Due to the Vashon Glacial Till (clay) covering 17 feet (after the top soil) of Sunset Hill, we believe these Raingardens will not produce desired results and may possibly exacerbate the Combined Sewer Overflow (CSO).
“Retro-fitted” Raingardens include under-drains underneath the landscaping—an experimental technology that produces disputed data and puts the worth of this type of Raingarden into doubt. SPU has not yet provided data that would demonstrate this as the optimal solution.
Given the cost, inefficiency, and hazards, Raingardens (the Natural Drainage project) lack the return on investment the community is looking for.
Ideally, SPU would work closely with the Ballard community in coming up with CSO solutions that are environmentally effective and cost effective.
Following are other CSO solutions presented to SPU by the Ballard District Council on 10/15/12:
- Educating residents about conserving water and other steps that they can take to reduce combined sewer overflows;
- Expansion of RainWise program for residents, churches, and businesses;
- Small storage solutions, such as under traffic circles;
- Cisterns; and
- “Live storage” options where appropriate.