Low Impact Development - Accomplishments

Project Outcomes

Outcomes of the Low Impact Development code updates include:

1. On January 17, 2016, Council Bill 118523 took effect amending the Land Use Code to remove barriers to low impact development and help make it the standard approach to stormwater management in Seattle.
2. We also updated the City’s Landscape Director’s Rule, DDR 30-2015 (formerly DR 10-2011) which helps interpret landscape requirements for new development. Our proposed updates align the rule with the City’s new Stormwater Code, and further encourage use of Low Impact Development (LID) stormwater management techniques.

The updated regulations and Director’s Rule help the City comply with our municipal stormwater permit requirements and support the City’s goals for on-site management of stormwater.

These updates make it easier to achieve low impact development. We will also encourage LID techniques as part of standard development projects. By treating stormwater close to its source, we can:

• Reduce environmental impacts
• Prevent erosion
• Protect water quality
• Preserve wildlife habitat
• Decrease infrastructure costs

Key Milestones

• June 30, 2015
  Release State Environmental Policy Act (SEPA) Review Draft
• November 2015
  Mayor's Proposed Legislation
• December 3, 2015
  City Council held a public hearing about the proposed regulations
• January 17, 2016
  Final City Council Approval

Project Purpose

We reviewed all land development rules and identified for removal barriers to low impact development and to add provisions to encourage LID where appropriate.

LID 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. Our rule and code updates meet requirements of our municipal stormwater permit from the Washington State Department of Ecology.

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.