Integrated Planning and Water Quality Benefits in Seattle, WA
The City of Seattle, Seattle Public Utilities (SPU), the U.S. Environmental Protection Agency (EPA), the U.S. Department of Justice (DOJ), and the Washington State Department of Ecology (ECY) have negotiated a Consent Decree that establishes requirements for SPU’s Combined Sewer Overflow (CSO) Reduction Program. The Consent Decree allows SPU to propose an Integrated Plan for implementing stormwater control projects in addition to CSO control measures outlined in a Long Term Control Plan. Development of an Integrated Plan provides the opportunity to propose stormwater and CSO project actions, prioritized and sequenced in order to achieve greater benefits for water quality of the receiving waters in and around Seattle than would otherwise be achieved with CSO investments alone. Seattle is one of the first cities in the country to have the opportunity to demonstrate an integrated and prioritized program of stormwater and CSO projects as part of a Consent Decree.
To develop the Integrated Plan, SPU first ranked its receiving water bodies based on the Consent Decree requirements. Next, SPU developed preliminary loads and cost estimates to identify potential stormwater projects to be implemented and CSO projects to be deferred. The CSO deferral candidates are detention projects while the candidate stormwater projects include a mix of green, gray, and programmatic measures.
SPU developed pollutant loads models and conducted exposure assessments to compare the water quality, human health and habitat benefits of each stormwater and CSO project, as required by the Consent Decree. SPU used multi-objective decision analysis (MODA) to help select the combination of stormwater projects and CSO deferrals that meets the Consent Decree requirements and supports SPUs triple bottom line decision making-- financial, environmental and social impacts and benefits. SPU assembled an independent Expert Panel to review and help refine the analytical methods and provide feedback on the results.
The option to propose an Integrated Plan as part of the Long Term Control Plan provides SPU with the opportunity to demonstrate the value of a more integrated approach for improved water quality that will result in larger improvements in wet weather discharges than would have occurred without the integrated approach.
This paper will present an overview of the process, some of the technical challenges and how they were overcome, and the resulting integrated plan. Key take-aways include the peer review process and how stormwater projects were compared to CSO projects to identify “significant water quality benefits” and how the concepts of integrated planning applied in this project may be applicable to watershed planning and project prioritization to meet multiple objectives in California. The authors will engage the audience by asking a few key questions for feedback and then compare to what happened in the actual project.