Conference Agenda

The Northwest has embraced watershed planning for over twenty years as a useful way to prepare for and implement strategies to improve the health of waterways while effectively managing limited budgets and staff resources.

Now, there are new challenges facing watersheds that Parametrix has begun to integrate into watershed planning and will discuss in this presentation.

Parametrix has worked with multiple jurisdictions to develop integrated watershed plans and long-term growth management studies. Parametrix has worked with 20 plus communities on integrated watershed planning from large to small.

As part of our planning process, we will discuss how to address long-term management of existing municipal systems while also plotting courses for future land use development and responsible growth. Parametrix will discuss how to set goals; determine strategies; and define actions and funding strategies for risk management, environmental stewardship, climate change, and compliance with stormwater regulations as the population of a watershed grows.

This presentation will discuss key elements common to integrated watershed planning, including:

- Land use planning that is compatible with watershed protection targets

- Watershed prioritization and identifying key water quality issues within watersheds

- Systems for scoring and ranking needs to prioritize elements within a capital project plan

- Equity and social justice

- Retrofitting and neighborhood redevelopment

- Green infrastructure evaluation and code review

- Solutions to existing flooding problems

- Asset management and prioritization of existing infrastructure

- Managing project milestones to support public-agency grant funding

- Public awareness and involvement

- Utility rate analyses for different funding scenarios and levels of service

Parametrix will also discuss several innovative approaches that have proven successful across these different plans:

- Developing a stormwater management vision and mission, identifying measurable outcomes for each plan element, and discussing risks early on

- Straight-forward ways to address the impacts of climate change in existing design requirements

- Basin-specific water resource protection standards

- Updating development standards, including infill, redevelopment, new site development, and water quality retrofits based on a more integrated understanding of potential impacts

- Use of key habitat-quality metrics to help prioritize protection and development efforts

Nestled within Seattle’s Washington Park Arboretum is the Arboretum Creek, which flows northward into Lake Washington's Union Bay. As with many urban streams, this creek was suffering from the impacts of deforestation, underground piping, urbanization, and flow diversion that started more than 100 years ago. In the 1920s, several hillside springs were diverted into the combined sewer system that ultimately now contribute to historical combined sewer overflows at the Montlake Cut. The nonprofit group Friends of Arboretum Creek (FOAC) has advocated for and led Arboretum Creek restoration efforts for several years. This presentation will share the development of partnerships and plans to restore the natural hydrology of the Arboretum Creek watershed by reconnecting two of the major springs with Arboretum Creek while also addressing localized flooding and treating stormwater runoff from a major arterial. The location of the headwaters is rich with history and community interest, including being an Olmstead Brothers park, the site of UW Arboretum collections and Japanese Gardens as well as a complex array of asset owners to coordinate across. This meant that the design requires close collaboration with partners to achieve not only water quality improvement but also enhance these valuable community resources.

Through funding by King County Wastewater Treatment Division with support and collaboration from the Seattle Parks Foundation, FOAC is developing design plans to collect runoff from the two springs as well as upstream urban runoff and convey the flows to the Arboretum Creek headwaters. These flows will be managed through a treatment train with easy-to-maintain upstream presettling and a subsurface treatment wetland, and ultimately arrive at the creekbed through hyporheic discharge. But wait, there’s more! The treatment wetlands will also be optimized to treat overflows from the adjacent Japanese Garden koi pond to address nutrients reduction. The presentation will highlight elements of the innovative design and summarize the collaboration and funding opportunities with partners to maximize benefits while integrating with the Washington Park vision and enhancing the horticulture collection within the park.