Green Streets Pave the Way to Greener Communities
by Jason A. King, ASLA, and Shawn Kummer


The current dialogue surrounding economic stimulus packages and infrastructure investment needs to expand to include green infrastructure, which provides multiple benefits to our communities. If we merely think of job creation and rebuilding the same failing gray infrastructure as the goals of this new ”New Deal,” we will miss a huge opportunity to regenerate both the structure and the spirit of our cities. Green infrastructure provides a valuable tool for landscape architects, urban designers, and engineers to reframe the distinction between gray and green. This isn’t an either/or debate or a consideration of a luxury item, where we incorporate green only when conditions are right and money is abundant. Instead, it is a redefinition of what works best and costs less. The distinction between gray and green should disappear; the appropriate consideration is, what infrastructure is worthy of investment?

Green streets, like many other green infrastructure strategies, offer the same or better functional contributions as gray streets, as well as a range of added benefits. For example, green storm water design contributes to communities well beyond treating 90% of roadway pollutants, replenishing groundwater, sequestering carbon, and improving air quality. More expansive community benefits include improved neighborhood aesthetics, green connections, pedestrian and bicycle safety, traffic calming, and building community consensus around what is a good infrastructure investment. This transfer of investment from single-purpose gray infrastructure such as cartridge storm filters to multi-purpose green infrastructure investment allows for greater benefit to communities—both financially and environmentally—making every dollar invested pay back abundantly. The economics are simple:  green storm water infrastructure provides more green in our communities, costs less, works better, is easily scalable, and is more resilient and adaptable than standard pipe systems. While the techniques to improve the control and treatment of storm water runoff are still evolving, green stormwater designs, like many other green infrastructure techniques, are proving to be flexible, offering solutions at a variety of scales rather than just at the end of the pipe. 

Through design and policy, the integration of stormwater management into the street right-of-way has evolved from catch basins to roadside grassy swales, to a number of current urban ”green street” examples that allow for parking access, pedestrian movement, furniture zones, street trees, and more. These also give designers the ability to address flows of water and the inner workings of systems within close proximity to users—allowing a reconnection to the cycles of nature that are often obscured in the urban environment. In essence, green streets become great streets.

Two different types of recent projects in Portland, Oregon best express a range of potential green infrastructure and urban designs that capture opportunities and respond to the local context. 102nd Avenue, a heavily travelled arterial in East Portland, incorporates streetscape development, stormwater management, and an artistic gateway feature that is both functional and beautiful. Denver Avenue Streetscape, in the Kenton neighborhood of North Portland, incorporates green strategies to create a vibrant and sustainable local main street shopping district. Together they offer possible solutions to vastly different corners of Portland’s urban environment, and highlight the cooperative efforts of landscape architects, engineers, and urban planners in addressing community and environmental needs.

102nd Avenue District:  Greening the Artery

In February of 2000, Portland City Council and the Portland Development Commission (PDC) approved the Opportunity Gateway Concept Plan and Redevelopment Strategy, and the following year, the Council approved the Gateway Regional Center Urban Renewal Plan, which established the Regional Center as a tax increment district capable of financing up to $164 million for public improvements over 20 years. This district, which sits on the east edge of Portland, had for years struggled to maintain its identity in a place that is neither urban nor suburban. However, its close proximity to two adjacent freeways, light rail connections to regional centers, and the airport, led planners to project that it will eventually become one of the most accessible locations in Portland, thus spurring renewed interest in and redevelopment of the Gateway District.

Typical pedestrian unfriendly conditions along 102nd Avenue prior to construction of planned improvements. Narrow seven foot sidewalks in which utilities were located created obstacles in several locations. Image courtesy GreenWorks, P.C.

In 2003, the 102nd Avenue Streetscape Improvement Project was born from this effort when the green street construction movement in Portland was just beginning to build momentum.  102nd Avenue was targeted for improvements because of its importance as the main north/south arterial spine running through the Gateway District. The project was made possible through a federal transportation funding grant to the Portland Office of Transportation. 102nd Avenue is a very busy 80-foot wide corridor, approximately a mile long, characterized by the predominantly commercial and some residential development that lines it. Narrow seven foot sidewalks filled with utilities and a lack of street trees made 102nd Avenue inhospitable to pedestrians and generally unattractive.

The main goals for the project were to improve the corridor for use by pedestrians, bicyclists, and motorists, and to implement a streetscape design that would enhance the character and identity of the district in such a way as to help encourage and stimulate commercial vitality there. Not lost among the complicated issues was the desire to implement green infrastructure to help promote these goals along with the intrinsic benefits that could be realized from their construction.
The initial phase of the project involved an examination of different options for reconfiguring the travel lanes, parking, and a central median. Given the high volume of traffic on the street, it was decided to retain the existing street width and to increase the width of the sidewalk through property acquisition. Bicycle lanes were created by removing parking on one side of the street and narrowing drive lanes, which was accomplished simply by re-striping existing paving.

Initially, the median, which had been a left turn lane running the entire length of 102nd Avenue, was to become a tree-lined boulevard that would also be utilized for stormwater management. However, this alternative would have required an entire street reconstruction to re-grade the street so stormwater could run to the middle, and it would have restricted access to many of the commercial properties along the corridor. The compromise was to construct a raised median with street trees only in locations that would not limit left hand turning movements. Additional raised medians were constructed at strategic locations to enhance pedestrian access across 102nd Avenue at the midpoint of long blocks that were far from controlled intersections.

Once it was decided that the street section would be divided primarily by the roadway being re-striped, much of the focus of the project turned to improvements within the pedestrian zone. It is here that many of the project goals would be accomplished, particularly in defining a new identity for the district. New elements within this widened zone were pedestrian scale ornamental lighting, street trees with custom grates, and concrete accent paving in the furnishing zone.

Absent from this list in the design phase were green street infrastructure improvements for collection and treatment of stormwater from the roadway and sidewalks within the right of way. However, this was not due to a lack of interest or even resistance to an alternative engineering method to handle storm drainage. Initially, the project was exempt from the requirement to treat stormwater in the right of way because current codes did not provide for such treatment for streets if they were not realigned or the pavement was not removed. However, when the project moved into construction design, there was greater political pressure to add green infrastructure to the project. So, twelve linear stormwater planters were designed into the project prior to going out to bid. These features ultimately provided effective stormwater control and also added green vegetation to soften expansive areas of paving and provide additional traffic buffers for pedestrians.

Improvements on 102nd Avenue show sidewalks widened to fifteen feet where possible, accent paving in the furnishing zone, and stormwater planters for
treatment and infiltration of stormwater from adjacent street and sidewalk paving. Image courtesy GreenWorks, P.C.

The first phase of construction on 102nd Avenue, from NE Weidler to NE Glisan, was completed in January 2009 by Thompson Brothers Excavating Inc. GreenWorks PC (landscape architects) worked with the Portland Department of Transportation (PDOT) and the Portland Development Commission on the streetscape design. David Evans and Associates assisted the City with right of way acquisition and lighting design.

In addition to streetscape improvements made to 102nd Avenue itself, two gateway locations were identified for improvements on the north and south end of the corridor to help cultivate an identity for the district. The north gateway features an artistic kinetic sculptural landmark to make visible the strong winds that characterize this location. The project became known as “Windscape,” featuring a sculptural landform of recycled concrete for low retaining walls that wrap around the site, a stormwater infiltration basin, and vertical “wind poles” that provide a multi-functional landscape that is both a vibrant amenity and  an innovative green infrastructure. The south gateway reclaimed a large triangular shaped area of paving between where the 103rd and 102nd Avenue couplet merge. It features low walls constructed from recycled concrete and planted landscape. A green street stormwater feature could not be achieved at this site due to topographic and site size constraints. 

Stormwater runs off adjacent paved surfaces into stormwater infiltration basin in the foreground, which is integrated into the sculptural landform of walls constructed of recycled concrete, reclaimed from demolition on the project. Flexible red poles that bend in the wind cut through the site. Image courtesy GreenWorks, P.C.

Windscape is a PDOT/Portland Office of Transportation project. GreenWorks was the lead designer on this project, in collaboration with David Evans and Associates (project management, stormwater facility engineering and structural engineering), and Pete Beeman (technical assistance and wind pole feasibility).

Denver Avenue:  Greening Main Street

North Denver Avenue, stretching four blocks from Watts Street to north Interstate Avenue, forms the heart of the historic Kenton Neighborhood commercial district. In the summer of 2006, the PDC assembled a team to design the streetscape that created The Downtown Kenton – Denver Avenue Streetscape Plan in Spring 2008. Besides the PDC, project team members included SERA Architects (planning and urban design), GreenWorks (landscape architecture), PDOT, Landsman Transportation Planning (parking consultant), and Valerie Otani (public art consultant).

The existing eighty foot right of way that forms Denver Avenue has relatively narrow ten foot wide sidewalks with dense canopied street trees that obscure store fronts, a center median, two regular travel lanes, five foot bike lanes, and parking on both sides. The expansiveness of paving encourages drivers to speed through the business district, making the pedestrian environment seem unsafe and uncomfortable. An extensive public involvement process that included regular meetings with a citizen advisory committee, as well as public open houses and workshops sought to meet the needs and desires of local area residents, property owners, and business owners. The primary objectives identified from this process were to make the Denver Avenue streetscape safe for all users, bike- and pedestrian-friendly, attractive, unique, durable, and green. Ultimately, these improvements should promote the revitalization of this historic business district where many properties are underutilized.

Photo above shows current existing condition of the Kenton Neighborhood commercial district in north Portland. The rendering below shows proposed street improvements, featuring green street stormwater planter facilities in the sidewalk furnishing zone. Image above courtesy GreenWorks, P.C.; image below courtesy SERA Architects.

The key design elements in the plan include sidewalks widened to fifteen feet with accent paving in the furnishing zone, new street trees, stormwater planters, widened bicycle lanes, curb extensions at intersections, bike racks, custom designed benches, pedestrian scale ornamental lighting, one foot wide curbs, and public art. A paving technique called “ultra-thin white-topping” will be employed in the roadway, a process which overlays 2-4 inches of concrete designed to bond to existing asphalt or concrete pavement after grinding the surface. Short joint spacing is typical to help improve performance, which will add to the aesthetic character of the paving. A darker concrete mix is also proposed for parking aisles and intersections to provide additional traffic calming as well as to visually break up and add interest to the paving.

Of the proposed streetscape elements, stormwater flow-through planters will provide the strongest visual impacts on the new street. The use of stormwater planters, which will capture and treat stormwater runoff from the adjacent sidewalks and roadway, were proposed to respond both to the City of Portland’s stormwater management policy as well as to the public’s desire for the streetscape to be sustainable and green. In total, twenty-seven linear stormwater planters of varying sizes are proposed, each filled with low growing plant material to complete the streetscape experience. Once constructed, Denver Avenue will serve as a unique example of extensive green infrastructure built within an urban commercial district.

Projects like these are by nature very complex, with many variables to be taken into account when laying out the required street elements. Objects such as utilities, lights, benches, bike racks, and trees must all be considered to establish a pattern that gives the streetscape consistency in design but also meets the needs of adjacent property owners.

Adding stormwater planters into the mix significantly complicates the effort. Their layout has to take in to account businesses lining the street, so as not to create barriers that would adversely affect the function of entrance ways. Access from adjacent parking will be accomplished by providing a three foot wide paving strip between the face of curb and planter. Also, the project seeks to accommodate the creation of small outdoor spaces, strategically located along the furnishing zone, so that businesses can add outdoor sidewalk cafes. A less rigid and compromising approach had to be taken to meet these needs.

On many streets, a one block prototypical design is developed, which essentially is repeated with minor modifications to maintain a pattern. This was not the case on the Denver Avenue project. Location of planters was proposed as needed, and as a result, the distance between planters varies along the entire street. In addition, the sizes of the planters are varied, from twelve feet to eighteen feet long. In some instances, the planters are shortened to create a larger space in front of a building entrance; in some locations they are lengthened to pick up additional stormwater capacity. This is all proposed while taking account of existing utilities, placing new ornamental lights, and evenly distributing new street trees as best as possible.

An oblique perspective rendering of a typical block showing proposed street improvements for Denver Avenue Streetscape Improvements Project, including stormwater infiltration planters, widened sidewalks and bike lanes, new street trees, ornamental street lights, and public art. Image courtesy SERA Architects.

This was by no means a perfect process and difficult decisions were required to satisfy the needs of the City and the concerns of local residents, businesses, and property owners. However, the newly constructed Denver Avenue streetscape should provide a unique and exciting new green amenity for the Kenton neighborhood and hopefully be a catalyst for a new and prosperous era for the community. The Denver Avenue Streetscape Improvements Project will start construction in Summer 2009.


These projects do not work in every place. Rather, they tie into the local context and involve community input to make them fit and thrive in their urban context. Among the lessons to be learned from these projects are:  What are the ultimate goals of the renovations?  How far can established boundaries be expanded? And what is the role of a landscape architect in these processes?  Landscape architects are poised to tackle the myriad challenges, and suggest possible solutions to questions that can change gray infrastructure to multi-functional green infrastructure. This shift from gray to green requires not merely urban design or engineering skill-sets, but the ability to bring together and synthesize creative ideas, community input, and technical solutions, and translate them into vibrant, functional, and beautiful urban places.

Jason King, ASLA, is a landscape architect and Senior Associate at GreenWorks PC, a landscape architecture and environmental design firm based in Portland, Oregon. He can be reached at

Shawn Kummer is a Landscape Architect and Associate at GreenWorks, where he served as project manager and lead designer for the Denver Avenue Streetscape, 102nd Avenue, and Windscape Projects. He can be reached at  

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