1: Can Silva Cells go around utilities?

Yes, our modules can be moved and oriented to accommodate most utilities, footings, and other obstacles. Integration with utilities is by no means a barrier to using Silva Cells! Silva Cells are designed to be completely structurally independent, meaning it is not necessary for them to be in a linked matrix for support. The space between Silva cells are adjustable and when combined with our large module size (which offers significantly more room for routing utilities through the cells), makes going around, over and under utilities simple.

SMUD HQ_Sacramento project coupling utilities and Silva Cell, surrounded by geogrid.

When utilities are too large to be run though the soil within the Silva Cells and aggregate gaps may be used or a shorter module can be used to “step” over or under the utility while maintaining a connected soil volume. DeepRoot’s technical team is always happy to help you design your system around exiting or proposed utilities and can provide completed shop drawings for your project. We’ve seen it all, from the smallest footing to the largest duct bank.

2. Can Silva Cells be cut?

We do not advise cutting or modifying individual Silva Cells in any way. Silva Cells are a structural element and altering them leads to an unknown redistribution of force on the unit. Without testing that simulates the exact field conditions for each project, it’s very difficult to conclusively know how cutting or otherwise modifying a Silva Cell might impact the remaining portions of the structure. The good news is that the need to cut a Silva Cell should not arise. Due to the modularity and structural features listed above, the cells can be easily arranged around any obstacle.

3. Can DeepRoot Silva Cells be used around existing trees?

Silva Cells can be used on sites where existing trees need additional soil volume. First, a local arborist should evaluate the trees and determine if root pruning is an option and how much the roots can be cut back without impacting the health of the trees. The Silva Cells can then be installed as close to the tree as the root pruning will allow. If possible, it is beneficial to keep any supporting roots that can pass through the new Silva Cell system similar to how you would build our system around a conduit.

It is important to understand that the tree pit for a retrofit will be much larger than a tree pit for a newly planted tree due to the extent of the tree’s roots. Tree openings need to be sized proportionally to the size of the root mass.

Using Silva Cells for a retrofit is often more costly than a traditional installation. Excavation costs are generally higher as the roots must be treated carefully and hand digging will likely be required in some areas. However, when working with valuable or historically significant trees, this extra effort is worthwhile. More in our existing tree blog posts part i and part ii.

4.Why Geogrid around the perimeter instead of Geotextile?

The purpose of the geogrid is to separate the compacted backfill from the uncompacted planting soil within the Silva Cells and provide support in areas of transition. Geogrid offers the amount of strength needed to hold back backfill and other soils from the soft, uncompacted soil filling the system. While geotextile could also be used in this way, tree roots are unable to pass through geotextile material, thus forever limiting the tree to the space provided in the Silva Cell system. Geogrid allows roots to exit the Silva Cell system and expand into the surrounding area over time. In short, either geogrid or geotextile may be used around the perimeter of the Silva Cell system but only geogrid will allow the roots to reach beyond the system as the tree grows.

5. Is installing DeepRoot’s Root Barrier important?

Root Barrier product has vertical elements that direct tree roots down and away from hardscapes, preventing costly root damage while preserving the health and beauty of mature trees. When used with the Silva Cell system, a root barrier directs the roots down and into the soil within the Silva Cells. An installation without a root barrier risks the roots making their way into the pavement profile, causing damage to the pavement and/or aggregate base layer. By directing the roots into the soil within the Silva Cells, not only is pavement damage avoided but the tree is able to access the nutrients and water provided in the soil. DeepRoot’s Root Barrier has ground lock anchors that hold the root barrier into the soil and prevents ground movement from pushing the root barrier back up out of the ground. Using a root barrier on your project is a simple way to ensure your trees find soil and resources without damaging surrounding paved areas.

Function of Geogrid.

6. Do I need an underdrain?

Underdrains are necessary in applications where water is artificially introduced into the system. If your project uses permeable pavement, has surface run off piped into to the system, directs water to the tree openings via curb cuts etc., and underdrain should be used. In northern climates where road salt is used, having an underdrain helps the spring rain flush excess salts out more efficiently.

Silva Cell and Underdrain and Utilities Cohabitating

When it comes to non-permeable applications where the only water entering the system (other than irrigation) is what lands in the tree openings, having undrains is based on factors like risk of oversaturation, added cost of installation, and availability of a suitable outlet. If you have questions about whether your project needs an underdrain, contact us!

7. Can DeepRoot’s Silva Cell system be used with any tree?

From our perspective, yes. Any tree can be used. Silva Cells have been used successfully with many tree species from live oaks to palm trees. Any tree well suited to the location it will be planted may be used with Silva Cells.

Because we install projects all over the world, we defer to local designers and arborists to determine appropriate species for each project. Some communities also have a species diversification plan that determines what species of trees are acceptable to use in the area. We are ready to assist you with your project, please email us at [email protected] to connect with a DeepRoot team member today.

Tree Diversity at Lincoln Road Project in Miami, FL. Courtesy of Raymund Jungle