Green Infrastructure Digest

Green Street Curb Extension at SE 12th and Clay
(Gateway to the Clay Street green connector)
Source: City of Portland, Environmental Services ©2009

The following is the second part of an email interview I recently conducted with Emily Hauth, project manager with Portland Bureau of Environmental Services (BES)’s Sustainable Stormwater Management Division. Their agency has been a leader in sustainable stormwater implmentation over the last twenty years. She would like to credit Tim Kurtz, engineer at BES with the following responses.

Green Infrastructure Digest (GrID): What role do green streets play in the City’s overall stormwater management strategy, particularly their role in addressing stormwater overflows in your CSO districts as compared to the big pipe projects (i.e. Columbia Slough Big Pipe, East Side Big Pipe, West Side Big Pipe)? What lessons have you learned over the course of implementing your green streets projects?

Mr. Tim Kurtz: Our CSO control program began in 1991. We are completing construction of our third large CSO tunnel to help us complete the program by the mandated deadline of 2011. But several projects to reduce CSO volume by removing stormwater from the combined sewer system are very important to the CSO control effort. For example, we have disconnected thousands of downspouts from the combined sewer system since 1995. It’s a relatively low-cost CSO solution but it’s a major part of our green infrastructure. Downspout disconnections remove more than 1.2-billion gallons of stormwater annually from the combined sewer system.

Green streets will play an important role in ensuring that our new CSO tunnels remain under capacity as new growth and development increase stormwater volume in the future.

Green streets also help alleviate basement flooding from sewer backups in neighborhoods with combined sewers; they are a good alternative to sumps and sedimentation manholes, and they are an important tool in meeting water quality requirements in Portland’s urban streams.

We use Green Streets and other stormwater management facilities to meet different needs such as improved water quality, flow control, and complete infiltration. We’ve learned that soils can be a determining factor in how our facilities are constructed to meet our different goals. On Portland’s east side, soils typically meet our infiltration rates (>= 2 “per hour) but often require underground rock storage to meet complete disposal goals. On the city’s west side, where soils are much tighter, we typically line facilities to meet water quality goals.

Monitoring green street function has been important in proving that they work and that green infrastructure makes good fiscal sense. In the 2.5 square mile Tabor to the River Program area, green streets save us money. The original estimate using traditional grey infrastructure was $144 million in today’s dollars. Two years later, the program was re-designed with a combination of grey and green infrastructure. The current estimate for this integrated approach is $81 million. Through monitoring we’ve also evaluated and modified design components to improve function. We’ve realized economies of scale with larger project areas. We’ve also created guidelines for green street construction practices, recognizing that incorrect soil types and compacted soils can hinder green street function

GrID: With the recent Portland Tribune article regarding the 44th Avenue and Seymour Street Green Street Project, what is your process for implementing a green street project? To what extent do you involve the public in the design/location of the facilities?

Mr. Kurtz: The outreach process for green street implementation always includes property owners affected by a green street facility. With all projects, we meet with adjacent property owners, attend neighborhood and business association meetings, offer presentations to groups, distribute informational publications and host green street tours.

• At 30% design, the city sends information to adjacent residents for small projects or all project area residents for larger projects.
• At 90% design, the city mails notification to all project area residents of upcoming construction.
• Depending on project needs and priority, there may be flexibility in facility type and location. But the city determines the final design to meet system needs.
• Adjacent property owners can choose from a set of planting templates, with the opportunity for some customization.

The public has responded positively to this hands-on approach to explain the benefits and cost savings of green streets. More than 100 citizens have called to ask the city to install a green street facility next to their homes. Of course, not all property owners are supportive, as is the case along SW 44th and Seymour. We view this public process also as an opportunity to receive feedback, both negative and positive, and work to address the issues.

Back to Part 1

Part 3-Monday

Flow Test Monitoring of Green Street in Portland
Source: City of Portland, Environmental Services ©2009

-Brian Phelps