Tanner Springs: A Tonic of Wildness

Tanner Springs is a laboratory that will determine if a restored natural habitat can thrive in a dense urban environment. This week volunteers joined members of the Portland Parks and Recreation (PP&R) to plant over 300 native grasses and shrubs in areas overrun by “Ecological Disrupters,” invasive plant species that degrade wildlife habitat.  Ecological Disrupters are mostly “weedy” non-native plants (e.g. English Ivy) that have aesthetic appeal in a yard, but create biological deserts when they take root in natural lands.  The Tanner Springs Management Plan’s “zero tolerance” policy requires their removal.  Ecological Disrupters are also eradicated in Forest Park, but Tanner Springs is a different type of park, it is a human creation.

English Ivy in Forest Park

The square block park was once part of the marshy Willamette River floodplain where Tanner Creek flowed into Couch Lake.  Over a century ago, the creek was buried in a sewer line and the area was filled to provide land for a rail yard.  In 2003 the site was reinvented once again.  By then, the development of the Pearl District was in full swing.   After Jamison Square opened in 2000, the Portland Development Commission sponsored a series of charrettes to elicit citizen input for the park being planned two blocks to the north.  It was determined that a water feature and access to nature were essential to a vision would set Walden Pond in the midst of the city.

Notice Couch Lake at terminus of Tanner Creek

Atelier Dreiseitl (Germany) and Green Works, P.C. (Portland) was commissioned to design Tanner Springs.  The idea was “to peel back the skin of the city” and create a native plant-dominated park that paid homage to the lost wetlands.  Water is pumped to the highest elevation, and it is released into two runnels that follow a sloping topography that drops six feet.  The runnels branch into a series of rock-edged rivlets that flow`into a low-lying pond.  The rocks were arranged to tune the trickle of water into a natural harmony, an attempt to engage the senses the city deadens.  This system provides an ecological function as well.  Stormwater from the surrounding block is filtered through the site’s hydrologic system, and the funneled underground to be treated with UV lights. 

Tanner Springs is also a work of art. A 12-foot high wall of 368 undulating recycled rail ties borders the pond.  Chunks of cobalt-blue art grass were fused into the rails, each hand painted by Herbert Dreiseitl with abstractions of lost wildlife.  Grassed terraces on the north and south sides of the park mimic stadium seating to observe “the game of nature” at play.

In 2005 Tanner Springs Park opened to much acclaim. The New York Times described it as “a sort of cross between an Italian piazza and a weedy urban wetland with lots of benches perched besides gently running streams.” The “weedy urban wetland” was actually three distinct landscapes: (1) lawn and landscaping (2) grasslands and (3) marsh.

Three planting zones: Lawn, grasslands, marsh

After a decade, Tanner Springs remains a work in progress.  It requires constant weeding and analysis, as maintaining natural habitats on a site affected by soil contamination and a high water table is challenging.  5,000 cubic yards of soil saturated with oil and heavy metals was removed, and a one to two-foot layer of compost and topsoil now underlies the grassland areas, which are the most difficult to maintain.  Hardy xeric shrubs from Eastern Oregon have fared the best, as they have adapted to the site’s poor soil and minimal shade.  Water percolation was also hampered, and an underground pipe was installed to run water from the pond to the head of the runnels. 

This spring and summer volunteers invested over 400 hours removing Ecological Disrupters, restoring the flow and harmonic tunes of weed infested runnels, and studying the park’s idiosyncrasies.  Michelle Shapiro, a heady field botanist, heads the volunteer group and she worked with PP&R horticulturist Robin Akers and botanist Erin Riggs crafting a plan to rejuvenate the park’s degraded grasslands.  To enhance the charachter of the park, they utilized native plants that “grow with vigor, work together to crowd out weedy species, and require minimal irrigation.” If Portland is to truly be sustainabile Tanner Spring will be just one in a myriad of native habitats, an early point of reference in a rich and diverse landscape.    

Tanner Springs is an exercise in ethics, as well as ecology.  It provides the “tonic of wildness” that Thoreau deemed necessary to mitigate the incessant intrusion of commercial society.  “When an osprey snags a koi ten feet away from a shallow pond or a great blue heron walks through a created wetland in one of the city’s densest neighborhoods it’s a transformational experience for a five-year old,” Portland urban naturalist Mike Houck writes.  The park is fostering for all ages what Aldo Leopold called an “ecological aesthetic.” The famed ecologist believed discerning beauty in the functions of a healthy environment was crucial to human survival.  This premise centers The Sand County Almanac, the “bible” of modern ecology that documents Leopold’s attempt to transform a played out farm on the Wisconsin River into a viable natural habitat.  Tanner Springs Park is a similar experiment, and its stewards are equally resolute. 

As the new planting takes root, beauty will take form on ecological lines.  At a time when climate change has placed nature in flux, Tanner Springs offer a place of repose, a modern version of Walden Pond.  Here one can contemplate wildness and learn, as Thoreau did, that “It’s not what you look at that matters, it's what you see.”