The Zidell Yards site was selected as one of five pilot eco-districts in Portland, Oregon. The landscape architect led a collaborative, workshop-driven planning process to develop three distinct scenarios. The following three scenarios apply green infrastructure solutions that capitalize on infiltration and surface conveyance with the goal of exceeding existing regulatory requirements for stormwater management and providing creative brownfield remediation solutions with multiple community benefits.
At 33 acres, the Zidell Yards site offers the first comprehensive opportunity to identify solutions for the application of green infrastructure on one of the largest brownfield remediation and redevelopment sites in Portland, Oregon. The goal of this effort was to develop a range of comprehensive solutions for the application of green infrastructure within a brownfield redevelopment.
The design team developed the following list of goals for success on the project:
- Provide flexible and adaptive solutions for the specific conditions of a remediated brownfield
- Support the Environmental Protection Agency’s Strategic Agenda for Green Infrastructure
- Evolve current sustainable stormwater management techniques
- Explore a range of green infrastructure concepts
- Minimize or eliminate the need for new piped outfalls to the river
To develop the most credible and thorough scenarios, each plan had to act as a stand-alone solution to meet the goals of the project and design assumptions. The landscape architect guided the focus on comparisons of a dispersed network versus a concentrated network of green infrastructure solutions. This comparison provided the foundation for the three scenarios that were developed to investigate the range of methods needed to embed green infrastructure in a future brownfield development. The team used a conceptual master plan provided by the owner was used as the basis for sizes and locations of general site elements such as buildings, plaza spaces, and roadway networks. A green infrastructure network was then applied to the framework of the master plan according to each scenario’s theme.
The three scenarios developed for the project were: → Diffuse + Embedded → Clustered + Distinct → Central + Focused
The Diffuse + Embedded scenario collects, conveys, and treats stormwater adjacent to where it falls on Zidell Yards. As an evenly distributed network, the site’s green infrastructure maximizes stormwater infiltration through an integrated network of techniques including ecoroofs, porous paving, and small-scale vegetated facilities. The stormwater collection and infiltration system relies on a network of small-scale vegetated facilities that mimic a native wetland. The basins are linked through an interconnected network of v-channels, swales and trench grates that collect and convey stormwater throughout public and private land. This concept could be applied as a performance-based approach with a specific, defined plant palette to ensure that each future building can be knitted into the existing pattern of the system. The dispersed network allows for maximum flexibility to work around specific brownfield conditions. The collection capacity of the Diffuse and Embedded system fosters many secondary distributed benefits, such as rich pockets of vegetation and opportunities for storage and water reuse for building functions and irrigation. The distributed application of these green infrastructure techniques provides a unifying identity and sense of place.
The Clustered + Distinct scenario incorporates components of both centralized and distributed systems by managing stormwater at a subdistrict, or neighborhood scale. This management technique is uniquely tailored to groups of buildings to create distinct management areas or neighborhoods. The system would rely on 12 inch-deep, urban stormwater planters that may be more expensive to construct than the shallow facilities, but provide more efficient footprint for management of stormwater. The visibility of stormwater in the conveyance network would occur as smaller storm events would be conveyed from rooftops, across plazas, and to the vegetated planter. This concept would provide flexibility for developing smaller, subdistrict stormwater networks as development occurs over the next 15 to 20 years. This smaller network would allow for a reduced initial capital investment while maximizing the efficiency of construction of only a handful of larger facilities.
In the Central + Focused scenario, stormwater is conveyed through a network of open channels to large, centralized, district-scale facilities. Three subwatersheds collect stormwater from buildings and pavement areas before treatment and infiltration in the large and integrated facilities. The stormwater facilities take the form of 24-inch-deep geometric stormwater planters that are integrated with the surrounding plaza spaces. The reduction of green roofs and pervious pavements provides more frequent filling of conveyance channels during smaller storm events, increasing the visibility of water. Overflow from larger storm events is conveyed to a series of weirs to discharge runoff via overland flow to the Willamette River. The larger size of this green infrastructure enhances the visual, recreational, and habitat value of the water being conveyed.
The green infrastructure design principles presented here are not limited to brownfield sites but can be transferred to new development, redevelopment, and infill settings. Each of the scenarios offers viable alternatives for green infrastructure implementation in public and private spaces, and elements of the scenarios can be mixed and matched throughout the site as development begins, if desired.
Because of its high visibility, strong public interest, and the significance of this project to pave the way for stormwater management throughout the city, this project is receiving strong support across all city bureaus and with our elected officials. Zidell Yards property is a desirable location on the waterfront and will also be a hub for mass transit activity, including a new light-rail line and stop, an expansion of the Portland Streetcar, and a new pedestrian bridge across Interstate-5 to residential neighborhoods. The Zidell Yards project is an ideal showcase for highly visible, innovative, multi-benefit stormwater management that residents and visitors can experience and enjoy daily. This effort is just the beginning of a broader conversation that will continue as we study and apply green infrastructure and brownfield redevelopment. As more former industrial properties are redeveloped across the nation, the design community will come to understand the opportunities and limitations of various green infrastructure approaches and be able to test innovative stormwater solutions in areas previously considered off limits because of contamination.