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This is a soil cell being installed to grow a tree in the newly revised Piazza Park. It will hold planting soil for the tree’s roots, and be covered with concrete.
This is the location of the soil cell in above photo, as it appeared in 2023. The 2000 Piazza design interspersed pavement with natural planting areas throughout. This was done to create a “Garden Piazza” feel, and support a dense tree canopy to beat summer heat.
As I was walking past the Piazza Park in downtown Renton recently, I came across a friend who asked me about the unusual plastic honeycomb being installed in two locations near South Third Street. Before I could answer her definitively, I had to come home, search the City website, and check the plans.
These black plastic structures are soil cells, a 25-year-old invention to help trees grow in heavily-paved urban landscapes.
Street trees and other trees surrounded by pavement sometimes struggle to thrive because of compacted soil and shortages of water. Soil cells can help solve these issue by holding uncompacted garden soil and accepting drip irrigation water.
The downside is that they can cost about $10,000 each installed (which is a lot for one tree), and no one has more than 25 years of experience with them so there is no proof of their long-term life expectancy.
Most of Renton’s street trees still get planted the old fashioned way, by designing reasonably wide 4-foot or 6-foot planting strips, choosing a species with deep roots that does well in urban street settings, excavating a hole more than three times larger than the root ball and filling it with good planting soil, and using a water bag while it is getting established. Ideally the adjacent pavement is installed on “structural soil” –a mix of crushed rock and sandy loam– to accommodate mature root growth of the tree.
But the Piazza has recently seen two dozen of it’s significant trees cut down, and is going to be widely paved over with just small areas of grass and plants here and there. Its two water features have also been removed. So on hot summer days, visitors will flock to any shade they can find. Hopefully these soil cells work to grow at least a couple of big replacement trees.
(As I’ve covered before, I would not have chosen to spend $3 million rebuilding our 25-year-old Piazza Park, including taking out trees and water features. And even if directed to do so, I would not have started the project just ten months before we’ve asked the world to come see our downtown. But we are where we are, and I hope it is successful.)
A second soil cell is being installed for a new tree in the Piazza near South Third Street. This hole is just a few feet away from a 52-inch diameter water main owned by Seattle Public Utilities.
As can be seen from the permit drawing, the above excavation for the soil cell is a few feet from Seattle’s 52-inch diameter water main. The water main has approximately four feet of soil covering it. There is little margin for error. If either pipeline was ever errantly broken by heavy equipment, it could release 100,000 gallons per minute of water into downtown Renton, quickly flooding nearby properties.
Soil cell details shown in the permit drawing
Goodbye to the shade. Most of the tree canopy in this photo has been removed. (Photo looking South in 2023)
The trees and plantings in the background have all been removed. So has the fountain.
In this map of significant trees in the Piazza, the 23 trees with red dots were scheduled for removal. From my photos it appears that two or three additional trees may have been removed near the center of the Piazza.
It’s crappy, but you can’t have nice things and stinky, drug-addled addicts at the same time. Notice the closed restrooms? We collectively voted for this.
Thanks for bringing this up anonymous. This is often mentioned by the rumor-mill as the reason for eliminating the water features and much of the foliage from the Piazza, and I’ve been told that some officials have stated this as the reason for these changes. But for years the official plan for resolving these issues has been to keep the Pavilion open seven-days per week, including its public restrooms. Activating the Pavilion full time would increase community use of the Piazza, and surveillance over the Piazza to prevent illegal activities. It doesn’t need to be a paved parade-grounds to solve its problems. It can have trees and foliage, like the garden piazza we built in 2000.
In 2019 we had a proposal from Rain City Catering that would have kept the Pavilion building restrooms open, and wholesome community activity in the Piazza seven days a week, with no investment from the City of Renton. The award-winning caterers simply asked for an extended lease (that would last more than a year), and they were willing to immediately install a coffee house and deli into the building with their own funds, as well as add new signage to the building and paint the outside. The restrooms and indoor/outdoor continuous Pavilion activity would have ended the problems developing in the Piazza.
I liked the idea of a quick free solution to the Piazza bathroom and surveillance issues, and I know Rain City Catering could have delivered on it from their ten year track record working with the city. But the Mayor and Public Works director pushed hard on the Logan Market idea. That idea was supposed to also be free for the tax payers and include a large event space; but it has taken seven years so far, is now costing taxpayers $13 million, it lost it’s event venue, and apparently required (?) decimating the Piazza and all its trees and water features for it to work. And the city has of course lost our biggest event center in the process.
From my perspective, most of the problems that the Piazza has suffered since 2019 have been self-inflicted by the city’s top leadership, since we could have fixed it back then with a long-term lease.
Rain City Catering’s 2019 proposal is the one known as the Pavilion 2.0 concept discussed in detail in this blog entry here.
Your solution well may help, but across the city we have closed restrooms because we’ve collectively decided that drudged out jerks (and the grifters that support them) are vastly more important that families, citizens, children, and the truly vulnerable.
And we’ve decided this over and over by voting for this over and over.