A policy roadmap for low impact development in Spokane, Washington

Elise Lebarron

In the process of urban development, much of a site’s vegetation may be removed and its soil impacted o covered with impervious roadways and buildings. These changes alter the hydrologic cycle, generating more runoff containing higher pollutant concentrations than occurred under pre-development conditions. Conventional stormwater management can exacerbate the situation by concentrating runoff into channels and pipes, which increases its flow rate. This generates runoff with greater erosive force that damages aquatic habitat. Stormwater pollutants also contribute habitat degradation and water quality unsuitable for human uses. As a result of the urban stormwater’s environmental impacts, federal and state environmental regulations now require more stringent stormwater controls. Technical approaches are an option, but are costly. Low impact development (LID) is an emerging alternative. This approach strives to emulate a site’s pre-development hydrologic function to prevent environmental impacts normally associated with runoff. In practice. LID combines natural hydrologic processes and site-specific design approaches to minimize runoff volume, rate, and pollutant concentrations. Federal and state agencies actively encourage LID for stormwater management; unfortunately, several barriers may prevent successful LID implementation at the local level. Developers, contractors, and inspectors may lack understanding and technical guidance for proper LID design, construction, and maintenance. Zoning and development codes may discourage and prohibit LID strategies. Like other urban areas, Spokane, Washington is experiencing stormwater challenges and is obliged to address new stormwater regulations. This thesis investigates how can be implemented in the City of Spokane. An overview of LID establishes recommended design, construction, and maintenance approaches and reveals potential regulatory barriers. A review of federal and state environmental regulations and reports from local environmental investigations shows specific ways LID can support Spokane’s regulatory and environmental concerns. Local policy, regulations and technical guidance documents are then analyzed to determine if they support LID implementation. Where contradicts and weaknesses are identified, recommendations are offered that the City of Spokane should consider in its efforts to revise local stormwater management approaches.

A policy roadmap for low impact development in Spokane, Washington

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