The City of Santa Rosa’s goals at the courthouse square was to protect stormwater flows into the Santa Rosa Creek and to retain as much rainwater onsite as possible for as long as possible. The city’s stormwater rules state that projects that create more than 10,000 square feet of impervious surface area must add features that reduce and treat stormwater runoff.
Number of DeepRoot Silva Cells: 1050 2X
Average Soil Volume per tree: 300 ft3
Installation type: Integrated Trees, Stormwater, Plaza
Number of trees: 87
Project Designer: Carlile Macy
Contractors: Thompson Building Corp.
Installation date: 2016
Challenge | Solution
To meet Santa Rosa’s project goals landscape architect firm Carlile Macy, chose DeepRoot Silva Cells. “We were drawn to the Silva Cells as the best solution to provide for growing healthy urban trees,” said Curt Nichols, Carlile Macy, “When we realized that the Silva Cells were also capable of providing the required stormwater treatment, it became even easier to justify the additional investment as being able to address two goals of the project with a single design solution.”
To satisfy the city’s stormwater rules, Carlile Macy handled the requirement in two different ways: by using GraniteCrete, a product similar to decomposed granite to allow infiltration of water along walkways and by using pavers made of permeable material. The pavers are strong, fast draining, and very low maintenance.
In addition to the 45,000 permeable surface materials, Silva Cells provide 300 ft3 of uncompacted soil for each of 87 new trees planted in the plaza. They also provide storage area for stormwater, which percolates the soil within the cells and is consumed by the tree or absorbed into the soil, excess water is routed into a storm drain. The Silva Cells are equipped to bear the load of the pavers as well as traffic by humans and other vehicles during events like concerts, farmers markets, and emergency situations.
Also key to the project was an effort to preserve healthy, existing trees, Carlile Macy included this notion in their master plan. The design saved several of the existing large redwoods and one 150-year-old Bunya-Bunya tree.
“A primary design element of Courthouse Square are the tree bosques which are intended to frame the square with leafy green areas of shade providing shelter and refuge from the sun on warm summer days while also providing a paved, permeable surface underneath able to withstand the heavy public use of an urban square.”
Today the newly redesigned Courthouse square features a number of sustainable design elements. Custom programmable LED light columns, electrical plug-ins, a Wi-Fi hub, trees, and green space, and more. The new layout helped revitalize Santa Rosa’s downtown core by attracting more pedestrian traffic and business to the surrounding area by providing an environment that fosters community in an urban setting.