We are super excited to share that DeepRoot and the Silva Cell have made it to the big time — or at least to the SF Streetsblog, which is the big time as far as we’re concerned.
An article by Matt Baume lucidly explains the bigger picture of what we’re trying to do, and sheds some light on why we may be having a hard time getting adoption of “green utilities” in our own hometown, even as the product and technology is being embraced by municipalities and developers across the rest of North America (and parts of Europe and Austalia).
The article quotes both Doug Wildman, Program Director with Friends of the Urban Forest, and Rosey Jencks, head of stormwater planning with the San Francisco Public Utilities Commission, expressing cautious optimisim about the Silva Cell while questioning whether it’s too new to be considered a proven technology.
While the Silva Cell itself is new — our first installation was in early 2007 — the technology behind it is not. Generically termed “suspended pavement,” this method for soil delivery to trees has in the past been achieved with custom concrete vaults. Like the Silva Cell, this creates a containment system for vast, lightly compacted soil volumes available for tree rooting and, if thus designed, for some stormwater management — but it’s an expensive option. The Silva Cell uses the exact same technology, but aims to do it on a modular, mass-producible, and easily customizable level. Street trees in downtown Charlotte planted twenty five years ago in a custom suspended pavement system are doing fantastically (scroll down to find the case study).
The other issue we get asked a lot about is cost. While we aren’t able to do cost analyses on most of our installations because we aren’t privvy to all the related expenses of streetscape rennovations (such as labor, excavation, and so forth) on any given project, we do have a few projects with detailed cost breakdowns and comparisons. One such analysis comes from our first commercial installation, in Kelowna BC. This article, by Ian Wilson, details a project where trees along three separate blocks of downtown Kelowna were planted in three different mediums — a standard tree pit, structural soil, and the Silva Cell.
Read all the way through to the end of the article and you’ll see that on this fairly typical, small-scale streetscape rennovation, structural soil is 2.71 times as expensive, and a standard tree pit it 2.69 times as expensive as the Silva Cell on a cost per cubic meter of soil basis. And that’s without taking in to account the significant environmental, psychological and stormwater value that trees bring to their communities.