Green Infrastructure

Precipitation that reaches hard ground surfaces becomes stormwater runoff, and this runoff has the potential to create flooding and contaminate downstream Waters of the State. As it flows over ground surfaces like roadways and parking lots, stormwater runoff picks up contaminants and can carry the pollutants with it as it makes its way to either the river or the aquifer. Stormwater runoff that is managed properly relieves downstream flooding, and minimizes or eliminates stormwater pollution from reaching the river and/or aquifer. Stormwater Best Management Practices (BMPs) are utilized to manage runoff by capturing, cleaning, and sometimes infiltrating stormwater as near to its’ point of origin as possible, which is done in order to minimize the amount of pollution generated, as well as to maintain the natural downstream hydrology.

Development, or re-development, of land can be performed in ways that retain, or create, green spaces for the purpose of managing stormwater as close to its source as possible. This approach is called Low Impact Development (LID), and it uses natural tools, such as healthy vegetation, permeable ground surfaces, and good soils to treat and reduce stormwater flows to the conveyance systems and surface waters. In Spokane, LID approaches are generally employed when planning and designing for stormwater treatment areas, where the BMPS are designed in accordance with the principles provided in the Spokane Regional Stormwater Manual (SRSM). Olmsted Brothers Green in Kendall Yards, Hazels Creek, Sharp Avenue permeable pavements, and the roadside bioretention features installed on East Indiana Avenue near Ruby Street, and South Lincoln Street are examples of low impact development.

A stormwater management area that is developed using LID approaches and designed in accordance with the SRSM is considered Green Stormwater Infrastructure (GSI).  GSI uses nature’s tools and natural processes within engineered systems to manage stormwater in ways that mimic natural hydrologic conditions.  It is a cost-effective and resilient approach to managing stormwater with infrastructure that delivers environmental, social, and economic benefits, and results in healthier urban environments. In practical terms, GSI generally takes the form of landscaped green areas that receive stormwater runoff from streets and developed lots, and retain it until it soaks into the soil. The use of low-impact development techniques to create green stormwater infrastructure is one strategy to protect our river and aquifer, and enhance the quality of life in our neighborhoods.

In the City of Spokane, GSI exists as a patchwork of green areas that are designed to manage stormwater by using healthy vegetation and soils in recessed areas to temporarily store, infiltrate, and ultimately treat runoff from rain events.

GSI areas used to manage stormwater must be maintained to ensure they are performing optimally by receiving and treating the stormwater runoff they were designed for. Responsibility for maintenance of green areas can be private or public, or a combination of both, dependent on where the area resides and the stormwater service it is providing. In order to meet the desired performance needs, green areas must be able to accept stormwater runoff, maintain healthy vegetation, and have enough capacity to temporarily store the stormwater until it soaks into the ground or discharged to an infiltration facility or receiving water body. Detailed information on the maintenance stormwater treatment areas is provided within the pamphlet Managing Stormwater – A Residential Guide. Ultimately, in order to keep a green stormwater treatment area maintained, three basic tasks should be performed:

  1. Clear inlets
  2. Remove sediment and debris
  3. Keep vegetation healthy

Information on green area maintenance in the City of Spokane is provided in the Green Area Maintenance video below.

Learn more about low-impact development:

Working with The Lands Council

The City of Spokane and The Lands Council, a local nonprofit, have partnered to bring information to citizens about green stormwater management and the benefits of such facilities.

The City contracted with The Lands Council to reach out to neighborhood residents and businesses to talk about stormwater and the benefits of using green strategies, including "storm gardens." Outreach has occurred in both the Chief Garry Park and Shadle Park neighborhoods.

Additionally, in the Shadle Park neighborhood, The Lands Council and the City partnered on a pilot project to add a few storm gardens in the Shadle Park neighborhood. The Shadle Park Neighborhood was selected because it is part of a combined sewer area that's a good candidate for green technologies because of its smaller size and better, free-draining soils.

The Lands Council worked to identify property owners interested in having a garden installed to capture stormwater and filter it on site. The gardens include native plants and special soils, including a layer of biochar, a charcoal-like material that is a by-product of biomass facilities.

This outreach is part of the City's work under its Integrated Clean Water Plan to manage stormwater and wastewater that impacts the Spokane River. The integrated plan prioritizes projects based on their positive environmental impact to the river. It includes projects to reduce untreated discharges to the river from both separated storm sewers and combined sanitary and stormwater sewers. One of the goals of the plan is to incorporate new cost-effective, green technologies for managing stormwater on site and reducing the amount of water flowing into pipes that discharge directly to the river.

For more information, visit The Lands Council.