Connecting actions to ecological and human health endpoints - evaluating the benefits of wastewater and stormwater projects

Local wastewater and stormwater utilities invest millions to billions of dollars collected from ratepayers to meet regulatory requirements, protect human life and infrastructure, and protect water quality. In their project prioritization and planning efforts, utilities consider many factors, including the benefit to environmental outcomes. Utilities often compare the environmental benefits of potential projects by only evaluating changes in pollutant loads rather than looking at whether those projects will accomplish better environmental outcomes for people and wildlife. Many utilities lack a framework for considering these ultimate outcomes. In an effort for better-informed decision-making in King County, WA, we developed a framework (the Water Quality Benefits Evaluation toolkit) that connects actions to environmental outcomes.

The toolkit is an adaptable framework containing a watershed pollutant loading model, a pollutant-reduction and cost optimization model, and causal models representing systems surrounding specified environmental outcomes. We developed causal models for six endpoints: toxics in edible fish, fecal contamination at shellfish beds, fecal contamination at swimming beaches, algal toxins at swimming beaches, natural-origin Chinook salmon population health, and Southern Resident Killer Whale population health. The causal models include Bayesian networks, narrative conceptual models, and fish bioaccumulation models. The holistic evaluation of environmental outcomes provides better information to decision-makers to consider alongside other factors such as costs to ratepayers and reversing environmental inequities.

This presentation focuses on the development of the causal models and how they can be applied to support King County’s utility planning decisions. The presentation will also provide insight on how the framework can be employed for additional environmental endpoints and may be adapted to include other types of endpoints, such as equity and community health.