What is Silva Cell?

The DeepRoot® Silva Cell® is a patented, modular, suspended pavement system that integrates water, soil and tree roots and delivers on-site stormwater management through bioretention. DeepRoot’s Silva Cell system can be designed for surface water management by constructing a bioretention system within the Silva Cell modules. A typical bioretention system consists of:

·       A ponding layer to store surface water runoff prior to treatment through the treatment media

·       Treatment media which filters the surface water and removes solids, organic and non-organic particles

·       Aggregate storage to convey the treated flow to the outlet or stored before infiltration to the surrounding soil

·       An overflow structure to prevent surface flooding during exceedance conditions

How can it be modelled?

Flow is a hydraulic modelling package for the design and analysis of optimal, compliant and cost-effective storm and foul water drainage networks, developed for organisations looking for a robust, intuitive and complete solution.

For more information and support with Causeway Flow, please visit www.causeway.com.

Options modelled:

Two basic options for the Silva Cell System are discussed for modelling in Flow, one is the Silva Cell 2X option and the second is the Silva Cell 3X option (shown below). Both systems have a similar make up of layers within the Silva Cell, but vary in the overall depth of the system.

Design steps:

1. Open the Storage Menu and select structure type as Soakaway.
2. If allowing infiltration from the Silva Cell, enter the site infiltration coefficients.
3. Enter overall porosity for the Silva Cell. Enter 0.506 for a Silva Cell 2X system with 300mm of ponding depth. Enter 0.448 for a Silva Cell 3X system with 300mm of ponding depth and 100mm of gravel drainage.
4. Enter the invert level of the system. This will be either 1.184m below cover level for the Silva Cell 2X system or 1.492m below cover level for the Silva Cell 3X system.

5. Enter overall dimensions of the Silva Cell System, including the tree area. The pit width and pit length should be estimated in the first instance and might have to be adjusted after the simulation to either prevent flooding or reduce costs. The pit depth will be 0.784m for a Silva Cell 2X System or 1.092m for the Silva Cell 3X System.
6. Enter the available depth of the Silva Cell System that can be used for infiltration.
7. Enter ‘1’ in the Number Required input box.

Once the information is input, you can run simulations of the drainage design and optimise the size of the Silva Cell system.

Data from DeepRoot

DeepRoot have created a Stormwater Design Tool which can be used to estimate the size of your Silva Cell system before entering it into your Flow software. It can also be used after modelling to understand the number of Silva Cell modules required for the area of bioretention required.

Support

For additional support from DeepRoot, please refer to our resources section for more information on the Silva Cell or contact [email protected].