stormwater management requirements.

The City Council is expected to introduce the legislation in late November.

Questions?

Nick Welch
(206) 684-8203
nicolas.welch@seattle.gov

Maggie Glowacki
(206) 386-4036
margaret.glowacki@seattle.gov

SEPA Decision for Low Impact Development Code Changes

DPD has completed the SEPA review of the proposed low impact development (LID) code changes. DPD has also updated the LID website has been updated to include links to the LID ordinance/code amendments, Director’s Report, SEPA Decision, and the SEPA Checklist.

Low impact development is a stormwater management strategy that mimics natural processes to reduce the amount of rainwater that runs off a site. LID strategies include bioretention (a process that removes contaminants from stormwater), reducing impervious surfaces, or clustering buildings together to reduce site disturbance.

In undeveloped areas, most precipitation soaks into the ground, evaporates, and/or is absorbed by plants, and very little rainfall becomes surface runoff. The natural water cycle relies on plants and infiltration to manage stormwater, replenish groundwater, and maintain water levels in streams and rivers. Developed areas with pavement and rooftops have much more runoff, less infiltration, higher risk of flooding and water quality issues, and greater fluctuation in stream and lake levels.

DPD has reviewed all land development rules and has proposed code amendments to remove any barriers to low impact development and to encourage LID where appropriate. These amendments are a requirement of the City’s municipal stormwater permit from the Washington State Department of Ecology.

Our proposed amendments increase flexibility for certain low impact development strategies in a broad range of zones and development types. They generally fall into one of two categories:

  • Modify existing language to remove barriers to implementing low impact development (e.g., landscaped areas must be protected, not enclosed by a curb or barrier)
  • Encourage low impact development by listing it as a public benefit item or broadening a term to include LID strategies (e.g., allowing bioretention to count towards amenity area requirements)

Currently, property owners can install cisterns in yards and setbacks, where appropriate. Our proposal also makes it clear that applicants can install features like rain gardens and other green stormwater infrastructure features where landscaping is required, such as in surface parking lots and residential or commercial amenity areas. As these low impact development strategies become more common and familiar, it is important the City’s land use regulations do not inadvertently prohibit this best practice.

None of our proposed changes require an applicant to implement low impact development. The Stormwater Code is the regulatory document that outlines stormwater management requirements. Furthermore, the proposed amendments do not prohibit any action or development that is currently permitted under the Code. Our proposed amendments support the City goals for managing stormwater with green stormwater infrastructure.

If you have questions regarding the proposed LID code amendments please contact:

Maggie Glowacki
(206) 386-4036
margaret.glowacki@seattle.gov

Nick Welch
(206) 684-8203
nicolas.welch@seattle.gov