Blogging about the 2010 American Society of Landscape Architects Annual Meeting and Expo, September 10-13, held at the Convention Center in Washington, D.C.
For years I’ve been hearing bits and pieces about the massive, multi-billion-dollar project to fix Dallas. No, not everything about Dallas, just one of its biggest challenges – creating parkland along its river, the Trinity.
This is the story that came out, in fits and starts, in that riveting ASLA workshop, told by landscape architect Ignacio Bunster-Ossa, engineer James Parrish, park official Willis Winters and park advocate Gail Thomas. Each focused a bit tightly on his or her specific issue, but ultimately, prodded by some audience questions, the full story in its complexity came through.
Dallas’ problem is a doozy and its solution is a double-doozy, although whether it’s sustainable is another question.
The challenge of the Trinity River, like other desert waterways, is that it fluctuates wildly from the usual trickle to the occasional roaring deluge. Building the surrounding city to respect the deluges means pulling the buildings and streets hundreds or thousands of yards back from the regular river channel, leaving a wide swath of deadening nothingness. Conversely, building the surrounding city right up against the normal trickle means courting periodic catastrophic floods.
Dallas, with the help of the U.S. Army Corps of Engineers, has split the difference, building quite a distance away from the river (but not really far enough for true flood safety) then adding high levees to protect against the worst of the crests. This leaves a wide stony area alongside the river, relegated historically to an out-of-sight, out-of-mind status by the high levees.
If Dallas were an eastern or northern city, the Trinity would have a broad greenspace alongside it, as Washington, D.C. has alongside the Potomac or Minneapolis by the Mississippi. But there’s not enough rain in Dallas, and irrigation for a big park would be way too expensive. However, there is one source of water for a Trinity River Park — the sinks, bathtubs and toilets of the 1.2 million residents of Dallas. Turns out that the city’s wastewater treatment plant produces about 50 million gallons of relatively clean water per day. That regular flow enters the Trinity, day in and day out, but it does so downstream from downtown. That’s enough water not only to irrigate a park but to actually create a brand new lake in the normally dry gulch, as well.
A big part of the story is political — how a controversial multi-billion-dollar project got through the political process, beginning as a highway program and gradually morphing into something ecological and place-making over the decades. Other big issues involve engineering — how to design a lake that doesn’t stagnate and eutrophy between floods; and also how to make a park inviting to users without breaching the high concrete levees that surround it. The answers are complex (one seems to involve tilting the lake’s bottom so that it flows upstream), and I’m heading to Dallas in November for the 21st Century City Conference to try and understand them better.
But one big question — the 50-million-gallon question — didn’t come up. The cleaned wastewater, upon which rests this whole perpetual motion machine, will need to be pumped uphill about three or four miles.
I’ll be the first to admit that many if not most urban parks aren’t traditionally sustainable. I’m sure that if the power were shut off in Chicago’s Millennium Park or San Francisco’s Golden Gate Park or Houston’s Buffalo Bayou all kinds of things would go haywire. But I also know that one of the most basic rules of infrastructure is that water flows downhill.
Interestingly, 1,000 miles west of Dallas, Phoenix has a similar problem but deals with it differently. There, so much water is taken out of the Salt River that it actually dries up above the city and there is nothing but a wide empty gully through town. Then, downstream it reappears, thanks to the city’s wastewater treatment plant. Phoenix hasn’t tried to create a lake in the city, but it has used the sewer outflow in a network of manmade wetlands to attract wildlife.
Phoenix started with one big physical advantage over Dallas — the city’s downtown wasn’t built near the Salt River and has no real connection to the waterway. Now it has two: its river-and-park solution comes a lot closer to sustainability.
The only way Dallas’ new Trinity River Park will ever be sustainable is if the power used to pump its life-giving water is generated renewably, using solar or wind. This is another reason for park advocates and clean energy advocates to work side-by-side together.