"Green Street" natural Drainage Design Case Study

Environmental WORKS and our team at Barker Landscape Architects and Springline Design have created a Green Stormwater Infrastructure case study which built upon a current housing design project in Seattle’s Capitol Hill neighborhood at 12th and Jefferson to explore the feasibility, challenges and opportunities of incorporating natural drainage strategies in the right-of-way at 12th Avenue  to inform future retrofits and development in the area of study and to serve as an informative exploration for similar conditions.

Goals:  Reduce amount of polluted runoff and combined sewer overflow, restore vegetative environment, enhance pedestrian environment.

Objectives:  Improve water quality, provide up to 100% storm water infiltration on-site (need specific soils analysis to determine)

Outcomes:  Create recommendations that add value to Design Guidelines for 12thAvenue.  Create design concepts with input from community and city as available.  Identify synergies and potential application to future 12th Ave projectsLeverage opportunity to expand scope of construction project to also include ROW retrofits.

And what timing!  Look at what else is going on in Capitol Hill:

  • Seattle University’s 12th Ave and James Court Park and Woonerf
  • 12th Ave Pedestrian Safety Study (Dept of Neighborhoods grant)
  • Capitol Hill EcoDistrict
  • Yesler Terrace Redevelopment

Case Study Project Areas –

  1. Alder Street crossing: 12th ave slopes down to the south making water catchment a challenge.  There are no traffic lights, stop signs or pedestrian crossings between Jefferson and Yesler.  A retrofit of one or more intersections with crosswalk provides an opportunity for safe crossing, natural drainage, and flow reduction:  Opportunity to incorporate mid-block curb bulb, curb bulbs, and porous sidewalk.
  2. Olive Intersection through Howell Intersection:  These two intersections are heavily traveled and include Seattle Central College students, however there are no designated crossings:  Opportunity to incorporate curb bulbs and bioretention planters.

Other (future funding) project opportunities:

Fir Street to Yesler: The Yesler Terrace project includes one block of 12th.  Scope of this work could be expanded. Residents in this area have commented about basement flooding and street flooding during heavy rains.

These concepts combine a few different community goals and concerns we’ve heard from the 12th Ave Stewards Committee:  pedestrian safety, aesthetics, stormwater control, and sustainability.

More explorations to come!