ASLA Oregon LANDbytes NOVEMBER 2011 Feature:
Phytoremediation in Landscape Architecture: It’s a Park, It’s a Wetland, It’s a…..?
By Jeff Boggess
Many common everyday trees, shrubs, perennials, and even invasive weeds like Indian Mustard and Pennycress have the remarkable ability to absorb and chemically breakdown nutrients like nitrate and ammonia, and even harmful elements like lead and arsenic. These plants concentrate and remove pollutants that would otherwise potentially continue to spread through soil, air, and groundwater. For example, arsenic is sometimes left behind in agricultural soils by herbicides and pesticides, but can be remediated by Chinese Brake Fern, which is able to absorb large amounts of arsenic within its fronds. Although plants and the micro-organisms that inhabit their roots have been providing this service since the beginning of time (most notably through the absorption of CO2 gas and release of breathable oxygen), only recently have these cleansing abilities become an established science and designated ‘phytoremediation’ - the process of using plant-based strategies to clean air, water, and soil.
Instead of relying on conventional methods that can be environmentally disruptive, financially costly and energy intensive, phytoremediation simply capitalizes upon basic plant biological processes, and the constant natural flow of elements from soil to roots as food. Luckily for us, many plants aren’t particular about whether these elements are found naturally occurring in the soil or added by humans. Pollutants are taken up by the plants roots where they are chemically modified through the plant’s metabolism and evapotranspired as harmless gas, or they are stored within the plant’s biomass which can then be harvested and processed. With the removal of harmful substances, we are able to benefit not only from cleaner air, water, soil but also prolonged habitat improvement, and the enhancement of diversity and vitality in urban and rural areas by integrating phytoremediation into public space.
Portland and the Willamette Valley offer many outstanding case-studies where landscape architects and engineers have collaborated to integrate phytoremediation sensitively into both urban and rural contexts. From “Green Street” stormwater facilities, to first-of-their-kind, large-scale poplar plantations, projects in this region explore the boundary between functional facilities and designed public amenities. In Portland, the abundance of curbside stormwater planters, like those that can be found along bike boulevards, validate the design ability of Oregon landscape architects and engineers, who depend on support from the local government and from Portlander´s unique willingness to invite these features into their daily lives for the sake of the common good. With that said, it’s no wonder that the International Phytotechnology Society chose Portland this year as its venue for the 8th Annual International Conference.
Portland´s reputation for visionary stormwater and wastewater management has reached an audience extending well beyond the Northwest, being confirmed by the enthusiastic scientists, practitioners and government officials who were in attendance at the Conference coming from faraway places like the Netherlands, India and Malaysia. The idea of ¨Portland Sustainable Design¨ in the minds of these individuals seemed almost like a brand in itself, akin to ¨German Precision¨ that they had come to soak up and take home for application in their own cities and towns.
Where other workshops during the week focused on smaller scale examples of phytoremediation like green roofs, rain gardens and other forms of urban stormwater facilities within the Portland area , the one in which I took part traveled into the Willamette Valley and visited 5 large-scale wastewater treatment applications. Renee Stoops of SPROut (The Sustainable Plant Research and Outreach Center, the hosting organization of the Conference for the week) guided our group by bus to two Poplar Remediation Plantations; Woodburn Waste Water Treatment Plant, and the Riverbend Landfill which treats effluent/biosolids and landfill leachate respectively, and three constructed wetland projects treating effluent coming from wastewater treatment facilities (Albany Talking Water Gardens, Willowlake Treatment Plant, and the Oregon Garden). The facilities represented an interesting progression over the course of the day from purely pragmatic places of remediation in the form of row after row of poplars growing behind chain link security fences and going quietly about their business of absorbing wastewater, biosolids and leachate; to constructed wetlands that were functional not only in their treatment capabilities, but also invited the public with pathways, waterfalls, seating areas, and interpretive signage.
Bringing phytoremediation into the public realm blurs the boundary between science and design and becomes an intriguing point-of-connection between biology and landscape architecture. Although this was done voluntarily in the projects visited during the workshop, in the future, particularly in urban areas, this approach will likely become a necessity as open spaces that can serve these two invaluable purposes (remediation and public amenity) independently become scarcer. Leading international landscape architects like Michael Van Valkenburgh and James Corner are two of many that are already capitalizing on this relationship, bringing a new layer of credibility to the holistic, contextual, stewardship-driven approach which the landscape architecture profession prides itself on. Parks, streets and gardens must continue to be designed for human-friendly enjoyment and retreat, but they also have the potential for meaningful enrichment by becoming places of sustainable renewal and investigation.
With local projects like those showcased at the Phytotechnology Society Conference demonstrating Portland as an international leader in the field, what better place than here to continue to promote the ¨blurred¨ landscapes that combine science and design? The Northwest region is recognized as a hub of sustainable design and we should consider the role landscape architects might play in the advocacy and distribution of these visionary ideas. Along with the landscape architect’s understanding of space, circulation, programming, planning, ecology and plants, phytoremediation adds the next layer of significance to the landscape and may push us into a new chapter of the profession.
Whitney Water Purification Facility, by Michael Van Valkenburgh Associates, Inc.
with Steven Holl Architects, New Haven CT
Poplar Remediation Plantation, Woodburn Wastewater Treatment Plant, Woodburn OR
Albany Talking Water Gardens, Willowlake Water Treatment Plant, Albany OR