Seattle Green Factor Becomes Law

Seattle Mayor Greg Nickels has signed legislation that will increase landscaping requirements in the city, in part to reduce runoff. It incorporates the new Seattle Green Factor (SGF) which promotes tree planting, garden walls, and green roofs.

Created by the Seattle Department of Planning and Development, the Green Factor applies to new development in neighborhood business districts.

It encourages the planting of layers of vegetation and larger trees in areas visible to the public and in the public rights-of-way adjacent to developments.

There are additional bonuses for using rainwater harvesting and/or low-water-use plantings.

Under the legislation, all new multifamily buildings in a neighborhood business district must have 30 percent of their parcel landscaped with trees, bushes, vines on trellises, or green roofs. The vegetation will help with water quality and replenish groundwater.

When a new project is proposed for development in Seattle's commercially zoned areas, applicants must demonstrate how they intend to meet the new landscaping requirement.

An electronic worksheet available on the Internet helps applicants calculate their score. The worksheet keeps a running score so applicants can test different landscaping arrangements to meet the requirement.

SGF could help meet environmentalists' requests for standards that encourage storm-water management features, including trees in city neighborhoods.

But the Seattle Planning Commission has raised concerns about impacts on small businesses and raises questions about SGF implementation. Critics say vegetation could be a haven for rodents, and in rainy Seattle the storm-water system will still overflow during heavy rain events.